REVIEWS
ELSEVIER
Earth-Science Reviews 52 (2001) 333-369
www.elsevier.com/locate/earscirev
Response of interior North America to abrupt climate oscillations
in the North Atlantic region during the last deglaciation
b
Zicheng Yu a, * , H.E. Wright Jr. b
a Canadian Forest Service, 5320 122 Street, Edmonton, Alberta, Canada T6H 3S5
Limnological Research Center, University of Minnesota, Minneapolis, MN 55455, USA
Received 10 May 2000; accepted 29 September 2000
Abstract
Several broad-scale climatic oscillations during the last deglaciation are well documented in regions around the North
Atlantic Ocean. This paper reviews empirical evidence for these deglacial climatic oscillations from non-coastal North
America and discusses implications for testing climatic simulations and for understanding the cause and transmittal
mechanisms. Paleoclimatic interpretation of oxygen-isotope records from several small sites in the eastern Great Lakes
region indicates a classic deglacial climatic sequence that is comparable with records from Europe and Greenland. The
climatic events as interpreted from Crawford Lake oxygen isotopes include the B¢lling-Aller¢d (BOA) warming at
-
12,700
12,500-10,920 14C BP, an intra-Aller¢d cold period shortly before 11,000 14C BP, a
10,920-10,000 14C BP, the Holocene warming at 10,000 14C BP, a brief
9650 14C BP, and an early-Holocene cold event at 7500 14C BP (8200 cal BP). Some of these
14C BP, a warm BOA at
cold Younger Dryas
(YD)
-
climate reversal at
Preboreal Oscillation (PB) at
events were also evident from changes in upland and aquatic vegetation and sediment lithology. The pronounced YD
climatic reversal has been documented from pollen records along the ecotones at this time and from glacier readvances in the
Great Lakes region. Along the Rocky Mountains from Alberta to Colorado, the YD event is indicated by alpine glacier
advance and/or shift in timberline vegetation. In Minnesota and upper New York, early-Holocene climatic instability is also
suggested by oxygen-isotope records and/or varve thickness. The regional variations in evidence for the YD and other
events in North America suggest that climatic oscillations may have different expressions in paleo-records, depending on
geographic location and characteristics of a particular site. The extent and magnitUde of these climatic oscillations across
North America suggest that these oscillations are an expression of climatic change that was probably widespread rather than
locally induced by a nearby glacier. The location of these sites implies that climatic signals were likely carried over the
Northern Hemisphere through the atmosphere, as indicated by general circulation models. We hypothesize that the lack of
evidence for a cold
YD
in interior North America west of the Great Lakes region and east of the Rocky Mountains was
caused by the trapping of cold arctic air mass north of the Laurentide ice sheet and by uninterrupted northward expansion of
warm Caribbean air; this strongly contrasted climate also produced non-analogous biological assemblages. © 2001 Elsevier
Science B.Y. All rights reserved.
Keywords: North America; Late glacial; Younger Dryas; deglacial climatic oscillations; mUltiple proxy paleorecords; air-mass distribution;
Amphi-Atlantic climatic contrasts
*
Corresponding author. Tel.: +1-780-435-7304; fax: +1-780-435-7359.
E-mail address:zyu @nrcan.gc. ca ( Z. Yu).
0012-8252/01/$ - see front matter © 2001 Elsevier Science B.Y. All rights reserved.
SOOI2- 82 5 2( 0 0)0 0 0 32- 5
PII:
z. Yu, H.E. Wright Jr./ Earth-Science Reviews 52 (200]) 333-369
334
These deglacial climatic oscillations have been
well documented around the North Atlantic Seaboard,
but until recently few studies have addressed the
continental interior of North America (Rind et aI.,
1986; Shane, 1987; Wright, 1989; Peteet, 1995).
Establishing the geographic extent and relative mag­
nitude of these deglacial climatic oscillations is es­
sential for understanding the mechanisms and causes
of these abrupt climatic changes in particular and of
Earth's climatic system in general. Here we review
recent multiple proxy studies from non-coastal North
America. The objectives of this paper are: (0 to put
evidence for deglacial climatic oscillations from inte­
rior North America in the context of other regions;
(2) to evaluate the transmittal mechanisms and to
explain the contrasting response of the continental
interior; and (3) to discuss strategy and future direc­
tions for obtaining empirical paleoclimatic records.
The paper will first provide a brief overview of
deglacial climatic events from regions around the
North Atlantic and from the west coast of North
America. We then focus on evidence from interior
North America, which has lacked examples of
deglacial climatic oscillations. Lastly, we evaluate
the ultimate and proximate causes and mechanisms
of transmittal based on a coupled ocean-atmosphere
general circulation model and propose a hypothesis
that explains the contrasting late-glacial climates be­
tween the Atlantic region and the North American
continental interior.
The time period covered in this paper spans the
late-glacial and early Holocene. The late-glacial here
refers to the time period of - 13,000-10,000 14C
BP, which is characterized by extreme climatic insta-
1. Introduction
In the North Atlantic region, the large and abrupt
climatic oscillations that characterized the last glacia­
tion continued into the last degJacial period. These
oscillations include quasi-periodic millennial-scale
Dansgaard-Oeschger (D-O) events (- 1500-year
spacing) and related low-frequency Heinrich-Bond
cycles (Dansgaard et aI.. 1993; Bond et aI., 1993,
1997; Bond and Lotti, 1995; Grootes and Stuiver,
1997; Mayewski et aI., 1997; Alley, 1998; Alley and
Clark. 1999). During the last glacial-interglacial
transition, the most recent manifestation of these
millennial- and century-scale climatic events was
broadly experienced in both Europe and North
America (e.g., Lotter et aI., 1992; Levesque et aI.,
1993; Bjorck et al., 1996; Yu and Eicher, 1998; Von
Grafenstein et al., 1999). These climatic events in­
clude the B�lling warming at 14,600 cal BP (12,700
14C BP) and the gradual cooling trend toward the
Younger Dryas (YD) climate reversal, which can be
regarded as the last Bond cycle. During the general
cooling trend of the B�lling-Aller�d (BOA) warm
period, several century-scale oscillations include the
Older Dryas (OD) and the intra-Aller�d cold period
(IACP; also called Gerzensee or Killarney Oscilla­
tion). In the early Holocene, Preboreal Oscillation
(PB) and 8200 cal BP cooling events have been
widely recognized in paleoclimatic records (Alley et
aI., 1997). The YD event is an abrupt and very
marked millennial-scale cooling episode between 11,000 and 10,000 14C BP. It is regarded as the latest
Heinrich event (HO) and has been more extensively
studied than previous ones.
Table
I
Ages of deglacial climatic events in the North Atlantic region (from Mangerud et al.,
1974; Wohlfarth, 1996; Bjorck et al., 1998)
Calendar age for the onset
Mangerud et al.'s (1974)
Radiocarbon age
Bjorck et a\"s
chronozones
(years BP)
event stratigraphy"
(GRIP year BP)
Holocene
11 ,50012,65012,90013,15013,90014,05014,70016,900-
Preboreal
10,000-9000
11,000-10,000
11,800-11,000
Younger Dryas
Alleriild
(1998)
GS-l
GI-la
GI-lb (IACP)
GI-l c
Older Dryas
Biillling
Oldest Dryas
>
12,000-11,800
13,000-12,000
13,000
GI-ld
GI-l e
GS-2a
"GS - Greenland Stadial; GI - Greenland Interstadial; IACP - intra-Alleriild cold period.
z. Yu, HE Wright Jr. / Eanh-Science Reviews 52 (2001) 333-369
bility and includes classic European chronozones
B�lling (13,000-12,000 14C BP), Aller�d (11,80011,000 14C. BP) and YD (11,000-10,000 14C BP)
(Mangerud et al., 1974; Wohlfarth, 1996). The tenni­
no logy of Mangerud et al. (1974) is used here for
convenience. Recently, Bjorck et al. (1998) proposed
a new late-glacial event stratigraphy for the North
Atlantic region based on the stratotype of the Green­
land ice-core isotope record (GRIP). Their event
stratigraphy extends from the beginning of the
Holocene downward, including events Greenland
Stadial l (GS-I ) for the YD, Greenland Interstadial 1
(GI-I) for the Aller�d and B�lling, and GS-2 for the
Oldest Dryas. The GI-l is further subdivided into
episodes GI-l a (warm period between YD and
IACP), GI-lb (IACP), GI-l c (warm period between
IACP and OD), GI-ld (OD) and GI- l e (B�lling
warm period). Table 1 lists radiocarbon and calendar
ages of deglacial climatic events and correlation of
the Mangerud et al. (1974) tenninology and the
Bjorck et al. (1998) event stratigraphy. Both calendar
and radiocarbon ages are used in the paper, because
calibration between the two time scales for that
period is not straightforward or reliable.
335
2. DegJaciaJ climatic oscillations
Many sites in western and central Europe and
Greenland show multiple deglacial climatic oscilla­
tions. Here we select several sites from regions
around the North Atlantic Ocean (Fig. 1) to illustrate
these climatic events (Fig. 2). Before we discuss the
evidence from the interior of North America, we
briefly review well-documented records from coastal
regions (Fig. 3).
Many paleoclimatic records from the North At­
lantic region during the last deglaciation from 15,000
to about 7000 cal BP show a classic deglacial cli­
matic sequence from the initial BOA warming, to
BOA warm period with two or more minor oscilla­
tions, to the YD cold period, and to Holocene warm­
ing with PB and a cooling event at 8200 cal BP
(8.2-ka event) (Fig. 2B-E). The last Bond cycle
from the peak BOA warming at - 14,500 cal BP to
the onset of the Holocene at - 11,500 cal BP shows
a progressive cooling through two or three D-O
cycles, followed by an abrupt warming. The coldest
part of this Bond cycle is marked by the YD (Hein­
rich layer HO; Andrews et al., 1994). These events
Atlantic
Ocean
Fig. I. Map showing location of selected paleoclimatic sites around the North Atlantic Ocean: Crawford Lake in North America (Yu and
Eicher. 1998), Summit ice-cores from Greenland (Dansgaard et al., 1993; Grootes et al., 1993; Stuiver et aI., 1995), marine core Tro1l3.l
from North Atlantic (Lehman and Keigwin, 1992), Gerzensee in central Europe (Eicher, 1980), and marine core PL07-56PC from Cariaco
basin in tropical Atlantic (Hughen et aL 1996).
336
z. Yu. H.E. Wright Jr. / Earth-Science Reviews 52 (2001) 333-369
can be traced from North America (Fig. 2A) to
Greenland (Fig. 2B), the North Atlantic Ocean (Fig.
2C), central Europe (Fig. 2D), and the tropical At­
lantic Ocean (Fig. 2E). Atmospheric CH concentra­
4
tions show similar fluctuations during the major and
some minor climatic events (Fig. 2F).
records with high resolution demonstrate these
deglacial climatic oscillations in more detail (Fig. 2C
and E; Lehman and Keigwin, 1992; Hughen et aI.,
1996). Other marine records from the North Atlantic
also show these deglacial climatic events (e.g., Ko�
Karpuz and Jansen, 1992; Bond et aI., 1993).
2.1. Greenland and North Atlantic Ocean
2.2. Western and central Europe
Multiparameter records from Greenland ice cores
provide the clearest evidence of abrupt deglacial
climatic changes in many aspects (e.g., Fig. 2B and
F; Alley, 2000). One of these ice cores (GRIP) was
proposed by Bjorck et aI. (1998) as the stratotype for
an event stratigraphy (Table 1). The detailed glacio­
chemical data benefit from well preserved annual ice
layers that can be counted with confidence. The
oxygen isotopes from the ice reflect mostly changes
in air temperatures, showing the major YD climatic
reversal between the BOA warm period and the
warm Holocene (Fig. 2B; Johnsen et aI., 1992;
Grootes et aI., 1993; Dansgaard et aI., 1993; Stuiver
et aI., 1995; Stuiver and Grootes, 2000). During the
pre- and post-YD warm periods, several minor oscil­
lations are also clearly documented. Other proxies
show that the transitions of these abrupt climatic
shifts, especially the YD, occur very rapidly within a
few years to a few decades (Dansgaard et aI., 1989;
Alley et aI., 1993; Taylor et aI., 1993, 1997; Sever­
inghaus et aI., 1998; Severinghaus and Brook, 1999).
A significant change in atmospheric chemical com­
position occurred during the YD (Mayewski et aI.,
1994).
Ruddiman and Mcintyre (1981) used foraminiferal
stratigraphy of ocean cores to show that the southern
limit of the polar front shifted southward during the
YD climatic reversal. Deep-sea records traditionally
have low temporal resolution due to usually very low
sediment-accumulation rates, but many marine
The YD cooling had significant impact on Euro­
pean terrestrial and aquatic ecosystems, and the most
convincing continental evidence for the deglacial
climate events comes from western and central Eu­
rope. Initially, the YD climatic reversal was recog­
nized in glacier reconstructions and in pollen and
macrofossil records showing vegetation containing
the tundra plant Dryas octopetala in Denmark (Iver­
sen, 1954). Over the last century, abundant evidence
is available from mUltidisciplinary studies, but differ­
ent proxies may have responded differently and have
recorded different timings for the cooling (Wright,
1984; Pennington, 1986; Birks and Ammann, 2000).
After the Scandinavian Ice Sheet retreated from
the Last Glacial Maximum, it paused or readvanced
in many places, as clearly documented in southern
Sweden (Bjorck et aI., 1988; Berglund et aI., 1994).
The YD is marked in northwestern Europe by a
change to a pronounced periglacial condition, with
renewed soil erosion and mineral inwash into lakes
(Walker et aI., 1994). Alpine glaciers also responded
to the YD cooling. In Switzerland, for example, the
Egesen moraine was formed during the YD, as has
been recently confirmed by lOBe, 26AI and 36 Cl AMS
dating (Ivy-Ochs et al., 1996). Oxygen-isotope
records show detailed evidence for the multiple cli­
matic oscillations during the last deglaciation in
western and central Europe. Several sites in lowland
Switzerland show a climatic sequence of BOA
warming, BOA warm period, YD cold interval, and
Fig. 2. Correlation of paleorecords during the last deglaciation 05,000-7000 cal BP). (A) /l180 of lacustrine carbonates at Crawford Lake
(Yu et al., 1997; Yu and Eicher, 1998); (B) /l18 0 of ice-core GISP2 (Grootes et al., 1993); (C) Forams of Tro1l3.! (Lehman and Keigwin,
1992; age scale was tuned to Greenland ice-core record); (D) /l180 of lacustrine carbonates at Gerzensee (Eicher, 1980); (E) Grey scale of
core PL07-56PC (Hughen et aI., 1996; revised age scale); (F) Atmospheric CH4 concentration of ice cores GRIP (circles and thin line;
Chappellaz et aI., 1993) and GISP2 (thick line; Brook et al., 2000). Late-glacial ages for Crawford, Gerzensee and Tro1l3.1 cores were
tentatively tuned to GISP2 ice-core time scales on the basis of similar climatic oscillations, so the similarity in timing does not mean
synchrony of events at centennial scales.
z. Yu. H.E. Wright Jr./ Eanh-Science Reviews 52 (2001) 333-369
and Siegenthaler, 1976; Eicher, 1980, 1987; Siegen­
thaler and Eicher, 1986; Lotter et aI., 1992; Ammann
et aI., 2000). This sequence shows remarkable simi-
warm Holocene, with two minor oscillations in BOA
(Aegelsee Older Dryas; Gerzensee intra-Aller0d
cold period) and one (PB) in early Holocene (Eicher
=
=
9000
m­
e
Il.
11000
13000
15000
-9
-10
S>
-11
�
Age (cal yr BP)
BOA
'E
...
8.
-
337
-34
-36
-38
GISP2
(Gr�nland)
o
20
40
60
80
100
C
-40
Troll 3.1
(No�h Atlahtic)
o
-5
-6
-7
-8
Gerzensee
(Centr,al Europe)
:0.
-9
-10
220 �---+----+-----+----.J----4-----+-----l-M-� -11
200
E
o
:E
en
E
...
Q)
S:
o
co
�
PB
120 �--4----+--�---�--� 4
210
§'
EH
me
Il.
E
...
Q)
c.
-
o
co
.,..
<Q
190 "'••• N'.''''
f
C>
180
170
160 f------+---+---l--+-�-+---_+�=f.,.._- 800
(Greetlland) •
700
�
600
S:
500
:I:
()
�--�--�----� 400
7000
9000
11000
Age (cal yr BP)
13000
15000
c.
v
338
Z Yu. H.E. Wright Jr. / Earth-Science Reviews 52 (2001) 333-369
Fig. 3. Location map of paleoclimatic sites in the interior of North
America discussed in the text. Coastal regions (shaded areas) that
show evidence for deglacial climatic oscillations are not discussed
in detail in the text: (A) Greenland (e.g., Dansgaard et aI., 1993;
Grootes et aI., 1993); (B) Baffin Island and northern Labrador
(Andrews, 1994); (C) Eastern coast of North America (Mot! et aI.,
1986; Peteet et aI., 1990, 1993; Mayle et ai., I 993a,b; Cwynar and
Levesque, 1995); (D) Southern Alaskan coast (Engstrom et ai.,
1990; Peteet and Mann, 1994; Hansen and Engstrom, 1996); (E)
Pacific Northwest coast (Mathewes et aI., 1993; Mathewes, 1993;
Grigg and Whitlock, 1998) and (F) California coast (e.g., Benson
et aI., 1997). Dots show location of sites in central North America:
0-3) Crawford Lake, Twiss Marl Pond (Yu and Eicher, 1998),
and Gage Street site, southern Ontario, respectively (Fritz et ai.,
1987; Yu, 2000); (4) Lake Seneca of the Finger Lakes region,
New York (Anderson et aI., 1997); (5) Nichols Brook site, New
York (Fritz et al., 1987; Yu. 2000); (6) Pyle and Stotzel-Leis sites,
Ohio (Shane. 1987; Shane and Anderson, 1993); (7) Prince Lake,
northwestern Ontario (Saarnisto. 1974); (8) Lake Gribben forest
bed. Michigan (Lowell et ai.. 1999); (9) Deep Lake, Minnesota
(Hu et al., 1997. 1999); ( 10) Rattle Lake, northwestern Ontario
(Bjorck. 1985); (I!) Sky Pond and Black Mountain Lake, CO
(Reasoner and Jodry, 2000); (12) Inner Titcomb Lakes moraine of
the Wind River Basin, WY (Gosse et aI., 1995); ( 13) Crowfoot
moraine, Alberta (Reasoner et ai., 1994; Reasoner and Huber,
1999); ( 14) Southern High Plains (Holliday, 2000).
larity with ice-core records from Greenland
(Siegenthaler et ai., 1984; Lotter et ai., 1992). Oxy­
gen-isotope records that show deglacial climatic os-
cillations are also available from Poland (Goslar et
ai., 1993, 1995; Ralska-Jasiewiczowa et ai., 1998),
southern Germany (von Grafenstein et ai., 1992,
1994, 1998, 1999), Ireland (Ahlberg et ai., 1996),
and southern Sweden (Hammarlund et ai., 1999).
Paleobotanical records from pollen and macrofos­
sil data generally show an open vegetation during the
YD cold period. For example, the YD cooling was
marked by tundra taxa in Britain and Ireland (Hunt­
ley and Birks, 1983; Walker, 1984; Watts, 1985) or
by the expansion of Artemisia in the grassland
(Watts, 1977; Cwynar and Watts, 1989). In the
Netherlands, closed forests were replaced by either
open woodlands or dwarf shrub and heath vegetation
(Van Geel et ai., 1989; Bohncke, 1993; Hoek, 1997).
In lowland Switzerland (the Swiss Plateau), the YD
event is recorded by an increase of juniper and
pioneer heliophilous taxa in the pine-birch wood­
lands (Ammann, 1989; Ammann and Lotter, 1989;
Lotter et ai., 1992; Ammann et ai., 1994; Lotter,
1999). In western and central Europe, the YD is
clearly shown in paleobotanical records, but the mi­
nor climatic oscillations (e.g., PB, G/K, OD) are not
so obvious (but see Lotter, 1999; Birks and Am­
mann, 2000; Leroy et ai., 2000). Fossil insects from
northern Europe show clear evidence for deglacial
climatic oscillations, including the BOA warming,
declining temperature trend during the BOA warm
period, and the YD (Coope, 1977; Atkinson et ai.,
1987; Coope and Lemdahl, 1995; Coope et ai., 1998).
Other paleoclimatic proxy data also show sensitive
response to climatic oscillations, for example, chi­
ronomids (Brooks et ai., 1997; Mayle et ai., 1999),
land snails (Rousseau et ai., 1998), and lake levels
(Magny and Ruffaldi, 1995). Isarin and Bohncke
(1999) mapped the inferred July temperatures of
northern and central Europe during the YD interval
on the basis of climatic indicator species (e.g., cer­
tain aquatic plants) (see also Isarin and Renssen,
1999).
2.3. Eastern coast of North America
Mott et ai. (1986) summarized the geologic and
palynologic results from Maritime Canada that
showed clear evidence of cooling between about
11,000 and 10,000 14C BP. That paper gained
widespread acceptance as evidence for the YD on
z. Yu, H.E. Wright Jr./ Earth-Science Reviews 52 (200]) 333-369
the other side of the Atlantic Ocean. In southern
New Brunswick and central mainland Nova Scotia,
the YD is indicated by a succession from
woodland/forest to tundra (Mayle et al., I 993a,b;
Cwynar et aI., 1994; Levesque et al., 1994; Mayle
and Cwynar, 1995), but in central New Brunswick
and northern Nova Scotia from shrub tundra to herb
tundra (Levesque et aI., 1993; Mayle et aI., 1993a,b;
Mott, 1994). Relatively low organic matter (as mea­
sured by loss on ignition) indicates renewed solifluc­
tion, increased minerogenic inwash, or reduced lake
productivity due to cooling (e.g., Mott et aI., 1986;
Mayle et aI., 1993a; Mott and Stea, 1993). Chirono­
mids have been successfully used to reconstruct
summer surface-water temperatures for the YD and
G/K events in Maritime Canada and Maine (Walker
et al., 1991; Wilson et aI., 1993; Levesque et aI.,
1993, 1994; Cwynar and Levesque, 1995). Anderson
and MacPherson (1994) summarized palynologic data
from Newfoundland and showed an increase in herb
tundra taxa and in sediment alkali during the YD,
suggesting reduced vegetation cover and accelerated
soil erosion. They also reported evidence for minor
climatic oscillations shortly before the YD and in the
early Holocene. Miller (1997) analysed fossil insects
from three late-glacial sites in Nova Scotia and
found evidence for the YD, but it is not as strong as
the palynologic and lithologic records.
In southern Quebec, slight changes in pollen as­
semblages within herb tundra and decreased pollen
concentration suggest the YD climatic reversal
(Marcoux and Richard, 1995) as well as an early-Ho­
locene cold event at 9500 14C BP (Richard et aI.,
1992; Richard, 1994). In southern New England, the
YD is recorded by a decrease in the pollen percent­
age of thermophilous temperate deciduous trees such
as Quercus and Fraxinus and increase of boreal
forest taxa such as Abies, Larix, Picea, Betula, and
Alnus (e.g., Peteet, 1987; Peteet et aI., 1990, 1993,
1994; Maenza-Gmelch, 1997a,b). In Baffin Island
and northern Labrador, Andrews (1994) reviewed
terrestrial and marine evidence and showed that a
permanent ice cover (sea ice or an ice shelf) existed
during the YD interval. Lowe (1994) and Lowe et ai.
(1995) summarized evidence for climatic oscillations
during the last deglaciation around the North At­
lantic Seaboard, including the east coast of North
America (Fig. 4).
Southem
New England
Nova
Scotia
339
�:rSWjCk
Ne wfoundland
Quebec
9r-��----�----'---����
iL 10
<Xl
" Younger
c, Dryas
:;;
Q)
>c
0
-e
11
'"
"
0
'6
t'!
g
12
o
�
� 13
Schematic
,
1L-1,o
Mean July
14 Temperature
rC)
�o
i
201
-------.." .
Schemabc
ummer walr
emperature-r
('C)
!
II
I
10 15
'---'
Mean July
Temperature
rC)
Fig. 4. Summary paleotemperature curves during the last deglacia­
tion for the regions in east coast of North America (modified from
Lowe and NASP Members, 1995).
2.4. West coast of North America
On Pleasant Island in the Glacier Bay area of
southeastern Alaska, Engstrom et ai. ( I 990) and
Hansen and Engstrom (1996) described a pollen
sequence implying that an established lodgepole pine
(Pinus contorta) parkland or forest reverted to shrub­
and herb-dominated tundra (Ericaceae, Poaceae,
Cyperaceae, and Artemisia) from 10,800 to 9800
14C BP. This vegetational change is matched by
geochemical evidence of reduction of organic matter
from catchment soils and increased mineral erosion
(Engstrom et al., 1990). They interpreted these vege­
tational and geochemical changes as caused by a
possible YD cooling event, because no known read­
vance of glaciers at that time in the area could
explain the changes. On Kodiak Island in southwest­
ern Alaska, Peteet and Mann (I 994) found distinct
lithologic oscillations and a dramatic reversal in
vegetation involving the near disappearance of Poly­
podiaceae ("Fern Gap") from 10,800 to 10,000 14C
BP, suggesting colder and drier conditions. They
interpreted this reversal as a high-latitude Pacific
expression of the YD event.
Just as with the YD event around the North
Atlantic, evidence for the climatic reversal in the
Pacific Northwest is best expressed in hypermaritime
and maritime climatic regions (Mathewes, 1993).
The most notable evidence for the YD is the pollen
peaks of mountain hemlock (Tsuga mertensiana), an
340
z. Yu, H.E. Wright Jr./ Earth-Science Reviews 52 (200]) 333-369
indicator of cool and moist climate, in western
Washington (Heusser, 1973, 1977), along the British
Columbia coast (Mathewes, 1973), on Queen Char­
lotte Island (Mathewes et al., 1993), and on Vancou­
ver Island (Hebda, 1983). At two sites in western
Oregon, Grigg and Whitlock (1998) found an in­
crease in pollen of western white pine (P. monticola)
between 12,400 and 11,000 cal BP, indicating cooler
winters and drier summers than in earlier periods,
and they suggested that this Pinus expansion may
correlate with the YD climatic reversal. They sug­
gested that the weak expression of the YD event was
due to the relative inland location of their study sites.
Farther south in the Great Basin of California, Ben­
son et al. (1997) reconstructed the hydrological bal­
ance of Owens Lake from carbonate 8180 values and
found that millennial and century-scale dry events in
western North America during the last deglaciation
occurred at about the same time as cold events
recorded in Greenland ice, including the YD and
pre-YD oscillations.
2.5. Other places in the world
Several recent reviews have been published that
summarize the state of knowledge about evidence for
deglacial climatic oscillations, especially the major
YD climatic reversal (Rind et aI., 1986; Wright,
1989; Peteet, 1995; Rutter et aI., 2000). Increasing
evidence is available for South America from paly­
nologic data (Kuhry et aI., 1993; Van der Hammen
and Hooghiemstra, 1995; Isbele et aI., 1995; Leyden,
1995; Hansen, 1995) and the glacier record (Osborn
et aI., 1995). In New Zealand, Denton and Hendy
(1994) correlated a glacial advance of the Franz
Josef Glacier with the YD cooling. Southern Hemi­
sphere ice cores also suggested climatic oscillations
during the last deglaciation (Thompson et aI., 1995).
An et al. (1993) suggested that a strengthened sum­
mer monsoon indicated by loess data from central
China was correlated with the YD event. Zhou et al.
(1996) suggested that significant and rapid oscilla­
tion of paleomonsoon proxy for monsoonal eastern
Asia occurred during the YD interval. Porter and An
(1995) suggested that climatic events in China corre­
lated with the North Atlantic region during the last
deglaciation. In the varved sediments of Lake Van in
eastern Turkey, the YD is well represented in the
sediment chemistry and the pollen profiles by indica­
tions of a cold dry climate (Lemcke and Sturm,
1996). In east Africa, a lower lake level was corre­
lated with the YD interval (Roberts et ai., 1993), as
in other lakes in the tropics (Street-Perrott and Per­
rott, 1990).
The Antarctic Cold Reversal (ACR) from the
Byrd and Vostock ice cores in Antarctica appeared
to precede the YD from Greenland ice cores by at
least 1000 years, as indicated by synchronization of
records with the isotopic ratio of molecular oxygen
(Bender et aI., 1994; Sowers and Bender, 1995) and
with the global atmospheric concentrations of
methane (Blunier et al., 1997). Similar phase rela­
tionship also existed earlier during the last deglacia­
tion, showing that Greenland warming associated
with D-O events lags the similar events in Antarctica
by a couple of thousand years (Blunier et aI., 1998).
These data suggest that these climate changes origi­
nated in the Southern Hemisphere and that they
spread to the north. However, isotopic climate proxy
record from Taylor Dome ice core in coastal East
Antarctica shows synchronous climatic changes with
Greenland during the YD (Steig et aI., 1998). High­
resolution records of isotopic and methane data from
Greenland ice cores indicate that the warmings in the
North Atlantic during the last deglaciation occurred
several decades before the tropical warmings
(Severinghaus et aI., 1998; Severinghaus and Brook,
1999). Understanding how the Northern and South­
ern Hemispheres are coupled during climatic events
is a central issue in climate dynamics (Blunier et aI.,
1998; White and Steig, 1998). It appears that many
questions remain to be answered.
3. Evidence from the Great Lakes region
3.1. Stable isotopes
Clear evidence for deglacial climatic oscillations
in the Great Lakes region have been recently docu­
mented by stable-isotope records at two small lakes
along the Niagara Escarpment in southern Ontario
(sites 1 and 2 in Fig. 3; Yu and Eicher, 1998). The
oxygen-isotope records from three cores at Crawford
Lake (Figs. 5 and 6) show the classic European
climatic sequence. A striking feature from all three
Z Yu. HE. \Vri.�h! Jr.
III
l:
III
(l)
> 06 ill
l:
(l)
ill 0
(l)
...... O)N
(\l « l:
E .c ill
......
.---.
.-
E
�
.c
-0..
ill
0
340
DC
E
0
--
.c
0..
ill
0
450
.-
E
0
BC
--
SC
.-
.-
0
0..
<::,§
I PB
460
-
350
10,000 14C BP
(Picea-Pinus
transition)
:...
(1)
tnt/)
c:
::l
470
�
>.
�O
-
360
10,920 14C BP
(AMS date from
I
Twiss Pond)
G/K
480
12,000 14C BP
(Tundra-Picea
490
Fig.
5.
Photographs and correlation of scdiment scctions of cores
transition)
DC
Osc·jllation: G/K. Gerzcnscc or Killarney Oscillation (modified hom Yu. 1997).
cores is the
0 minimum in the upper Picea­
dominated pollen zone, which indicates a decline in
temperature. These negative shifts of 01'0 of 0.5'Xc.
-13,000 14C BP
SC and BC from Crawford Lake. southern Ontario. PB. Prehoreal
1.5':7rc• and 1.2O/C( for cores DC, SC, and BC, respec­
tively. con-espond \vith the beginning of the YD cold
event at - 11.000 I�C BP (Yu and Eicher. 1998).
z. Yu, H.E. Wright Jr. /Earth-Science Reviews 52 (200]) 333-369
342
iL
iL
co
co
�"E
�
��
�(j)
Q)-
Greenland Summit
GISP2 Core
010
<C ,
7504
8000
Crawford Lake
- - _
8200 cal BP_=�:...
cooling event
9000
SC B<;:
i
�-
:?�
<:.o
ro
gJ, U
<C
'
6500
':---H 5 7000
8000
10,000
9000
11,000
'"
'" �
a: �
10,000
12,000
11,000
13,000
B011ing
Aller0d
OD
14,000
-42
-41
-40 -3 9 -38 -37
8"0 %0 (V-SMOW)
-36
-35
12,000
-11
-10 -9
-8
8'.0 %0 (V-PDB)
Fig. 6. Event correlation of 8180 profiles from carbonates at Crawford Lake (core SC: heavy curve; core BC: dashed curve) in the Great
Lakes region and from Greenland ice-core GISP2 (left bar-curve) on 14C and calendar-year time scales, respectively (Grootes et aI., 1993;
Yu and Eicher, 1998). At Crawford Lake, the sequence of climatic oscillations includes the BOA warming, G/K. YD, PB and HE-S
[Holocene Event 5; Bond et al., 1997; i.e., the 8200 cal BP cooling event], and possibly OD (Older Dryas). All these oscillations recorded at
Crawford Lake have about a third to half the amplitude of the Greenland record, and PB and HE-S have half the amplitude of the YD and
G/K/IACP at both locations (modified from Yu and Eicher, 1998).
After this minimum, the 8180 values show an abrupt
positive shift of
3%0
for cores DC,
Holocene warming linked with the
Picea-Pinus
1.2%0, 1.5%0,
and
SC, and BC, respectively, indicating the onset of
transition at
10,000
14C BP, In the early Holocene, a
minor negative 8180 excursion of
-
0.5%0
at
9650
14C BP occurs in the three cores, corresponding to
the PB event. The
8200
cal BP cooling event is
evident from two shallow cores (SC and BC). During
the BOA warm period, a negative excursion of 8180
shortly before the YD at core SC indicates a cold
interval correlative with the intra-Alleni)d cold period
(IACP) in Greenland (Lehman and Keigwin,
1992),
Gerzensee Oscillation (G) in central Europe (Eicher,
1980),
and Killarney Oscillation (K) in Atlantic
Canada (Levesque et al.,
1993).
This climatic se­
quence is remarkably similar to records from around
the North Atlantic (Eicher
Johnsen et
1980; Lotter et al., 1992;
al., 1992; Levesque et al., 1993; Dans-
gaard et al.,
1996;
1993;
Alley et al.,
Stuiver et al.,
1995;
Bjorck et al.,
1997).
At Twiss Marl Pond, oxygen-isotope 0;180) re­
sults from mollusc shells, Chara-encrustations, and
bulk carbonates also show a classic climatic se­
quence of a warm BOA at
BP,
a cold YD at
Holocene warming at
9650
- 12,500-10,920 14C
10,920-10,000 14C BP, the
10,000 14C BP, a brief PB at
14C BP, and a possibly IACP event shortly
before
11,000 14C BP (Yu and Eicher, 1998; Yu,
2000). The 8180 records show a negative shift of
1.3%0 at 10,920 14C BP (at 490 cm) and a positive
shift of up to 2%0 around - 10,000 14C BP (at 390
cm) (Fig. 7A). The more negative intervening inter­
val indicates a cold period corresponding with the
YD event. During the YD interval, 8180 fluctuated
and had minimum values at first and slight increase
in the second half, similar to the bipartition indicated
in Europe by sensitive plant fossils (Isarin and
Carbonate Oxygen Isotope Profiles from the Great Lakes Region
Bohncke. I
shift in
of the Holocene. a minor
excursion of
OA'j{( at 9600
BP
3150 cm) correlates \v11h the PB cvent This minor
oscillation was also indicated
recunence of Picea
at Twiss Marl Pond (Yu.
and more
clearly at nearby Cra\vford Lake (Fig. 15; Yu and
Eicher. 19(15). Before the YD intervaL another slight
negative excursion of
0 at 500-510 cm was
recorded in mollusc shells and bulk marl.
correlated with the lACP /G /K events. for it was
indicated
of Al and K (Yu and Eicher.
19(15)
In the eastern Great Lakes
several other
studies have examined climatic and vegetational
during the last
transition. Multiproxy data from several small lakes, however. failed to show evidenee for
climatic
at the onset
oscillations and even climatic
Yu (2000)
of the Holoeene (Fritz et aL
provided an alternative interpretation of stable-iso­
tope records from the
Street and Nichols Brook
-
the
3 in
shows fluctuations in the
Holocene. A
excursion of
J .2(;;, occurs
in marl
in the upper Picea zone.
(Fig.
hut also in Va/raw fricarif1aw shell samples (Fritz et ai., 1(157), The modified
based on the major Picca--Pinlls transition and the
herb-Piu'{/ transition (Yu, 20(0), shifts this
excursion of 8"0 (at 400-360 em) close to the Yi)
interval. The depletion trend of
during (hat
interval is also similar to the Twi"s and Crawford
:
records (Jiu and Eicher. 1(91); Yu, 1907.20(0).
8
In
excursion in
to the reCUlTence or
of Pia'o pollen at the Gage Street site
(Fritz et aL. I
which may correlate with the PB
at 9650 BP as demonstrated at Twiss J\hrl Pond and
Crawford Lake.
At the Nichols Brook site in northwestern New
York (site 5 in Fig. 3). on the basis of lithology,
pollen, fossil insects. and detailed stable-isotope
-
HE
Crawford Lake Summary
Q
Ij)
'- ill
ec:
.cO
uN
Holocene
(Preboreal)
Younger
Dryas
----_ .
I:L
co
�
m
ill
�
"0
'"
!!!
!J
it
Vegetation
Events
9000
��
(l) .=
g§
PB - ro
f?
10000
Pmus
forest
5
Younger
Dryas
11000
m-g
G/K t:
Picea
woodland
5;::
<(l)
00.
12000
13000
Fig.
Inferred
Ciimate
co
�_
�______L_
._ .• __
�
_•____
Tundra
Deglaciation
S. Compo,;ite summary diagram for Crawford Lake (modified from Yu. 1'1'11 L Chronuzones follow rvlangcrud c! al. (l'i7·0. PB.
Preboreal O,;,:illation: YO, Younger Dryas: G/K. Gerzen,;cc or Killame\, O,;cillations.
records from mollusc shells, Clwru-encrustations,
and hulk carbonates. Fritz et al. (J 987) concluded
that there was no evidence for late-glacial climatic
oscillations. However. oxygen isotopes do shO\v sev­
1'
eral shifts, The 0 0 values from Va/nata tricarillata
shells show a negative shift of - 1'7; (from
9,3o/r,
(at 3] 0-270 cm) to
10.3'7;( (at 240-170 cm), and
a positive shift of - lo/r, at 170 cm (Fig. 7C: Fritz et
aL 1987), The revised chronology, based on rejec­
I+
tion of C dates from the flowing-water interval as
suggested by fossil insects, would place the negative
Oil' 0 shift at 250 cm at about 11,600 BP and the
positive shift at 170 cm at 10.200 BP, With the
revised chronology, the negative excursion of - lo/r(
1;;
in <') 0 at 250-170 cm appears to cOlTespond with
the YD event. The PB event was also
at
this site hy a recurrence of Picl:'(J pollen (Fritz et al..
IK
1987) and a slight negative excursion of <') O from
mollusc shells at 150 cm (9600 BP')).
Two coring sites from Lake Erie documented
1"
major shifts in 0 0
et aL 1975; Lewis and
Anderson, 1992), which were initially interpreted as
representing temperature changes (Fritz et aL 1975)
and later as caused hy changes in meltwater dynam­
ics of the Great Lakes (Flitz. 1983: Fritz et aI., 1987:
Lewis and Anderson. 1992; also see Rea et aL
site 13 j 94. two
increases
1'
BP and 10,000 BP in 0 0
from mollusc and ostracode shells (Fritz et a1., 1(75)
were caused hy a reduction in
meltwater in
the Great Lakes drainage system (Fritz, 1983: Fritz
et aL. 1987). During deglaciation, the Great Lakes
received
quantities of meltwater (Rea et al..
I 994a.b). Consequently,
in water budget
in these isomay have complicated climatic
topic records. Such meltwater complications may
also apply to the isotopic record at the Long Point
site in the Lake Erie basin (Lewis and Anderson.
III
1992), which also shows a large increase ( 1"
0 0 at - 10.000 BP, and for j!es from Lake Huron
and Georgian Bay (Rea et aI., 1 994a, b). In fact.
these authors interpret their
records as caused
meltwater dynamics and lake-level history, rather
than climatic change directly.
At Deep Lake. southeast of proglacial Lake
siz in northwestern Minnesota (site 9 in
3), Hu
et al. (1997, 1
found two
excursions in
oxygen isotopes from hulk carbonates
2050S-;: carbonates) during the early Holocene. A 3'k,
decrease in 81'0 from I L200 to 10,200 cal BP was
interpreted as a result of decreased summer temperature caused
the nearby presence of Lake
��
z. Yu, HE Wright Jr. / Earth-Science Reviews 52 (2001) 333-369
(Hu et al.,
1997),
3.2. Vegetation
records
but the lack of pollen and vegeta­
tion response to this lake-induced cooling indicates
that it was insufficient to modify the surrounding
vegetation. A second decrease of
-
2%0
in
Sl80
345
evidence from
paleoecological
At Rattle Lake in northwestern Ontario (site
10 in
(1985) found a pollen se­
quence from a Picea/ Fraxinus/ Ulmus/Artemisia
(warm) to a Picea/ Salix / Cyperaceae zone at
11,1000-10,200 14C BP (cold) to a Picea/Pinus/
Juniperus/Betula zone (warm). The near disappear­
ance of Fraxinus and Ulmus at 11,1000 -10,200 14C
8300 cal BP, suggesting a
climatic cooling (Hu et aI., 1999).
Anderson et aI. (1997) suggested that a 1%0 de­
crease in SI80 at 10,100-8200 14C BP (
11,7009200 cal BP) at Seneca Lake in the Fingers Lakes
region of New York (site 4 in Fig. 3) was caused by
Fig.
influx of meltwater into the Great Lakes that reduced
by very low pollen-accumulation rates characterized
occurred from
8900
to
-
summer temperatures. They correlated this excursion
9),
Bjorck
by a dwarf-shrub tundra. Wright
(1989)
suggested
that this climatic reversal is correlative with the YD
with the PB at
9600 14C BP in Greenland ice cores
(Johnsen et al., 1992). However, the PB event only
lasted for about 200 years (e.g., Bjorck et al., 1996),
event.
In the southern Great Lakes region (western Ohio,
Indiana, and Illinois), pollen diagrams reveal a dis­
whereas Anderson et al.' s isotope excursion lasted
2000
Fig.
BP suggests a cold climate, which is also supported
a cooling event following the YD, as a result of
for about
3;
tinct reversal in the pollen sequence for an interval
radiocarbon years. This significant
correlative with the YD (Shane,
difference in duration for a presumed same climatic
event suggests the importance of local factors in
1989;
bonates.
10),
Shane and Anderson,
1980, 1987; Wright,
1993). Most clearly at
the Pyle and Stotzel-Leis sites on the Till Plains (Fig.
controlling stable-isotope composition of lake car­
after a long dominant period
Picea pollen de-
Rattle Lake, Ontario
E
�
.t::
0..
<1l
Cl
1100
E
1200
8420 "" 10.150-10.850 .... :
11.110""
�
____
Cold
E
1300
�
1380
% 0
0
0
30 0
30 0
0
0
0
30
60 0
0
Pollen percentages
Fig. 9. Summary pollen diagram from Rattle Lake, northwestern Ontario that shows vegetation response (decline of Fraxinus and Ulmus) to
the Younger Dryas cooling (Bjorck, 1985; Wright, 1989).
z. Yu, H.E. Wright Jr. / Eanh-Science Reviews 52(2001) 333-369
346
PYLE
,"(; doles
(yt BPI
S I TE
r---------------TREES ----
�/
Eo.
v"
ap
o �\�
IOO.J
-:
9000
10,000
1 1,000
12.000
.13.000
-13,510
14.000
• ..---...,
h h 1M-
STOTZEl - LEIS
- 5830
SITE
6000
7000
8000
9000
- �gg
8570
9760
10,000
-10.260
-10,330
- 11 ,3:50
12,000
13,000
-13,070
14 ,000
15.000
"'24, 110
Fig. 10. Summary pollen diagrams from Pyle and Stotzel-Leis sites in the southern Great Lakes region that show clear vegetation response
(Picea recurrence) to the Younger Dryas cooling (reprinted from Shane (1987) by permission of Taylor & Francis).
creased to about 5% at
pollen of
13,000-11,000 14C BP as
Fraxinus, Quercus, OstryajCarpinus, and
other temperate hardwood trees dominated the pollen
assemblage.
Lawrence River and identified five types of pollen
anomalies from the normal pollen sequence during
the early Holocene (Fig.
11).
They interpreted that
these pollen anomalies were results of localized cold
Picea then abruptly increased to 30%,
and other boreal conifers ( Abies and Larix) also
climate caused by enhanced meltwater discharge from
abruptly decreased with the arrival of
ported that the strongest vegetation response to melt­
increased. These conifer pollen percentages then
Pinus. The
Picea recurrence after an interval with relatively
abundant Fraxinus and OstryajCarpinus pollen
lasted from about 11,000 to 10,000 14C BP (Shane,
1987; Shane and Anderson, 1993).
Anderson and Lewis (I992) summarized pollen
records around the Great Lakes and along the St.
proglacial lakes at
10,000-8000
14C BP. They re­
water-induced cooling occurred at sites within or
along margins of large water bodies.
At Crawford Lake and Twiss Marl Pond, the YD
climatic reversal was documented by a negative ex­
cursion in <'l180 and a change in lithology and ele­
mental geochemistry (Figs.
6-8). However,
this event
Z. YII. H.E. Wright Jr. / Earth-Science Reviews 52 (2001) 333-369
AGASSIZ BASIN
I
347
GULF OF ST. LAWRENCE
ka
HERB
* ONSET DEFINED
HERB
* TERMlNIQ'ION DEFINED
Fig. II. Correlation of cold-tolerant pollen assemblages (stippled bands) along the Great Lakes-SI. Lawrence regions (from Anderson and
Lewis, 1992). Time scale is in radiocarbon year BP (ka 1000 year I·C BP).
=
occurred in the upper part of the spruce (Picea)
zone. There was no significant forest response to the
YD cooling. This was probably a result of the insen­
sitivity of non-ecotonal vegetation. In the eastern
Great Lakes region, the Picea dominance started as
early as over 1 2,000 14C BP (Jacobson et al., 1987).
In the following '" 2000 years, the Picea belt may
have moved latitudinally in response to climatic
changes. However, as Crawford Lake and Twiss
Marl Pond were situated in the middle of the broad
spruce belt at 1 1 ,000 14C BP, there was no detectable
change in forest composition recorded by pollen. A
forest response has been detected in the northern and
southern boundaries of the spruce belt at the YD
time, e.g., in Ohio and Indiana (Shane, 1 987) and
northwestern Ontario (Bjorck, 1985). This implies
either that elsewhere pollen techniques are not sensi­
tive enough to detect subtle forest change or that the
forest persisted below its threshold in non-ecotonal
locations (Shane, 1987). Nevertheless, the vegetation
change was shown by the slight increase or persis­
tence of herbs and decrease of pollen concentrations,
although it was not as significant as isotopic and
lithologic records. The brief climatic oscillation at
9650 14C BP caused the recurrence of Picea pollen,
because at that time the Picea-Pinus ecotone was
near the sites.
Mayle et ai. (1 993b) summarized the pollen evi­
dence for the YD event in eastern North America
and proposed the peak or persistence of alder ( Al­
nus) pollen as an indicator. However, this is clearly
not the case for sites in the Great Lakes region.
3.3. Lake levels, meltwater and climate
Lake levels in the Great Lakes have been recon­
structed and continuously refined over the last
decade, and their connection with meltwater dis­
charge and with climatic oscillations has been dis­
cussed on the basis of pollen and stable-isotope data
(Fig. 1 2; Lewis and Anderson, 1989, 1992; Ander­
son and Lewis, 1992; Rea et aI., 1994a,b; Lewis et
al., 1994). Rea et ai. (I994b) suggested that the YD
cold event was coeval with the Lake Algonquin
highstand at 1 1 ,200- 1 0,200 1 4C BP and was caused
by the lake effect as proposed by Lewis and Ander­
son (I 992). On the basis of isotopic and lake-level
data from Lake Huron and Georgian Bay, Rea et ai.
(1 994a,b) found that the highstands, including Lake
Algonquin, were characterized by isotopically heavy
water. In contrast, the intervening lowstands were
characterised by cold, dilute, isotopically very light
water, as indicated by their isotope and ostracode
data (Rea et aI., 1994b). Lewis et ai. (1 994) com-
(2{){J l J
w
g
(/J
w
>
Q)
.J
1
,-.
o
o
"­
o
Q)
.:.::
CO
.J
c:
·w
ttl
CO
c:
e
o
co
:::l
::r:
7
8
Ii
F i !! . 1 2. Huron Basin during the last deglaciation. Lake
data from Ulrc, in Lakes Huron
higlbtanti.
D7P. 'Y1 17).
kvtl, and oxy!!en
( Sl V ) and Gcorgi�n
Michigan
hined seismic. l ithostratigraphic, and biotic data to
reconstruct the l ake-level history of the northern
Huron Basin.
suggest a steady drop in lake
from
levels from the main Algonquin
to l O . OOO
BP. Lewis et aL ' s (1994 )
lake-level history (Fig. 10 in their paper: see also
2 in M oore et al., 20(0) is slightly d ifferent in
from Rea et £11. ' s ( 1 994a:
I
3.4. !',,1o railles {tlld oscillations
the ice sheet
11
10
Radiocarbon Age (ka)
rh(' southern
mil/'-
During the last deglaciation. there were repeated
oscillations ( advance and retreat) of the south­
ern margin of the Laurentide Ice Sheet in the Great
Lakes
which l eft complex moraines. If
moraines occurred over a
geographic area, they
not be caused simply
ice-sheet dynamics
local or regional climatic iluctuations. Saar­
nisto ( 1 974 ) recognized a series of end moraines in
the Lake Superior region of Ontario ( site 7 i n
3)
and Michigan that were formed between 1 1 ,000 and
1 (), 1 00
BP, These moraines i ndicate slowdmvn
" .� .' m, Hn"JH during that time, preceded
rapid ice retreat This
called
StadiaL a reversal in the
con-elated with the Y D event
c ial climatic
( Saarni sto. 1974) . The lack of polien evidence for
the cli matic reversal i n this region was attributed to
from Mome
Bay
OP).
12
et at
( 1 '1(4) and Rea el
aL
( 1 9'14a).
Isotope
mS. main Stanky lowstand. c1vL carlv Manawa
non-ecolonal vegetation, because spruce forest /
woodland had already occupied most of the available
l andscape at that time, and to
of
techniques in
c l imatic changes of thi s magnitude ( Saarnisto, 1 974).
LO\vell et a1. ( 1 999) confirmed the age (l0,025
!.iC BP) of the Lake Gribben forest bed south of
Lake Superior in Upper Michigan (site 8 i n
3)
dating nine wood samples. and they argued that
the ice advance (Marquette readvance) that buried
ice-contact fan was the
the forest by a
result of the YD cooling event. They identified a
contemporaneous glacial margin that extended al­
most 1000 km from Duluth. MN. to North
Ontario, and argued that a surging glacier system
would not produce a l inear moraine system across
both a major basin (Lake Superior) and a major
upland (Abitibi Upland), Lowell et a1. (1999) also
reviewed the results of the last several decades of
of the Great Lakes
research on the glacial
connection with the broad-scale
and their
YD cooling event
35 Fossil beetles
Fossi l insects at several sites in the Great Lakes
region indicate a stable c l imatic condi tion without a
amelioration at the onset of the Holocene
(from 1 1.000 to 9000
BP: Miller and
z. Yu. H.E. Wright Jr. / Eanh-Science Reviews 52 (2001) 333-369
1 982; Schwert et aI., 1 985; Morgan, 1987, 1992). In
a recent synthesis and analysis of mutual climatic
ranges of 40 fossil beetle assemblages from 24 sites
in northeastern North America, Elias et al. (1996)
concluded that "our results show fewer changes dur­
ing the Late-glacial, with almost a plateau of summer
temperatures from 1 3 to 10 ka" (p. 420). An ex­
panded analysis of insect fossils for eastern and
central North America shows no indication of the
YD cooling (Elias, 1 997).
In Europe, fossil insects are regarded as one of
the most sensitive proxy indicators of late-glacial
climatic oscillations, showing clear evidence for the
YD cooling event in Britain (Coope, 1977). In Mar­
itime Canada, Miller (1997) analyzed fossil insects
from three late-glacial sites in Nova Scotia and
found that evidence for the YD is not as strong as
that presented by palynologic and lithologic studies
(Mott et al., 1 986; Mayle et al., 1 993a; Mott, 1 994).
He interpreted this weak response of beetles to the
YD cooling as caused by delayed response to cli­
matic change, by response to climate indirectly
through changes in vegetation and ground cover, and
by probably the wide temperature and habitat toler­
ances of most beetle species. He suggested a gradient
of decreasing beetle sensitivity to YD climate cool­
ing from Europe through Maritime Canada to the
Great Lakes region.
4. Evidence from the Rocky Mountains of North
America
4.1. Advance of alpine glaciers
During the last deglaciation after the full-glacial
advance of the Cordilleran Ice Sheet, alpine glaciers
readvanced and left numerous moraines (Luckman
and Osborn, 1 979; Davis, 1 988; Osborn et al., 1 995;
Osborn and Gerloff, 1 997; Clark and Gillespie, 1997).
The dating and correlation exercises in recent years
have accumulated evidence either for or against the
YD climatic reversal in the Rocky Mountains. Rea­
soner et al. (1994) fIrst convincingly established the
age of the Crowfoot Advance in the Banff National
Park, Alberta, between 1 1 ,330 and 1 0,070 1 4C BP by
AMS dating of terrestrial macrofossils from down­
stream glaciolacustrine records. They cored two lakes
349
adjacent to the Crowfoot moraine type locality and
dated the sediments bracketing an inorganic sedi­
ment interval. These inorganic sediments were asso­
ciated with the Crowfoot Advance on the basis of
bulk geochemistry and clast lithology. The Crowfoot
Advance is the best glacier evidence for the YD
climatic reversal in the Canadian Rockies (Osborn et
aI., 1995; Reasoner and Huber, 1999; Rutter et aI.,
2000).
Osborn and Gerloff (1997) reviewed the glacier
evidence from the northern Rockies, presented new
data on moraines in northwestern Montana thought
to be Crowfoot equivalent, and suggested a YD age
for these deposits. Gosse et al. (1 995) dated the Inner
Titcomb Lakes moraine in the Wind River Moun­
tains, WY, by AMS lO Be measurements of boulder
surfaces on the moraine from 1 3,000 to 1 1 ,400 lO Be
BP (equivalent to calendar years) overlapping the
YD event. Farther south in the Colorado Front Range,
Menounos and Reasoner (1997) AMS-dated an inter­
val of clastic lake sediments that show characteristics
consistent with glacier activity and suggested that
advances of alpine glaciers (Satanta Peak Advances)
occurred between 1 3,200 and 1 1 , 100 cal BP
(1 1 ,070-9970 1 4C BP). The equilibrium-line-altitude
(ELA) depression associated with these glacial de­
posits indicated that the glacier response to the YD
cooling in the Rocky Mountains was minor, similar
in extent to that of the Little Ice Age advance. The
interpretation of some glaciolacustrine records is
controversial. For the Crowfoot Advance, Leonard
(1998) argued that the correlation between lake-sedi­
ment cores and moraines as suggested by Reasoner
et al. (1994) may not be secure and suggested that
the type Crowfoot moraine predates the YD interval.
Similar controversy exists for glacier advance
along the west coast of North America. Clark and
Gillespie (1997) found that the Recess Peak moraines
in the Sierra Nevada, CA, were deposited before
1 1, 1 90 14C BP, predating the YD. In another case at
Mount Rainier, WA, Heine (1 998) found that alpine
glaciers retreated during the YD interval, probably
due to a lack of available moisture, and suggested
that the climate might also have been cold. These
authors suggested either regional variable responses
of local climate in North America during the YD
interval or differential responses of alpine glaciers to
the same climatic event.
�
b
"..V'f
/
�
Cp\0
..J
m
�
c:
=
0
::E
oX:
U
o!
g_
8480 ± 80 .
8910 ± 50
9370 ± 110
,­
9870 ± 50 ...
9910 ± 70 .......
9930 ± 60
10 120 ± 50·
10 350 ± 50.
10 420 :1: 50.
10 840 ± 50.
Pollen
AccumulatIon Rate.
�#.
�
� �
�"<I�
�
�
o
�
o�
.v
�
.
C;
�,,-s
o.�0
1:::0::
Li:::=:=----
�,f §O... � .� \�-s
".v v" <:l�
�
{8890 ± 70 .
Q)
oX:
to
.5
-:....��
�
w
v.
o
etIfJ
"v--
10
N
�
{
11 430 ± 70 .
{11
640 ± 50
;:t:
t'l'l
12
�
i
�
13
""
�
::t
CO
2000 4000
1 00
300
grains em '. yr
7770 ± 190.
.
500
1 500
100
note scale Changes
%
exaggeration xl 0
0.1 0.2
0.8
total sum of squares
0
0..
�
(J)
v.
'"
�::::
�
�
I
12
11 070 ± 50· 1 3
12 040 :1: 60 ·
�
'"
�
9970 ± 80 .
10 410 :1: 90 * ·
R
ii;'
8240 ± 70*·
"C
c:
f
14
J
rI;j �
�
2000 4000
1 00
grains em·'. yr·'
note scale changes
%
0.1 0.2 . 1.2
exaggeration x l 0
� ��!�i���rbon) IIJ dayey -siit IIlaminated silty -ciay gg silty -clay �diamict �dasts
total sum of squares
z. Yu, H.E. Wright Jr. / Eanh-Science Reviews 52 (2001) 333-369
4.2. Response of timberline vegetation
Reasoner and Jodry (2000) recently presented
pollen records from two high-altitude lakes (Black
Mountain Lake and Sky Pond) in the Colorado Rocky
Mountains showing clear and rapid response of alpine
timberline vegetation to the YD climate cooling (Fig.
1 3). Their records show declines in arboreal pollen
percentages (Picea, Abies, Pinus, and Quercus) and
pollen-accumulation rates during the YD interval,
reflecting a downslope displacement of the alpine
timberline ecotone of 60- 1 00 m in elevation. These
vegetation responses further strengthen the case of
the YD in the Rocky Mountains as documented by
glacier and glaciolacustrine records. Reasoner (1998)
compared the difference in vegetation responses to
the YD cooling between the Canadian and American
Rockies. He suggested that the lack of pollen evi­
dence for a BOA warm interval in the Canadian
Rockies was due to the short time gap between
deglaciation of the trunk valley and the YD advance
of alpine glaciers, which left little time for the
expansion of arboreal taxa prior to the YD interval.
5. Southern interior North America
In the unglaciated regions of central North Amer­
ica south of the Great Lakes and east of the Rocky
Mountains, reconstructing late-glacial paleoenviron­
ments has proven difficult because long-term, high­
resolution records are sparse. Consequently, paleocli­
matic information for these regions has to be inferred
from other deposits, such as loess, sand dunes, and
soils. Recently, Holliday (2000) reviewed and re­
trieved paleoclimatic information from archaeologi­
cal, geochemical, and geological data from the
Southern High Plains of the Great Plains (site 13 in
Fig. 3). He found climatic oscillations during the
Pleistocene-Holocene transition, especially dry and
warm conditions during the Folsom period 00,9001 0,200 14C BP) as indicated by eolian activity (wind
erosion, eolian deposition), which coincided with the
35 1
YD interval. The Folsom period was drier and possi­
bly warmer than the preceding Clovis period
0 1 ,200- 1 0,900 1 4C BP) and the period after.
6. Causes of climatic oscillations in the interior of
North America
6.1. Local versus broad-scale climatic change
For the Great Lakes region, it has been postulated
that the YD-age climatic reversal and perhaps other
deglacial climatic events were a locally induced cli­
matic change caused by an air mass passing over
cold proglacial lakes. Lewis and Anderson (1 992)
attribute a gradual decrease of 3%0 in Sl80 from
1 1 ,000 to 1 0,500 14C BP in the Lake Erie basin to
the isotopically light meltwater inflow from the high­
stand of proglacial Lake Algonquin in the Lake
Huron basin. Using as analogue the cooling effect of
lowlands west of modem Hudson Bay (Rouse, 199 1 ),
they propose that the lake cooling was responsible
for the Picea recurrence in the southern Great Lakes
region (Shane, 1987) and for pollen anomalies at
other sites. Shane and Anderson (1993) pointed out,
however, that the strongest YD signal is found at
sites distant from the lakes. On the basis of the
stable-isotope and pollen record from a small lake
near Glacial Lake Agassiz during its second expan­
sion, Hu et al. (1 997) showed that lake-induced
cooling in the early Holocene did not cause a signifi­
cant change in vegetation. In the Great Lakes region,
the available data suggest that the detectability of
pollen anomalies during the YD interval relies more
on site location relative to ecotonal vegetation, rather
than on the distance from proglacial lakes or down­
wind/upwind directions (Saamisto, 1974; Shane,
1 987; Wright, 1 989; Yu, 2000).
On the basis of isotopic and lake-level data from
the sediments of Lake Huron and Georgian Bay, Rea
et al. (1994a,b) found that the highstands, including
Lake Algonquin at 1 1 ,200-10,200 14C BP, were
characterised by isotopically heavy water, indicating
-
Fig. 13. Summary pollen percentage and pollen-accumulation rate diagrams of SUbalpine forest taxa at Black Mountain Lake and Sky Pond
in Colorado for the late-glacial and early Holocene period (from Reasoner and Jodry, 2000). These diagrams show clear and rapid response
of alpine timberline vegetation to the Younger Dryas cooling at about 12,900-11 ,500 cal BP.
352
z. Yu, H.E. Wright Jr./ Earth-Science Reviews 52 (200]) 333-369
a much smaller meltwater component relative to
input from local precipitation and run-off. In con­
trast, the intervening lowstands were characterised
by cold, dilute, isotopically very light water. These
new results do not appear to support the Lewis and
Anderson (1989, 1992) hypothesis, although Rea et
ai. (1994b) maintain that lake-effect cooling is prob­
ably related more to surface area than the meltwater
volume. Nevertheless, the relatively warm lake water
during highstands of the Great Lakes certainly would
have had a less pronounced cooling effect. In fact,
the lake areas of Lakes Ontario, Erie, and Michigan
at 1 0,800 1 4C BP were smaller during the main Lake
Algonquin phase than at present, and Lake Huron
was similar in size (see Fig. 2b in Lewis and Ander­
son, 1 992).
The cooling effect of large lakes on adjacent land
does occur. However, the main difficulty with the
Lewis and Anderson hypothesis is how this cooling
effect links to the YD climatic reversal, which re­
quires more enhanced lake and ice-sheet cooling
during the YD interval than before and after. The
extensive ice sheet itself might very well have over­
printed the localized cooling caused by proglacial
lake water by modifying atmospheric circulation and
temperature (Clark et aI., 1999). Because of its size,
Hudson Bay presently generates a distinct air mass
off its coast. During the YD interval, proglacial lakes
would have had a relatively small cooling effect
compared with the extensive ice sheet to the north.
Anderson and Lewis (1 992) also postulated that a
similar meltwater-induced cooling could account for
early-Holocene pollen anomalies at 1 0,000-8000 1 4C
BP summarized in their paper (Fig. 1 1 ). However,
their hypothesis does not predict the PB cooling
found at sites such as Crawford Lake and Twiss
Marl Pond and perhaps the Gage Street and Nichols
Brooks sites, which were distant from any proglacial
lakes at 9500 BP (see Fig. 1 in Anderson and Lewis,
1 992). In fact, the areas of the Great Lakes at 9500
BP, except Lake Superior, were much smaller than
today, and water levels in the Huron and Michigan
basins were near their lowest levels ever (see Fig. 20
in Teller, 1987).
In summary, the hypothesis of local meltwater-in­
duced cooling cannot be applied to the YD-age and
other climatic oscillations recorded in the Great Lakes
region. At some of these small lakes (Fig. 7), the
sequence and relative magnitude of climatic changes
match in detail the records from the North Atlantic
region and indicate that these oscillations are likely
an expression of broad-scale, probably global, cli­
matic changes. This similarity cannot be satisfacto­
rily explained by any local or regional processes, and
it must relate to a more fundamental climatic trigger
in the coupled ocean-atmosphere-ice sheet climatic
system, which would explain these widespread,
abrupt climatic events (Broecker et aI., 1985; Rind et
aI., 1986; Shane, 1 987; Wright, 1 989; Peteet et aI.,
1997; Yu and Eicher, 1 998).
6.2. Transmittal mechanism and response of conti­
nental interior
Recent data indicate that the abrupt warming at
the end of the last glaciation (B!1Illing warming) and
at the end of the YD (Holocene warming) in the
North Atlantic both occurred several decades before
the tropical warming indicated by an increase in
atmospheric methane concentration, suggesting that
the trigger of deglacial climatic oscillations was re­
lated to North Atlantic Ocean rather than to changes
in the tropics (Severinghaus et aI., 1 998; Severing­
haus and Brook, 1 999). Many theories to explain
these deglacial climatic oscillations invoke mecha­
nisms associated with ice sheets and the North At­
lantic Ocean. The mechanisms have long been re­
lated to dynamics of northern hemispheric ice sheets
(ice-sheet forcing; McCabe and Clark, 1 998; Clark et
aI., 1 999) and of oceanic circulation (Broecker et aI.,
1 990) or to external forcing from beyond the North
Atlantic region (Bond and Lotti, 1 995; Goslar et aI.,
2000).
Alley and Clark (1999) recently synthesized evi­
dence and theories on the deglaciation of the North­
ern Hemisphere and on climatic oscillations during
the last deglaciation. They emphasized the impor­
tance of temporal perspectives in discussing mil­
lennial-scale climatic events. The deglaciation was
ultimately a response to increased insolation in Mi­
lankovitch cycles. The D-O oscillations ( ,.., 1 500
years spacing) were usually superimposed on a longer
H-B Cycle with a spacing of 6000- 17,000 years.
The last H-B cycle occurred during the last
deglaciation at the transition from the B!1Illing warm­
ing to the YD ( HO; Andrews et aI., 1 994). Alley
=
Z. Yu, H.E. Wright Jr./ Earth-Science Reviews 52 (200]) 333-369
and Clark (1 999) suggest that millennial-scale warm­
ing and cooling events during the last deglaciation
may represent some combination of response to free
oscillation or oscillations in the climate system, with
forced oscillations linked to changes in the mid-lati­
tude ice sheets. A meltwater-triggered shift in ther­
mohaline circulation in the North Atlantic during the
YD would have had the potential to greatly cool the
high-latitude North Atlantic, Greenland, and Europe.
The YD climatic reversal was possibly, at least in
part, related to meltwater diversion in North America
(Broecker et aI., 1988). However, it was one of many
similar abrupt climatic changes during the last
glaciation and last deglaciation that may have had
multiple causes (Alley and Clark, 1 999; Alley, 2000).
Holocene D-O-like events usually have a variable
spacing of 700-2200 years (Bond et al., 1997); the
8.2-ka cooling event was one of these and has a
geographic pattern similar to that of the YD (Alley et
al., 1997).
A widely accepted hypothesis is that iceberg and
meltwater pulses from wasting ice sheets diluted the
surface ocean with less dense water, thus shifting or
even shutting down the thermohaline circulation
(THC) and North Atlantic Deep Water (NADW)
formation, causing reduced heat transfer from sub­
tropical to subpolar regions and cooling the high
latitudes around the North Atlantic, especially down­
wind, i.e., Europe (Broecker et aI., 1988, 1 989;
Broecker, 1 994, 1997). This mechanism has been
invoked to explain the most prominent cold event
during the last deglaciation, the YD at 12,700- 1 1 ,600
cal BP, by the routing change of the Laurentide ice
sheet meltwater from the Mississippi drainage sys­
tem to the St. Lawrence River (Rooth, 1982). The
cooling effect extended upwind in North America as
far as Ohio (Wright, 1989). Meanwhile areas farther
inland (e.g., Minnesota) were affected not only by
the proximity to the ice sheet in southern Canada but
by the influence of the milder Caribbean air mass,
thereby accounting for non-analogue vegetation that
characterized the region in the late-glacial (see Sec­
tion 6.3 for details). Change in oceanic ventilation
was also associated with the 200-year-Iong PB at
,.., 1 0,900 cal BP (Lehman and Keigwin, 1992;
Bjorck et aI., 1996). The final collapse of ice sheets
and catastrophic drainage of glacial lakes might have
triggered the most prominent Holocene cooling event
353
at 8200 cal BP (Alley et aI., 1997; Barber et aI.,
1 999), although another interpretation of this event
has been offered (Hu et al, 1999).
Although at a global scale the exact causes of
rapid climatic oscillations, including the YD event,
are still incompletely understood, accumulating evi­
dence from different regions and climate modelling
will ultimately shed light on their causes and mecha­
nisms and the Earth' s climatic dynamics as a whole.
Here we assume that the climatic signals during the
last deglaciation originated from meltwater-induced
change in North Atlantic thermohaline circulation, as
indicated by most available empirical evidence, and
we discuss recent modeling results that point to the
mechanism of transmittal of climatic signals into the
continental interior of North America.
The results from general circulation models
(GeMs) suggest possible mechanisms of cause and
transmittal of climatic signals. On the other hand, the
geographic distribution and magnitude of the cli­
matic events, as indicated by empirical records, are
important for testing modeled mechanisms. Different
forcings would result in various climatic responses in
different geographic regions. Using an energy bal­
ance climate model, Harvey (1 989) simulated the
climatic response during the YD to several hypo­
thetical causes, including fresh meltwater lens with
extensive sea ice, iceberg flooding, reduction in
NADW, reduction in northward heat transport, and
reduction in atmospheric CO2 concentration. Rind
and Overpeck (1993) systematically examined the
climatic responses to hypothetical causes/forcings
of climatic variability, including (1) inherent random
variability in the atmosphere; (2) inherent or forced
variability in the ocean system; (3) solar variability;
(4) variability in volcanic aerosol loading in the
atmosphere; and (5) variability in atmospheric trace
gases. By using GISS GCM, Rind and Overpeck
found that different geographic patterns resulted from
different forcings. For example, the cooling of the
North Atlantic due to THC shutdown will affect
mostly those regions adjacent to and downwind of
the North Atlantic. This is apparently the case in
modeling the impact of a cold North Atlantic on YD
cooling (Rind et aI., 1986). In contrast, decreased
insolation would affect all latitudes. However, be­
cause the differential heating of land and ocean
causes regional changes in atmospheric circulations
354
z. Yu, H.E. Wright Jr./ Earth-Science Reviews 52 (20()]) 333-369
and advection patterns, the maximum cooling in
response to decreased insolation tends to occur over
inland regions far removed from oceanic influences
(Rind and Overpeck, 1993; Lean and Rind, 1 998).
This sensitive response of continental interiors to
small solar change was suggested by empirical data
from the northern Great Plains (Yu and Ito, 1999).
Hostetler et ai. (1999) modeled the response of the
climate system during a Heinrich event by using an
atmospheric GCM (GENESIS) and found that mod­
eled temperatures and wind fields exhibit spatially
variable responses over the Northern Hemisphere.
Because different mechanisms have different signa­
tures in time and space, they may allow for discrimi­
nation among climatic records (Rind and Overpeck,
1993).
Recently accumulated evidence for deglacial cli­
matic oscillations from the North Pacific (Kennett
and Ingram, 1 995; Behl and Kennett, 1 996; Hendy
and Kennett, 1999), the west coast of North America
(Engstrom et aI., 1 990; Mathewes, 1 993; Peteet and
Mann, 1994; Benson et aI., 1 997) and Rocky Moun­
tains (Reasoner et aI., 1994; Gosse et aI., 1 995;
Reasoner and Huber, 1 999; Reasoner and Jodry,
2000) indicate synchronous response of the climate
system to the North Atlantic climatic changes. Was
this signal transmitted from the North Atlantic Ocean
to the North Pacific Ocean through the atmosphere
or the ocean? Although the flow of water within the
conveyor from the North Atlantic to North Pacific
takes about 1 000 years (Kennett and Ingram, 1 995),
too slow to explain the near-synchronous climatic
responses, several climatic simulations were con­
ducted to explicitly test the transmittal mechanisms.
To explain the presence of the YD climatic rever­
sal around the North Pacific, Peteet et ai. (1 997)
used an atmospheric general circulation model (GISS)
to test the sensitivity of the Northern Hemisphere air
temperatures to change in North Pacific sea-surface
temperatures. They found that a colder North Pacific
alone has a cooling effect on air temperatures over
North America and suggested that a reduction in
water vapor due to cold ocean temperatures is the
key element that causes the cooling. They also found
dry conditions in southwestern North America in
response to the North Pacific cooling, an effect
supported by paleoclimatic data from Owens Lake
basin (Benson et aI., 1997).
Using the ECHAM3/LSG-coupled ocean-atmo­
sphere general circulation model (OAGCM), Mikola­
jewicz et aI. (1997) found that a cold North Atlantic
could cause North Pacific climatic variability. Dur­
ing the YD interval the temporary shutdown of
NADW formation and a decrease in thermohaline
circulation resulting from meltwater input cooled the
North Atlantic and reduced poleward heat transport.
A maximum cooling occurred over the North At­
lantic and Europe, but a marked cooling over the
entire Northern Hemisphere also occurred. This
downstream cooling reached the North Pacific pri­
marily through the atmosphere, according to simula­
tions of the OAGCM and a radiocarbon tracer model
(Mikolajewicz et aI., 1997). Changes in atmosphere
affect coastal upwelling at the North American west
coast, and the induced surface cooling caused better
ventilation of the thermocline waters of the north­
eastern Pacific.
As shown in Fig. 14, for the Great Lakes region
and the northeastern part of North America the cool­
ing was an upstream effect of a cold North Atlantic,
diminishing inland. This is typical geographic pat­
terns of oceanic climatic forcing (Rind and Over­
peck, 1993). Upstream cooling effects were also
suggested by the atmosphere GCM results, though at
smaller magnitude (Rind et al., 1986; Wright, 1989).
However, the difference of the Mikolajewics et aI.
(1997) simulations from previous model results is
that it used a coupled OAGCM and connected North
Atlantic and North Pacific directly. The relatively
small cooling at the North American west coast is
caused by the intensification of the northward winds
along the coast. The Mikolajewics et aI. simulation
successfully explains the evidence from marine
records in the North Pacific, but it still cannot fully
account for the evidence from the interior of North
America and the west coast reviewed in this paper.
The simulation suggests a small temperature depres­
sion in the region around 45°N and l 00oW. This
region includes the Colorado Rocky Mountains,
where strong evidence for the YD is available from
glacial and pollen records (Menounos and Reasoner,
1 997; Reasoner and Jodry, 2000).
Two empirical studies from western North Amer­
ica (region F and site 1 1 in Fig. 3) discuss the
transmittal mechanisms of the YD signal in relation
to the GeM simulations. Benson et aI. (1997) sug-
Z Yu, H.E. Wright Jr./ Earth-Science Reviews 52 (200]) 333-369
355
Fig. 1 4. Modeled change in mean near-surface air temperature around North America due to a shutdown of North Atlantic Deep Water
formation in the ECHAM3/LSG coupled OAGCM (Mikolajewicz et aI., 1 997). Here shown is the difference between meltwater-induced
NADW shutdown experiment (similar to the Younger Dryas scenario) and control run.
gested that the cooling of the North Pacific de­
creased the temperature and moisture content of the
air mass passing over the middle latitudes of western
North America and caused a drier climate there, as
indicated by their paleoclimate records and climate
simulation model (Peteet et aI., 1 997). Reasoner and
Jodry (2000) found a downslope displacement of the
alpine timberline vegetation during the YD in Col­
orado Rocky Mountains and suggested that change
in atmospheric circulation in the eastern North Pa­
cific would enhance onshore air flow across the
North American Cordillera (Mikolajewics et aI.,
1 997). This enhanced air flow increases orographic
precipitation at higher latitudes and provides favor­
able conditions for the expansion of alpine glaciers,
though the temperature change alone, determined
from the change in timberline vegetation, is suffi­
cient to explain the magnitude of YD glacial ad­
vances in the Rocky Mountains (Reasoner and Jodry,
2(00).
6.3. Amphi-Atlantic contrasts in late-glacial climates
The configuration of the continents framing the
North Atlantic Ocean has strongly influenced the
patterns of air-mass distribution. Under conditions of
changing Milankovitch insolation distribution, this
geography has resulted in the initiation and growth
of the Laurentide ice sheet, and during the deglacia­
tion phase the dynamics of the ice sheet itself con­
trolled the climatic history on both sides of the
Atlantic.
North America east of the Rocky Mountains de­
rives its moisture primarily from the tropical mar­
itime air mass originating over the Caribbean area, as
Pacific maritime air loses most of its moisture in
crossing the Western Cordillera (Fig. 15). The same
maritime air from the Caribbean moves up the North
American east coast and across the Atlantic to Eu­
rope with the prevailing westerly winds. This circula­
tion pattern dominated during the last interglacial
period, and temperatures then were even warmer
than today, as indicated by the small size of the
Greenland ice sheet and by evidence that the arctic
of northern Scandinavia and northwestern Siberia
was less cold than at present (Velichko et aI., 1 997).
The Laurentide ice sheet began to form during an
interval of declining summer insolation and had
spread as far west as the Rocky Mountains by the
time of the last glacial maximum. During this phase
of expansion, the Laurentide ice sheet was nourished
primarily by the moist Caribbean air mass. In Eura­
sia, the accumulation of ice early in the last glacial
period was centered in northwestern Siberia. How­
ever, during the last glacial maximum the Scandina­
vian ice sheet had expanded and effectively blocked
the flow of moisture to the west-Siberian ice, which
became less extensive than it had been earlier
(Velichko et al., 1997; Mangerud et aI., 1 999).
At its maximum and during its wastage, the Lau­
rentide ice sheet indirectly controlled the climate of
Europe. Its height and area, when combined with the
contemporaneous Cordilleran ice sheet, caused the
Westerly Jet Stream to be divided in its course
z
H E.
52 (200}J
Jr.
""" "" ",,' c and A rtemisia i n
and even i n the
Mediterranean lowlands ret1ccted the influence of
the cold Siberian
and the low moisture
content of the cool Atlantic air mass. Trees were
in the Italian and Balkan
confined to
suphighlands (Watts et a1.. 1 996; Will i s, 1
precipitation, although they
ported
lowlands (Willis et aL
penetration
Fig.
1 5.
ScOhemat;c map i Uustrating
the lack
Caribbean air penetration
"viden.:, for a cold Y olinger
dimatic ",,,, illations
c<:!ltral
interior North
the ckglacial period. the climatic signal from the;
the
YD)
WaS transmitted
al.. 1 9X6: Wright.
1 989).
upstream
far as
affecting the Great Lakes
evidence
reviewed in this paper. At the same
far
the Rocky Mountains Pviikobje­
the Pacific
region eaSl of the f{ocky Moun-
Great Lakes the
ardic air mass
Warm Caribhean air
pelldralc
interruption. producing
condiliOlh there. The Caribbean influence is indicated
i.c .. pnsistcocc of wmper­
in spruce fore:-,b, as rcvicwL'u in this paper,
further
s11es.
dewil
Fig . .3 for locafions
paleoclimatic
across the continent, with the southern branch nOUfthe desert basins of the American Southwest
northernmost
and the northern branch
Canada north of the ice sheet (COHMAP
I
arctic air to the North Atlantic and
Siberia. Expanded sea ice shifted the oceanic polar
front far south to the latitude of Portugal, according
to the dominance of
foraminifera (Ruddiman
and McIntyre. 1 98 1 ), and permafrost developed in
Eurasia as far south as the Alps and in Siberia to a
comparable latitude
. Baulin and
I
Cold semi-desert vegetation dominated by
During the glacial period, substantial and rapid
climatic o�cj llations are recorded in the Greenland
ice cores as \vell as in marine cores and telTestriaJ
records. Among these the concentration of ice-rafted
detritus in marine cores ( known as Heinrich events)
represents the discharge of icebergs to the Labrador
Sea and thence around the nonhern gyre (Heinrich,
1 98 8 : Andrews and Tedescco. 1 992; B roecker et aI.,
1 992; Bond et aI, 1 992: Groussett e t al.. j 9(3). The
cap of fresh water caused a reduction in
deep-water formation and the return of the oceanic
polar front to the south. The last main Heinrich-type
event was the YD. During this coo] interval, !cebe;r.g s
were supplemented by meltwater from the retreating
ice sheet of the St. Lawrence River, and later joined
the eastward discharge of Glacial Lake
The YD cooling interrupted the BOA warm period
that had followed dissipation of the previous (H- 1 )
H einrich event. A t this time the oceanic polar
which had moved northward almost to its modern
position (Ruddiman and McIntyre, 1 ( 8 1). returned to
the latitude of Portugal. Near-glacial climatic condi­
tions were restored in Europe and sustained by the
cold Atlantic StOl111S and the cold Siberian air that
was still diverted from the Nonh American m·ctic.
Cold conditions also returned to northeastern North
America, where the cold North Atlantic waters cooled
that portion of the Caribbean air mass moving up the
east coast. The famous " noreasters" of the modern
New England climate are storms characteristic of
this air flow. They may have been strengthened by
tbe anticyclonic circulation around the ice sheet,
wbich produced winds in the St. Lawrence Valley
that were strong enough to orient sand dunes as the
ice retreated to the nonh (Filion, 1 (87). Noreasters
may have been more common and intense in the YD
because of the cooler waters and cooler air mass.
extending as far west as Obio. Model experiments
for the YD suggest that low temperatures resulting
Z Yu, H.E. Wright Jr. / Earth-Science Reviews 52 (2001) 333-369
from an upwind effect extended that far west-but
no farther (Rind et aI.,
1986).
Meanwhile, in southeastern North America and
west as far as the Rocky Mountains, the Caribbean
air mass played a direct and more immediate role in
357
perature extremes found today, for it is this factor
that limits the northern range of these deciduous
trees.
These relations are not fully explained by the
usual numerical climatic reconstructions that com­
the climate of North America during the glacial
pare fossil pollen assemblages with analogous pollen
southeast the very diverse modem tree flora, al­
climatic conditions, which do not include minor but
though not so exceptional as that in southeastern
critical climatic variables such as extremes. Fossil
China in a comparable continental position, rivals
assemblages that are anomalous because they have
comparison led Braun
sis. The lack of analogues for mid-continental assem­
period, even up to the border of the ice sheet. In the
that recorded for the late Tertiary in Europe. This
(1947)
to postulate that the
forests of the southern Appalachian Mountains have
surface samples taken from areas of known mean
no modem analogues are not included in the analy­
blages during deglaciation reflects the interplay of
remained little changed since the Tertiary and were
two major climatic controls that are different from
classic review of Pleistocene biogeography, Deevey
control seasonality and atmospheric circulation, and
not affected by Pleistocene climatic changes. In a
( 1947)
showed that boreal trees like spruce had
indeed invaded the region during glacial periods, and
since then dozens of pollen diagrams in the southeast
have shown that the forests were modified substan­
tially (Watts,
1980)
and that the varied topography
the present-stronger summer insolation patterns that
the existence of a major ice sheet in mid-latitudes. It
is hypothesized that the intervals of extreme cold in
winter such as those experienced today in the mid­
continent did not occur during the glacial period
because arctic air was trapped north of the ice sheet
and
-the very air that was diverted instead over the pole
Farther west in the center of the continent, the
above. The arctic air that did flow south off the ice
provided
habitats
for
warm-temperate trees.
both
cool-temperate
forest vegetation and thus the climatic history during
the glacial and deglacial periods is more difficult to
reconstruct. The evidence is summarized in some
detail below because the contrasts with the European
history are so striking. Pollen studies show that the
climate in the mid-continent south of the Laurentide
ice sheet was dominantly temperate and relatively
stable, contrasting strongly with the dominantly frigid
but oscillating conditions in Europe, despite the fact
that in North America a huge ice sheet was close at
hand, whereas in Europe the Scandinavian ice sheet
was relatively small.
Only a narrow fringe of permafrost existed in
North America south of the ice sheet, for most of the
area north of
50°
was protected from freezing by the
ice sheet itself. Tundra was also restricted-in fact
spruce forest grew on the stagnant ice of terminal
moraines (Florin and Wright,
expansion of spruce forest
1 969). The southward
to 40° latitude indicates
the prevalence of cool summers, but from there north
to the North Atlantic and Siberia, as mentioned
sheet was adiabatically warmed and reduced in hu­
midity, as in foehns or chinooks (Bryson and Wend­
land,
1 967).
Conditions in the periglacial area per­
mitted temperate deciduous trees to survive in the
dominant
spruce
forest,
which
itself
extended
throughout the Midwest because of cool summers
engendered by the ice sheet to the north.
For example, King
(1973)
showed that in Mis­
souri the closed spruce pollen assemblage was suc­
ceeded by an assemblage that he called "spruce with
deciduous elements", dated at about
It contained about
20%
13,500
14C BP.
pollen of oak, elm, iron­
wood, and hazel in an assemblage dominated by
spruce
(30%). A similar combination was found by
(1 954) in southeastern Michigan, where
30% spruce pollen was combined with 30%
Andersen
the
temperate types, which, however, were attributed not
to local occurrence but to redeposition from uniden­
tified older interglaciaLsediments, a common alterna­
tive interpretation of non-analogue assemblages. Ap­
the apparent admixture of temperate decidu­
parently in these regions well south of the ice sheet
Caribbean air mass had an ameliorating effect on the
poraneous with the temperate BOA conditions around
to
50°
ous trees like ash, oak, and elm implies that the
climate, and that winters did not have the low tem-
the winter climate was already ameliorating, contem­
the North Atlantic.
358
Z Yu. H.E. Wright Jr. / Earth-Science Reviews 52 (200]) 333-369
Farther north in the Midwest, a less diverse but
significant admixture of temperate tree taxa also
occurs in the spruce pollen zone. A compilation of
20 pollen' sites in the Minnesota area for the spruce
pollen zone, which dates from about 1 6,000 to 1 1 ,000
1 4C BP, shows about 2-5% each for ash, oak, elm,
and ironwood. Even the underlying herb zone at
many sites has 2-5% oak and ash pollen, although it
may contain macrofossils of tundra plants. This zone
is also marked by pollen of the open-ground temper­
ate plants Artemisia (10-40%) and Ambrosia (51 0%), in addition to the 40% spruce pollen. Many
sites also contain 1 % pollen of Typha, another taxon
rare in the boreal forest today. The modem boreal
forest and forest-tundra of Canada, their closest gen­
eral analogues, lack these temperate taxa, and pollen
surface samples from that region do not show such
values, nor do pollen traps (Ritchie and Lichti­
Federovich, 1 967). It is commonly considered that
unexpected pollen types, if not accounted for by
redeposition, represent distant transport to an area of
low local pollen production. Although this explana­
tion is likely for pine pollen in tundra settings, it is
not valid for the spruce forest that extended even up
to the ice front. Spruce produces abundant pollen,
but, unlike pine pollen, its pollen is not easily trans­
ported long distances by wind. Of course, the finding
of macrofossils provides undeniable evidence for
local occurrence of the plant, but macrofosssils of
the critical temperate plants are notoriously difficult
to find in lake deposits, on which most studies are
made. In Europe, Kullman (1998) reported macro­
fossils of oak, hazel, and elm in an otherwise domi­
nant boreal-forest assemblage in a peat deposit in the
Swedish Mountains at a site well above the modem
range of these temperate taxa dated to the time very
soon after ice retreat. The occurrence of the temper­
ate types in pollen diagrams had previously been
attributed to distant transport. This combination of
boreal and temperate plants has no analogue today in
Scandinavia and can be attributed to the same type
of anomalous climatic conditions called upon below
for the Minnesota assemblage.
Pollen percentages may yield a deceiving picture
of vegetation, and a more accurate estimate of the
pollen deposition of the anomalous types in question
can be made by the determination of pollen influx,
which requires an accurate chronology. One suitable
site for such an estimate is Kylen Lake in northeast­
ern Minnesota (Birks, 1981), where the non-calcare­
ous terrain provides no basis for supposing that the
radiocarbon dates and thus the chronology or influx
calculations are in error. Here in sediments dated
1 3,400 to 12,400 14 C BP, Ambrosia-type pollen
(7%) has an influx of about 200 grains cm - 2 year- 1 ,
Artemisia (10%) an influx of 400, and spruce (20%)
an influx of 800 grains cm - 2 year- I . Similar influx
values were obtained for the spruce pollen zone at
Elk Lake in northwestern Minnesota (Whitlock et aI.,
1 993), Rutz Lake in south-central Minnesota (Wad­
dington, 1 969), and Lake West Okoboji in north­
western Iowa (Van Zant, 1 979). These three sites
were occupied by prairie in the mid-Holocene, when
the influx values of Ambrosia and Artemisia were
generally not much higher than they were in the
late-glacial spruce zone, as prairie plants disperse
much less pollen than trees. The pollen-trap collec­
tions of Ritchie and Lichti-Federovich (I967) in the
modem boreal forest and tundra of Canada contain
only trace amounts of Ambrosia, despite the high
pollen production by this weed in modem agricul­
tural areas of the Great Plains that can provide a
source. These pollen types are unlikely to have
blown to the Minnesota area from the south during
the glacial period, because spruce forest extended at
this time at least as far south as Kansas, and the
closest open land was in Texas, where the pollen
assemblage was dominated by grasses and contained
little Ambrosia.
A hypothetical climatic reconstruction for condi­
tions that would permit the occurrence of Ambrosia
and temperate trees in a landscape dominated by
boreal trees, even containing tundra types like Dryas,
emphasizes the unique conditions of a landscape
bordering a huge ice sheet at a time with substan­
tially higher summer insolation than today-condi­
tions for which we should not anticipate detailed
modem analogues. Winters would not have had the
temperature extremes that today limit the northern
range of temperate hardwoods, because the frigid
arctic air was trapped north of the ice sheet. Where
the landscape had a diversified topography, the spruce
forest would have been confined to sheltered valleys,
and the uplands would have been host to shrubs with
scattered wind-resistant larch trees, as in the modem
rolling landscapes of southern Labrador. Dry habitats
z. Yu, H.E. Wright Jr./ Earth-Science Reviews 52 (200]) 333-369
in the spruce forest, such as sandplains with little
359
ence in the tree diversity in Europe and eastern
Dryas, a
North America. The repeated episodes of major Lau­
cial spruce forest, drifting snow may have protected
matic conditions in Europe reduced the temperate
snowmelt, when the surface was warmed and dried
scape, whereas in southeastern United States not
competition, can be occupied even today by
typical tundra plant. In other openings in the late-gla­
the ground cover from winter winds,
and after
by adiabatic winds and by the high insolation of
late-glacial summers, they could have provided a
habitat for temperate herbs like
Ambrosia.
Anomalous pollen assemblages during the glacial
rentide glaciation and the accompanying severe cli­
tree flora that had characterized the preglacial land­
nearly so many taxa were lost.
An exception to the concept that the Laurentide
ice sheet had a limited role in modifying the late-gla­
cial climate of its periglacial area is emphasized by
and deglacial periods in North America have their
conditions resulting from the unique event involving
The so-called disharmonious vertebrate fau­
Bay, resulting from the penetration of a calving front
counterparts among the fossil beetles (Morgan et aI.,
1 983).
nas of this time (Lundelius et aI.,
1 983)
also indicate
climatic conditions found nowhere today on the con­
tinent.
The Allen'ld-like amelioration of Midwestern cli­
the collapse of the central ice dome over Hudson
up Hudson Strait about
7900
14C BP. When the
collapse occurred, the blockage of frigid arctic air
north of the ice sheet was lost, and the Tyrell Sea
that subsequently occupied the depressed Hudson
mate, occasioned by the steady flow of Caribbean air
Bay lowland was filled with icebergs supplied by
to sustain spruce, expanded northward after the last
Keewatin. The frigid air mass that was generated
modulated by the cool periglacial summers necessary
major ice advance in Iowa (Des Moines lobe,
14C BP). It reached southern Minnesota by
1 4,000
1 2,000
14C BP, when spruce pollen started a rapid decline in
favor of early-successional tress (ash, birch, and
remaining portions of the ice sheet in Quebec and
over the cold sea swept southward even in summer,
resulting in an abrupt decrease in values of 8180 of
calcite in the varved sediments of Deep Lake in
northern Minnesota, according to the chronology and
alder), followed by elm and oak. In areas farther
hypothesis of Hu et aI.
warming was abruptly interrupted by the YD, which
seaboard, is unlike the earlier late-glacial fluctuations
east, e.g., from Ohio eastward, this Aller0d-type
brought the return of spruce, fir, and larch, followed
immediately by pine, which had been progressing
rapidly westward from ice-age refuges in the Ap­
palachian highlands. Pine was blocked in its expan­
sion beyond Ohio because the climate was already
too warm, not having been affected by the YD
(1 999).
This event, which is
weakly recorded if at all around the North Atlantic
such as the YD, for it was a local mid-continent
direct response to the Laurentide ice sheet control,
rather than an upwind or downwind reflection of a
North Atlantic event.
In summary, once the Laurentide ice sheet was
built by moisture primarily supplied by the Caribbean
cooling, and to the north it was blocked by Lake
air mass, that ice sheet provided the principal control
its
during full-glacial time by the rerouting of arctic air
Michigan and the ice sheet. When the ice sheet and
proglacial
lakes
withdrew, pine moved very
rapidly into Wisconsin and Minnesota, replacing the
early successional forest and, to the north, the spruce
forest itself.
This vegetational sequence west of the Great
Lakes reflects the direct influence of the Caribbean
on the climate of Europe. This was accomplished
and during deglacial Heinrich events and the YD
interval by the yield of meltwater to the North
Atlantic. Icebergs were of particular importance be­
cause of their stored "coldth". In contrast, the Scan­
dinavian ice sheet had little direct influence on Euro­
air mass in that area throughout the deglacial period,
pean climatic events; rather, it expanded and decayed
underwent the strong climatic perturbations that were
forces, just as did the glaciers in Britain and the
gression of the Laurentide ice sheet, which of course
to the north of the Laurentide ice sheet and its
while areas farther east and especially in Europe
themselves an indirect effect of the deglaciation pro­
was built up by the Caribbean air mass in the first
place. The contrast is also represented by the differ-
in response to the Atlantic and Siberian climatic
Alps. In this reconstruction, the trapping of arctic air
diversion to the east also allowed Caribbean air to
penetrate deeply into the interior of North America
z. Yu. H.E. Wright ir. / Earth-Science Reviews 52 (200]) 333-369
360
(Fig.
1 5).
The striking climatic oscillations in Europe
during the deglacial period thus contrasted strongly
proxy data, especially if proxy records are able to
reveal climatic information concerning extremes or
with the more uniform and temperate conditions of
seasonality rather than usual average climates.
and west of the Great Lakes.
7.2. Site characteristics and selection strategy
7. Future research directions
for a paleoecological signal from large lakes, such as
interior North America east of the Rocky Mountains
Because complicated factors may be responsible
the Great Lakes, small lake sites seem to be more
7.1. Multiple proxy studies
suitable for detecting late-glacial climatic changes.
The regional variations in evidence for the YD
event as summarized above suggest the different
expression of the YD in paleoecological records,
depending on geographic location and character of a
particular site. In some regions, the YD event may
not be expressed as a cold interval (see An et aI.,
1 993;
Roberts et aI.,
1 993; Kneller and
Peteet,
1 999).
The clear evidence from Crawford Lake and other
small sites in the eastern Great Lakes region implies
that the site characteristics are important in providing
suitable isotopic records. Sites in climatically sensi­
tive ecotonal regions are especially suitable for pale­
oclimatic studies. High sampling resolution is re­
quired for detecting brief century-scale events.
In humid temperate regions, oxygen isotopes can
Some proxies may be silent due to their insensitivity
be used as indicator of air temperatures, but in
insensitive
indirectly through evaporation. Thus, non-climatic
to climatic change at the critical time, for example,
(Shane,
response
1 987;
Wright,
of
non-ecotonal
vegetation
Stable isotopes appear
noises, such as from local hydrological change,
Thus, more investigations
tion. Otherwise, strong noise from local hydrological
1 989).
to be very sensitive to climatic change (Wright,
1984;
Ammann,
2000).
are needed on stable-isotope analysis of carbonates
from central North America. In circumstances where
bulk sedimentary carbonates are not reliable for pale­
oclimatic research, carbonate shells of molluscs and
ostracodes may be used (e.g., Lister,
Grafenstein et aI.,
1 998).
1 992, 1 998, 1999;
1988;
von
Yu and Eicher,
At some lakes carbonates may be totally
lacking, and in these cases, cellulose of aquatic
macrophytes or
hydrogen
isotopes
of individual
biomarkers may provide an alternative (Krishna­
murthy et al.,
1 995;
semi-arid and arid regions they may reflect climate
Sauer et al.,
1 999).
The use of multiple proxy records has the poten­
tial to add significant detail to the nature of climatic
change. The multiproxy records from the eastern
Great Lakes region may correlate with records from
the Atlantic Seaboard but may imply climatic changes
of a different nature, such as changes in seasonality
and balance of thermal and moisture conditions,
rather than simply temperature and precipitation. It is
essential to have multiple proxy data to investigate
many different aspects of the YD and other climatic
should be considered in a paleoclimatic investiga­
effects may obscure the climatic signals from stable
isotopes.
8. Summary
(1)
In the Great Lakes region paleoclimatic inter­
pretation of oxygen-isotope records from several
small lakes indicates a classic climatic sequence
during the last deglaciation that is comparable with
records from Europe and Greenland. Some of these
climatic oscillations, especially the YD cold reversal,
have also been recorded in upland and aquatic vege­
tation and glacier readvances.
(2)
Along the Rocky Mountains, the YD event is
recorded by alpine glacier advance at sites from
Alberta to Colorado and by shift in timberline vege­
tation in Colorado.
(3)
In the interior region between the Rocky
Mountains and the Great Lakes, evidence for these
climatic oscillations are generally lacking. However,
oscillations. The apparent contrast in late-glacial cli­
in the southern High Plains dry and warm climatic
lantic region could also be tested using multiple
coincide with the YD interval.
mates between central North America and the At­
conditions as indicated by eolian activity appeared to
361
Z Yu, HE Wright fr./ Earth-Science Reviews 52 (200]) 333-369
(4) The regional variations in climatic evidence
suggest that climatic oscillations may have different
expression . in paleo-records, depending on geo­
graphic location and characteristics of a particular
site. Small lakes with limited local hydrological
complications in climatically sensitive ecotonal re­
gions are ideal for paleoclimatic investigation. The
use of multiple proxy records has the potential to
reveal the nature of climatic change, such as change
in seasonality and extremes.
(5) The geographic extent and magnitude of the
deglacial climatic oscillations across North America
suggest that they are an expression of widespread
climatic changes rather than locally induced events.
Together with simulation results from general circu­
lation models, the compiled evidence suggests that
climatic signals were likely carried over the North
Hemisphere through the atmosphere, producing ei­
ther upwind ( the Great Lakes region) or downwind
effects (the Rocky Mountains) .
(6) The lack of evidence for a cold YD and other
climatic oscillations in interior North America east
of the Rocky Mountains and west of the Great Lakes
was probably caused by the trapping of cold arctic
air mass north of the Laurentide ice sheet and by
uninterrupted northward penetration of warm
Caribbean air. This strongly contrasted climate also
produced more temperate conditions and non-analo­
gous biological assemblages in this region.
1998. Icing the North Atlantic. Nature 392, 335-336.
2000. The Younger Dryas cold interval as viewed
from central Greenland. Quat. Sci. Rev. 19, 213-226.
Alley, R.B., Clark, P., 1999. The deglaciation of the northern
Alley, R.B.,
Alley, R.B.,
hemisphere: a global perspective. Annu. Rev. Earth Planet.
Sci.
27, 149-182.
Alley, R.B., Meese, D.A., Shuman, c.A., Gow, AJ., Taylor,
KC., Grootes, P.M., White, J.W.c., Ram, M., Waddington,
E.D .• Mayewski, P.A., Zielinski, G.A.,
1993. Abrupt increase
in Greenland snow accumulation at the end of the Younger
Dryas event. Nature
362, 527-529.
Alley, R.B., Mayewski, P.A., Sowers, T., Stuiver, M., Tayler,
KC.,
Clark, P.U.,
1 997. Holocene climatic instability: a
8200 yr ago. Geology 25, 483-
prominent, widespread event
486.
Ammann, B.,
1 989. Response times in bio- and isotope stratigra­
phies to late-Glacial climatic shifts, an example from lake
82, 183- 190.
2000. Biotic responses to rapid climatic changes:
deposits. Eclogae Geol. Helv.
Ammann, B.,
introduction to a multidisciplinary study of the Younger Dryas
and minor oscillations on an altitudinal transect in the Swiss
159, 191-20 1 .
1989. Late-Glacial radiocarbon- and
palynostratigraphy on the Swiss Plateau. Boreas 18, 109-1 26.
Alps. Palaeogeogr., Palaeoclimatol., Palaeoecol.
Ammann, B., Lotter, A.,
Ammann, B., Lotter, A.F., Eicher, U., Gaillard, M.-J., Wohlfarth,
B.,
Haeberli,
W.,
Lister,
G.,
Maisch,
M.,
Niessen,
F.,
1994. The Wiirmian Late-glacial in lowland
Switzerland. J. Quat. Sci. 9, 1 1 9-125.
Schliichter, Ch.,
Ammann, B., Birks, HJ.B., Brooks, SJ., Eicher, U., von Grafen­
stein, U., Hofmann, W., Lemdahl, G., Schwander, J., Tobol­
ski, K, Wick, L.,
2000. Quantification of biotic responses to
rapid climatic changes around the Younger Dryas-a synthe­
sis. Palaeogeogr., Palaeoclim., Palaeoecol. 159, 3 1 3-347.
An, Z.S., Porter, S.C., Zhou, W., Lu, Y., Donahue, DJ., Head,
MJ., Wu, X., Ren, J., Zheng, H., 1993. Episode of strength­
ened summer monsoon climate of Younger Dryas age on the
39, 45-54.
1954. A late-glacial pollen diagram from southern
Michigan, USA. Dan. Geol. Unders., II Raekke, Nr. 80,
140- 155.
Anderson, T.W., Lewis, C.F.M., 1992. Climatic influences of
deglacial drainage changes in southern Canada at 10-8 ka
suggested by pollen evidence. Geogr. Phys. Quat. 46, 255-272.
Anderson, T.W., MacPherson, J.B., 1994. Wisconsinan late-gla­
Loess Plateau of Central China. Quat. Res.
Acknowledgements
We thank Femke Wallien (Earth Sciences­
Elsevier Science BV) for her suggestion of writing
this review; Ueli Eicher and contributors of data sets
used in this review for making numerical data avail­
able; and Brigitta Ammann, Bob Johnson, Mel Rea­
soner, Pierre Richard and Bryan Shuman for helpful
suggestions and comments on the manuscript. This is
Limnological Research Center contribution 5 bs.
Andersen, S.T.,
cial environmental changes in Newfoundland: a regional re­
view. J. Quat. Sci.
paleoclimate following the Younger Dryas. Geology
1 996. Oxygen-isotope record of Late-Glacial climatic change
in western Ireland. Boreas 25, 257-267.
25, 135-
138.
1994. Wisconsinan Late-glacial environmental
change on the southeast Baffin shelf, southeast Baffin Island
9, 179-183.
1 992. Detrital carbonate-rich sedi­
and northern Labrador. J. Quat. Sci.
Andrews, J.T., Tedesco, K,
Ahlberg, K, Almgren, E., Wright Jr., H.E., Ito, E., Hobbie, S.,
1997. Stable isotope
record from Seneca Lake, New York: evidence for a cold
Andrews, J.T.,
References
9, 1 7 1 - 178.
Anderson, W.T., Mullins, H.T., Ito, E.,
ments, northwestern Labrador Sea: implications for ice-sheet
dynamics and iceberg rafting (Heinrich) events in the North
Atlantic. Geology
20, 1087- 1090.
362
z. Yu. H.E. Wright Jr./ Eanh-Science Reviews 52 (2001) 333-369
Andrews. J.T Erlenkeuser. H Tedesco. K. Aksu, A., Jull,
A.J.T., 1 994. Late Quaternary (stages 2 and 3) meltwater and
Heinrich events, NW Labrador Sea. Quat. Res. 41, 26-34.
Atkinson, T.e., Briffa, KR, Coope, G.R, 1987. Seasonal temper­
atures in Britain during the past 22,000 years, reconstructed
using beetle remains. Nature 325. 587-593.
Barber, D.C., Dyke, A., Hillaire-Marcel, C., Jennings, A.E., An­
drews, J.T., Kerwin, M.W., Bilodeau, G., McNeely, R,
Southon, J., Morehead, M.D., Gagnon, J.-M., 1999. Forcing of
the cold event of 8,200 years ago by catastrophic drainage of
Laurentide lakes. Nature 400, 344-348.
Baulin, V.V., Danilova, N.S., 1 984. Late quaternary permafrost in
Siberia. In: Velichko, A., Wright, H.E. Jr., Barnosky, C.
(Eds.), Late Quaternary Environments of the Soviet Union.
University of Minnesota Press, Minneapolis, MN, pp. 60-78.
Behl, RJ., Kennett, J.P., 1996. Brief interstadial events in the
Santa Barbara Basin, NE Pacific, during the last 60 kyr.
Nature 379, 243-246.
Bender, M., Sowers, T., Dickson, M.-L., Orchardo, J., Grootes,
P., Mayewski, P.A., Meese, D.A., 1994. Climate correlations
between Greenland and Antarctica during the past 100,000
years. Nature 372, 663-666.
Benson, L., Burdett, J., Lund, S., Kashgarian, M., Mensing, S.,
1 997. Nearly synchronous climate change in the Northern
Hemisphere during the last glacial termination. Nature 388,
263-265.
Berglund, B.E., Bjorck., S., Lemdahl, G., Bergsten, H., Nordberg,
K, Kolstrup, E., 1994. Late Weichselian environmental change
in southern Sweden and Denmark. 1. Quat. Sci. 9, 1 27- 1 32.
Birks, H.1.B., 1981. Late Wisconsin vegetational and climatic
history of Kylen Lake, northeastern Minnesota. Quat. Res. 16,
322-355.
Birks, H.H., Ammann, B., 2000. Two terrestrial records of rapid
climatic change during the glacial-Holocene transition
( 14,000-9,000 calendar years B.P.) from Europe. Proc. Natl.
Acad. Sci. U. S. A. 97, 1390-1 394.
Bjorck, S., 1985. Deglaciation chronology and revegetation in
northwestern Ontario. Can. J. Earth Sci. 20, 850-87 1 .
Bjorck, S., Berglund, B.E., Digerfeldt, G., 1988. New aspects on
the deglaciation chronology of southern Sweden. Geogr. Pol.
55, 37-49.
Bjorck, S., Kromer, B., Johnsen, S., Bennike, 0., Hammarlund,
D., Lemdahl, G., Possnert, G., Rasmussen, T.L., Wohlfarth,
B., Hammer, C.U., Spurk, M., 1996. Synchronized terrestrial­
atmospheric deglacial records around the North Atlantic. Sci­
ence 274. 1 1 55-1 1 60.
Bjorck. S., Walker, M.1.C.. Cwynar, L.C., Johnsen, S., Knudsen,
K-L., Lowe, J.1., Wohlfarth, B., INTIMATE Members. 1998.
An event stratigraphy for the Last Termination in the North
Atlantic region based on the Greenland ice-core record: a
proposal by the INTIMATE group. J. Quat. Sci. 13, 283-292.
Blunier, T., Schwander, 1., Stauffer, B., Stocker, T., Diillenbach,
A.. Indermiihle, A., Tschumi, J Chappel1az, 1., Raynaud, D.,
Barnola, J.-M., 1997. Timing of the Antarctic Cold reversal
and the atmospheric CO2 increase with respect to the Younger
Dryas event. Geophys. Res. Lett. 24, 2683-2686.
.•
.•
.•
Blunier, T.. Chappellaz, J., Schwander, J., Diillenbach, A., Stauf­
fer, B., Stocker, T.F., Raynaud, D., Jouzel, J., Clausen, H.B.,
Hammer, C.U., Johnsen, S.1., 1998. Asynchrony of Antarctic
and Greenland climate change during the last glacial period.
Nature 394. 739-743.
Bohncke, S.1.P., 1993. Late glacial environmental changes in the
Netherlands: spatial and temporal patterns. Quat. Sci. Rev. 12,
707-7 1 8.
Bond, G., Lotti, R, 1995. Iceberg discharges into the North
Atlantic on millennial time scales during the last glaciation.
Science 267, 1005-1010.
Bond, G., Heinrich, H Broecker, W.S., Labeyrie, L., McManus,
J., Andrews, J.T., Huon, S., Jantschik, R, Clasen, S., Simet,
c., Tedesco, K, Klas, M., Bonani, G., Ivy, S., 1992. Evidence
for massive discharges of icebergs into the glacial Northern
Atlantic. Nature 360. 245-249.
Bond, G., Broecker, W., Johnsen, S McManus, 1., Labeyrie, L.,
Jouzel, J., Bonani, G., 1993. Correlations between climate
records from North Atlantic sediments and Greenland ice.
Nature 365, 143-147.
Bond, G., Showers, W., Cheseby, M., Lotti, R. Almasi, P.,
deMenocal, P Priore, P., Cullen, H., Hajdas, 1., Bonani, G.,
1997. A pervasive millennial-scale cycle in North Atlantic
Holocene and glacial climates. Science 278, 1257-1 266.
Braun, E.L., 1947. Development of the deciduous forests of
eastern North America. Ecol. Monogr. 17, 21 1 -219.
Broecker, W.S., 1994. Massive iceberg discharges as triggers for
global climate change. Nature 372, 421 -424.
Broecker, W.S., 1997. Thermohaline circulation, the Achilles heel
of our climate system: will manmade CO2 upset the current
balance? Science 278, 1582-1588.
Broecker, W.S., Peteet, D.M., Rind, D., 1985. Does the ocean­
atmosphere system have more than one stable mode of opera­
tion? Nature 3 1 5, 21 -26.
Broecker, W.S., Andree, M., Wolfli, W., Oeschger, H., Bonani,
G. et aI., 1988. The chronology of the last deglaciation:
implications to the cause of the Younger Dryas event. Paleo­
ceanography 3, 1 - 19.
Broecker, W.S., Kennett, J.P., Flower. B.P., Teller, J.T., Trum­
bore, S., Bonani, G Wolfli, W., 1989. Routing of meltwater
from the Laurentide Ice Sheet during the Younger Dryas cold
episode. Nature 341 , 3 1 8-32 1 .
Broecker, W.S., Bond, G., Klas, M., Bonani, G., Wolfli, W.,
1990. A salt oscillator in the glacial Atlantic? 1. The concept.
Paleoceanography 5, 469-477.
Broecker, W.S., Bond. G., McManus, J., Kla�, M., Clark. E.,
1 992. Origin of the Northern Atlantic's Heinrich events. Clim.
Dyn. 6, 265-273.
Brook, E.1., Harder, S., Severinghaus, J., Steig, E.1., Sucher,
C.M., 2000. On the origin and timing of rapid changes in
atmospheric methane during the last glacial period. Global
Biogeochem. Cycles 14, 559-572.
Brooks, S.1., Mayle, F.E., Lowe, J.J., 1997. Chironomid-based
late glacial climatic reconstruction for southeast Scotland. J.
Quat. Sci. 1 2, 1 6 1 - 167.
Bryson, R.A., Wendland, W.M., 1967. Tentative climatic patterns
.•
.•
.•
.•
Z Yu, H.E. Wright Jr. / Eanh-Science Reviews 52 (2001) 333-369
for some late-glacial and post-glacial episodes in central North
America. In: Mayer-Oakes, W.J. (Ed.), Life, Land, and Water.
University of Manitoba Press, Winnipeg, Manitoba, pp. 27 1 298.
Chappellaz, J., Blunier, T., Raynaud, D., Barnola, J.-M., Schwan­
der, J., Stauffer. B., 1993. Synchronous changes in atmo­
spheric CH and Greenland climate between 40 and 8 kyr BP.
4
Nature 366, 443-446.
Clark. D.H., Gillespie, A.R, 1997. Timing and significance of
late-glacial and Holocene cirque glaciation in the Sierra
Nevada, California. Quat. Int. 38/39, 2 1 -38.
Clark, P.U., Alley, RB .. Pollard, D., 1999. Northern Hemisphere
ice-sheet influences on global climate change. Science 286,
1 104- 1 1 1 1.
COHMAP Members, 1988. Climatic changes of the last 18,000
years: observations and model simulations. Science 241,
1043-1052.
Coope, G.R, 1977. Fossil coleopteran assemblages as sensitive
indicators of climatic changes during the Devensian (last) cold
stage. Philos. Trans. R Soc. London, Ser. B 280, 3 1 3-340.
Coope, G.R, Lemdahl, G., 1995. Regional differences in the
Late-glacial climate of northern Europe based on coleopteran
analysis. J. Quat. Sci. 10, 391 -395.
Coope, G.R, Lemdahl, G., Lowe, J.J., Walkling, A., 1998. Tem­
perature gradients in northern Europe during the last glacial­
Holocene transition 04-9 1 4 C kyr BP) interpreted from
coleopteran assemblages. 1. Quat. Sci. 13, 4 19-433.
Cwynar, L.C., Levesque, A.J., 1995. Chironomid evidence for late
glacial climatic reversals in Maine. Quat. Res. 43, 405-413.
Cwynar, L.e., Watts, W.A., 1989. Accelerator-mass spectrometer
dates from the bogs of Ballybetagh, Ireland. Quat. Res. 3 1 ,
377-380.
Cwynar, L.C., Levesque, A.J., Mayle, F.E., Walker, I., 1994.
Wisconsinan Late-glacial environmental change in New
Brunswick: a regional synthesis. J. Quat. Sci. 9, 1 6 1 - 1 64.
Dansgaard, W., White, J.W.C., Johnsen, S.J., 1989. The abrupt
termination of the Younger Dryas event. Nature 339, 532-533.
Dansgaard, W., Johnsen, S., Clausen, H., Dahl-Jensen, D., Gunde­
strup, N .. Hammer, C., Hvidberg, e., Steffensen, J., Svein­
bjornsdottir, A., Jouzel, J., Bong, G., 1993. Evidence for
general instability in past climate from a 250 kyr ice-core
record. Nature 364, 2 1 8-220.
Davis, P.T., 1988. Holocene glacier fluctuations in the American
Cordillera. Quat. Sci. Rev. 7, 129-157.
Deevey, E.S., 1 947. Biogeography of the Pleistocene. Geol. Soc.
Am. Bull. 60, 1 3 16-1416.
Denton, a.H., Hendy, C.H 1 994. Younger Dryas age advance of
Franz Josef Glacier in the southern Alps of New Zealand.
Science 264, 1434-1437.
Eicher, U., 1980. Pollen-und Sauerstoffisotopenanalysen an
spatglazialen Profilen vom Gerzensee, Faulenseemoos und
vom Regenmoos ob Boitigen. Mitt. Natur. Ges. Berne, N.F.
37, 65-80.
Eicher, U., 1987. Die spatglazialen sowie fr\ihpostglazialen Kli­
maverhaltnisse in Bereiche der Alpen: Sauerstoffisotopenkur­
ven kalkhaltiger Sedimente. Geogr. Helv. 2, 99- 104.
Eicher, U., Siegenthaler, U., 1976. Palynological and oxygen
.•
363
isotope investigations on Late-Glacial sediment cores from
Swiss lakes. Boreas 5, 109-1 17.
Elias, S.A., 1997. The mutual climatic range method of palaeocli­
mate reconstruction based on insect fossils: new applications
and interhemispheric comparisons. Quat. Sci. Rev. 16, 12171225.
Elias, S.A., Anderson, K.H., Andrews, J.T., 1996. Late Wisconsin
climate in northeastern USA and southeastern Canada, recon­
structed from fossil beetle assemblages. J. Quat. Sci. II,
417-42 1 .
Engstrom, D.R., Hansen, B.C.S., Wright Jr., H.E., 1990. A possi­
ble Younger Dryas record in southeastern Alaska. Science
250, 1383-1385.
Filion, L., 1987. Holocene development of parabolic dunes in the
central St Lawrence lowland, Quebec. Quat. Res. 28, 196-209.
Florin, M.-B., Wright Jr., H.E., 1969. Diatom evidence for the
persistence of stagnant glacial ice in Minnesota. Geol. Soc.
Am. Bull. 80, 695-704.
Fritz, P., 1983. Paleoclimatic studies using freshwater deposits
and fossil groundwater in central and northern Canada. Palaeo­
climates and Palaeowaters: A Collection of Environmental
Isotope Studies. International Atomic Energy Agency, Vienna,
pp. 157- 1 66.
Fritz, P., Anderson, T.W., Lewis, e.F.M., 1975. Late-Quaternary
climatic trends and history of Lake Erie from stable isotope
studies. Science 1 90, 267-269.
Fritz, P., Morgan, A.V., Eicher, U., McAndrews, J.H., 1987.
Stable isotope, fossil Coleoptera and pollen stratigraphy in late
Quaternary sediments from Ontario and New York State.
Palaeogeogr., Palaeoclimatol., Palaeoecol. 58. 183-202.
Goslar, T., Kuc, T., Ralska-Jasiewiczowa, M., Rozanski, K.,
Arnold, M., Bard, E., van Geel, B., Pazdur, M.F., Szerozyn­
ska, K., Wicik, B., Wieckowski, K., Walanus, A., 1993.
High-resolution lacustrine record of the Late Glacial /Holo­
cene transition in Central Europe. Quat. Sci. Rev. 12, 287-294.
Goslar, T., Arnold, M., Bard, E., Kuc. T., Pazdur, M.F., Ralska­
Jasiewiczowa, M., Rozanski, K .. Tisnerat, N., Walanus, A.,
Wick, B., Wieckowski, K., 1995. High concentration of atmo­
spheric 14C during the Younger Dryas cold episode. Nature
377, 414-417.
Goslar, T., Arnold, M., Tisnerat-Laborde, N., Czernik, J., Wieck­
owski, K., 2000. Variations of Younger Dryas atmospheric
radiocarbon explicable without ocean circulation changes. Na­
ture 403, 877-880.
Gosse, J.e., Evenson, E.B., Klein, J., Lawn. B., Middleton, R,
1995. Precise cosmogenic 10 Be measurements in western North
America: support for a global Younger Dryas cooling event.
Geology 23, 877-880.
Grigg, L.D., Whitlock, C., 1998. Late-glacial vegetation and
climate change in western Oregon. Quat. Res. 49, 287-298.
Grootes, P.M., Stuiver, M., 1997. Oxygen 18/16 variability in
Greenland snow and ice with 1 0 - 3 _ to l OS-year time resolu­
tion. J. Geophys. Res. C 1 02, 26455-26470.
Grootes, P.M., Stuiver, M White, J.W.C., Johnsen, S., Jouzel, J.,
1993. Comparison of oxygen isotope records from the GISP2
and GRIP Greenland ice cores. Nature 366, 552-554.
Grousset, F.E., Labeyrie, L., Sinko, J.A., Cremer, M., Bond, G. et
.•
z. Yu, H.E. Wright Jr. / Eanh-Science Reviews 52 (200n 333-369
364
al.. 1993. Patterns of ice-rafted detritus in the glacial North
Atlantic (40-55°N). Paleoceanography 8. 175- 192.
Hammarlund. D., Edwards. T.W.D., Bjorck. S., Buchardt. B
Wohlfarth. B.. 1 999. Climate and environment during the
Younger Dryas (GS-I) as reflected by composite stable iso­
tope records of lacustrine carbonates at Torreberga, southern
Sweden. J. Quat. Sci. 14. 17-28.
Hansen. B.C.S.. 1995. A review of late-glacial pollen records
from Ecuador and Peru with reference to the Younger Dryas
event. Quat. Sci. Rev. 14, 853-865.
Hansen. B.C.S Engstrom, D.R., 1 996. Vegetation history of
Pleasant Island. southeastern Alaska. since 1 3,000 yr B.P.
Quat. Res. 46. 161- 175.
Harvey. L.D.D 1989. Modelling the Younger Dryas. Quat. Sci.
Rev. 8, 137- 149.
Hebda, R.I 1983. Late-glacial and postglacial vegetation history
at Bear Cove Bog. northeast Vancouver Island. B.C. Can. J.
Earth Sci. 61. 3 173-3192.
Heine. J.T 1998. Extent, timing, and climatic implications of
glacier advances on Mount Rainer. Washington, USA, at the
Pleistocene/Holocene transition. Quat. Sci. Rev. 17. 1 1391 148.
Heinrich. H.. 1988. Origin and consequences of cyclic ice rafting
in the Northeast Atlantic Ocean during the past 1 30.000 years.
Quat. Res. 29. 143-1 52.
Hendy, I.L.. Kennett. J.P.. 1999. Latest Quaternary North Pacific
surface-water responses imply atmosphere-driven climate vari­
ability. Geology 27, 291 -294.
Heusser. CJ .. 1973. Environmental sequence following the Fraser
advance of the Juan de Fuca lobe. Washington. Quat. Res. 3,
284-306.
Heusser, CJ 1977. Quaternary palynology of the Pacific slope of
Washington. Quat. Res. 8. 282-306.
Hoek. W.Z 1 997. Late-glacial and early Holocene climatic events
and chronology of vegetation development in the Netherlands.
Veg. Hist. Archaeobot. 6. 197-213.
Holliday. V.T 2000. Folsom drought and episodic drying on the
Southern High Plains from 10,900-10,200 1 4 C yr B.P. Quat.
Res. 53. 1 - 12.
Hostetler. S.W Clark, P.U., Bartlein. P.J Mix. A.C Pisias.
NJ., 1 999. Atmospheric transmission of North Atlantic Hein­
rich events. J. Geophys. Res. D 104. 3947-3952.
Hu. F.S Wright Jr H.E Ito. E Lease. K 1997. Climatic
effects of glacial Lake Agassiz in the midwestern United
States during the last deglaciation. Geology 25. 207-210.
Hu. F.S .. Slawinski. D Wright Jr H.E Ito. E Johnson, R.G
Kelts. K.R.. McEwan. R.F., Boedigheimer. A.. 1999. Abrupt
changes in North American climate during early Holocene
times. Nature 400. 437-440.
Hughen. K.A., Overpeck. J.T Peterson. L.C., Trumbore. S ..
1996. Rapid climate changes in the tropical Atlantic region
during the last deglaciation. Nature 380, 5 1 -54.
Huntley. B .. Birks, HJ.B., 1983. An Atlas of Past and Present
Pollen Maps for Europe: 0- 13.000 Years Ago. Cambridge
Univ. Press. Cambridge. UK.
Isarin. R.F.B., Bohncke, SJ.P., 1999. Mean July temperatures
.•
.•
.•
.•
.•
.•
.•
.•
.•
.•
.•
.•
.•
.•
.•
.•
.•
.•
.•
.•
.•
.•
during the Younger Dryas in northern and central Europe as
inferred from climate indicator plant species. Quat. Res. 5 1 ,
158-173.
Isarin, R.F.B., Renssen, H., 1999. Reconstructing and modelling
Late Weichselian climates: the Younger Dryas in Europe as a
case study. Earth Sci. Rev. 48, 1-38.
Isbele. G.A .. Hooghiemstra, H., van der Borg, K., 1995. A
cooling event during the Younger Dryas chron in Costa Rica.
Palaeogeogr., Palaeoclimatol.. Palaeoecol. 1 17, 73-80.
Iversen, J 1954. The Late-Glacial flora of Denmark and its
relation to climate and soil. Dan. Geol. Unders. Ser. II 80,
87- 1 19.
Ivy-Ochs, S., Schluchter, C., Kubik, P.W., Synal. H.-A.. Beer, J
Kerschner, H 1996. The exposure age of an Egesen moraine
at Julier Pass, Switzerland measured with the cosmogenic
radionuclides lO Be. 26AI, and 36Cl. Eclogae Geol. Helv. 89,
1049- 1063.
Jacobson Jr., G.L., Webb III. T., Grimm, E.C., 1987. Patterns and
rates of vegetation change during the deglaciation of eastern
North America. In: Ruddiman, W.F., Wright, H.E. Jr. (Eds.).
North America and Adjacent Oceans during the Last Deglacia­
tion. Geological Society of America, Boulder, CO, pp. 277288.
Johnsen. SJ., Clausen. H.B., Dansgaard, W., Fuhrer, K.. Gunde­
strup, N., Hammer. C.U., Iversen. P., Jouzel, J., Stauffer. B.,
Steffensen, J.P., 1992. Irregular glacial interstadials recorded
in a new Greenland ice core. Nature 359, 31 1-313.
Kennett, J.P., Ingram, B.L.. 1995. A 20,000-year record of ocean
circulation and climate change from the Santa Barbara basin.
Nature 356, 357-362.
King. J.E., 1973. Late Pleistocene palynology and biogeography
of the western Missouri Ozarks. Ecol. Monogr. 43, 539-565.
Kneller. M., Peteet, D., 1999. Late-glacial and early Holocene
climate changes from a central Appalachian pollen and macro­
fossil record. Quat. Res. 5 1 , 133- 147.
K� Karpuz. N., Jansen, E., 1 992. A high resolution diatom
record of the last deglaciation from the S.E. Norwegian Sea:
documentation of rapid climatic changes. Paleoceanography 7.
499-520.
Krishnamurthy. R.V., Syrup, K.A., Baskaran. M .. Long, A 1 995.
Late glacial climate record of midwestern United States from
the hydrogen isotope ratio of lake organic matter. Science 269,
1565-1567.
Kuhry, P., Hooghiemstra. H.. van Geel, B., van der Hammen, T.,
1 993. The EI Abra Stadial in the Eastern Cordillera of Colom­
bia (South America). Quat. Sci. Rev. 12. 333-344.
Kullman. L., 1998. Non-analogous tree flora in the Scandes
Mountains, Sweden. dnring early Holocene-macrofossil evi­
dence of rapid geographic spread and response to paleocli­
mate. Boreas 27, 1 55 - 1 6 1 .
Lean, 1 . , Rind. D 1998. Climate forcing b y changing solar
radiation. J. Clim. 1 1 , 3069-3094.
Lehman, SJ Keigwin, L.D .. 1992. Sudden changes in North
Atlantic circulation during the last deglaciation. Nature 356,
757-762.
Lemcke, G Sturm, M 1 996. 5180 and trace element measure.•
.•
.•
.•
.•
.•
.•
.•
Z Yu. H.E. Wright Jr. / Earth-Science Reviews 52 (200]) 333-369
ments as proxy for the reconstruction of climate changes at
Lake Van (Turkey): preliminary results. In: Dalfes. H.N
Kukla, G., Weiss. H. ( Eds.), Third Millennium BC Climate
Change an4 Old World Collapse. NATO ASI Ser., Ser. I , vol.
49, pp. 653-678.
Leonard. E.M., 1998. Is the type-Crowfoot Moraine, Alberta.
really a Younger Dryas equivalent? Geol. Soc. Am. Bull. 30
( 7), 66, Abstracts with Programs.
Leroy, S.A.G., Zolitschka, B., Negendank, J.EW., Seret, G.,
2000. Palynological analysis in the laminated sediment of
Lake Holzmaar ( Eifel, Germany): duration of Late glacial and
Preboreal biozones. Boreas 29, 52-71.
Levesque, A.1., Mayle, F.E., Walker, I.R, Cwynar, L.c., 1993. A
previously unrecognized late-glacial cold event in eastern North
America. Nature 361, 623-626.
Levesque, A.1., Cwynar, L.c., Walker, LR, 1994. A multiproxy
investigation of late-glacial climate and vegetation change at
Pine Ridge Pond, southwest New Brunswick, Canada. Quat.
Res. 42, 316-327.
Lewis, C.F.M., Anderson, T.W., 1989. Oscillations of levels and
cool phases of the Laurentian Great Lakes caused by inflows
from glacial Lakes Agassiz and Barlow-Ojibway. J. Paleolim­
nol. 2, 99-146.
Lewis, C.F.M., Anderson, TW., 1992. Stable isotope (0 and C)
and pollen trends in eastern Lake Erie, evidence for a locally­
induced climatic reversal of Younger Dryas age in the Great
Lakes basin. Clim. Dyn. 6, 241-250.
Lewis, C.F.M., Moore, T.C., Rea, D.K., Dettman, D.L., Smith,
A.M., Mayer, L.A., 1994. Lakes of the Huron basin-their
record of runoff from the Laurentide ice-sheet. Quat. Sci. Rev.
13, 891-922.
Leyden, B.W., 1995. Evidence of the Younger Dryas in Central
America. Quat. Sci. Rev. 14, 833-840.
Lister, G.S., 1988. A 15,000-year isotopic record from Lake
Ziirich of deglaciation and climatic change in Switzerland.
Quat. Res. 29, 129-141.
Lotter, A.F., 1999. Late-glacial and Holocene vegetation history
and dynamics as shown by pollen and plant macrofossil
analyses in annually laminated sediments from Soppensee,
central Switzerland. Veg. Hist. Archaeobot. 8, 165-184.
Lotter, A.F., Eicher, U., Birks, H.J.B., Siegenthaler, U., 1992.
Late-glacial climatic oscillations as recorded in Swiss lake
sediments. J. Quat. Sci. 7, 187-204.
Lowe, 1.1., 1994. North Atlantic Seaboard Programme IGCP-253:
climate changes in areas adjacent to the North Atlantic during
the last glacial-interglacial transition. J. Quat. Sci. 9, 95-198
( Special Issue Editor).
Lowe, 1.1., NASP Members, 1995. Palaeoclimate of the North
Atlantic Seaboards during the last glacial/interglacial transi­
tion. Quat. Int. 28, 51-61.
Lowell, T.V., Larson, G.1., Hughes, J.D., Denton, G.H., 1999.
Age verification of the Lake Gribben forest bed and the
Younger Dryas advance of the Laurentide Ice Sheet. Can. J.
Earth Sci. 36, 383-393.
Luckman, B.H Osborn, G.D., 1979. Holocene glacier fluctua­
tions in the middle Canadian Rocky Mountains. Quat. Res. 11,
52-77.
.•
.•
365
Lundelius Jr., E.L., Graham, RW., Anderson, E., Guilday, J.,
Holman, J.A., Steadman, D.W., Webb, S.D., 1983. Terrestrial
vertebrate faunas. In: Potter, S.c. ( Ed.), Late-Quaternary Envi­
ronments of the United States. The Late Pleistocene, vol. I .
University of Minnesota Press, Minneapolis, MN, pp. 311353.
Maenza-Gmelch, T.E., 1997a. Vegetation, climate, and fire during
the late-glacial-Holocene transition at Spruce Pond, Hudson
Highlands, southeastern New York, USA. J. Quat. Sci. 12,
15-24.
Maenza-Gmelch, T.E., 1997b. Late-glacial-Early Holocene veg­
etation, climate, and fire at Sutherland Pond, Hudson High­
lands, southeastern New York, USA. Can. J. Bot. 75, 431-439.
Magny, M., Ruffaldi, P., 1995. Younger Dryas and early Holocene
lake-level fluctuations in the Jura Mountains, France. Boreas
24, 155-172.
Mangerud, J., Anderson, S.T., Berglund, B.E., Donner, J.1., 1974.
Quaternary stratigraphy of Norden, a proposal for terminology
and classification. Boreas 3, 109-128.
Mangerud, J., Svendsen, J.L, Astakhov, V.I., 1999. Age and
extent of the Barents and Kara ice sheets in Northern Russia.
Boreas 28, 46-80.
Marcoux, N., Richard, P.1.H., 1995. Vegetation et fluctuations
climatiques postglaciaires sur la cote septentrionale gaspesi­
enne, Quebec. Can. J. Earth Sci. 31, 79-96.
Mathewes, RW., 1973. A palynological study of postglacial
vegetation changes in the University Research Forest, south­
western British Columbia. Can. J. Bot. 51, 2085-3103.
Mathewes, RW., 1993. Evidence for Younger Dryas-age cooling
on the North Pacific coast of America. Quat. Sci. Rev. 12,
321-331.
Mathewes, RW., Heusser, L.E., Patterson, R.T., 1993. Evidence
for a Younger Dryas-like cooling event on the British Columbia
coast. Geology 21, 101-104.
Mayewski, P.A., Meeker, L.D., Whitlow, S., Twickler, M.S.,
Morrison, M.C., Bloomfield, P., Bond, G.C., Alley, R.B.,
Gow, A.1., Grootes, P.M., Meese, D.A., Ram, M., Taylor,
K.c., Wumkes, W., 1994. Changes in atmospheric circulation
and ocean ice cover over the North Atlantic during the last
41,000 years. Science 263, 1747-1751.
Mayewski, P.A., Meeker, L.D., Twickler, M.S., Whitlow, S.,
Yang, Q., Lyons, W.B., Prentice, M., 1997. Major features
and forcing of high-latitude northern hemisphere atmospheric
circulation using a 11O,000-year-long glaciochemical series. J.
Geophys. Res. 102C, 26,345-26,366.
Mayle, F.E., Cwynar, L.c., 1995. Impact of the Younger Dryas
cooling event upon lowland vegetation of Maritime Canada.
Ecol. Monogr. 65, 129-154.
Mayle, EE., Levesque, A.J., Cwynar, L.C., 1993a. Accelerator
spectrometer ages for the Younger Dryas event in Atlantic
Canada. Quat. Res. 39, 355-360.
Mayle, F.E., Levesque, AJ., Cwynar, L.C., 1993b. Alnus as an
indicator taxon of the Younger Dryas cooling in eastern North
America. Quat. Sci. Rev. 12, 295-305.
Mayle, F.E., Bell, M., Birks, H.H., Brooks, S.1., Coope, G.R.,
Lowe, 1.1., Sheldrick, C., Shijie, L., Tumey, C.S.M., Walker,
M.1.C., 1999. Climate variations in Britain during the last
z. Yu. H.E. Wright Jr. / Earth-Science Reviews 52 (2001) 333-369
366
glacial-Holocene transition ( 15.0-1 1.5 cal ka BP): comparison
with the GRIP ice-core record. J. Geol. Soc. London. 156 (II).
4 1 1-423.
McCabe. A.M Clark. P.U 1998. Ice-sheet variability around the
North Atlantic Ocean during the last deglaciation. Nature 392.
373-377.
Menounos. B.. Reasoner, M.A.. 1997. Evidence for cirque glacia­
tion in the Colorado Front Range during the Younger Dryas
Chronozone . Quat . Res. 48, 38-47.
Mikolajewics, S.H.. Crowley, TJ., Schiller, A.. Voss, R, 1997.
Modelling teleconnections between the North Atlantic and
North Pacific during the Younger Dryas.Nature 387, 384-387.
Miller, RF., 1997. Late-glacial (Allerod Younger Dryas)
Coleoptera from central Cape Breton island, Nova Scotia,
Canada. Can. J. Earth Sci. 34, 247-259.
Miller, R.F.. Morgan. A.V.. 1982. A postglacial coleopterous
assemblage from Lockport Gulf, New York. Quat. Res. 17,
258-274.
Moore, T.e., Rea, D.K., Mayer, L.A., Lewis, C.F.M., Dobson,
D.M., 1994. Seismic stratigraphy of Lake Huron-Geogian
Bay and postglacial lake level history. Can. J. Earth Sci. 3 1 ,
1606- 161 7 .
Moore Jr., T.e., Walker, e.G Rea. D.K.. Lewis, C.F.M Shane,
L.C.K.. Smith, AJ., 2000. Younger Dryas interval and out­
flow from the Laurentide ice sheet. Paleoceanography 15,
4-18.
Morgan, A.V., 1987. Late Wisconsin and early Holocene paleoen­
vironments of east-central North America based on assem­
blages of fossil Coleoptera. In: Ruddiman, W.F., Wright. H.E.
Jr. (Eds.), North America and Adjacent Oceans During the
Last Deglaciation. Geol. Soc. Am., The Geology of North
America, vol. K-3, pp. 353-370.
Morgan, A.V., 1992. Comparisons between Europe and North
America for the Younger Dryas: the insect evidence. Geol.
Assoc. Can.-Mineral. Assoc. Can. 17. A79. Programs with
Abstracts.
Morgan, A.V., Morgan, A., Ashworth, A.C., Matthews Jr., J.e.,
1983. Late Wisconsin fossil beetles in North America. In:
Potter, S.C. (Ed.), Late-Quaternary Environments of the United
States. The Late Pleistocene, vol. I . University of Minnesota
Press, Minneapolis, MN. pp. 354-363.
Mott, RJ., 1994. Wisconsinan Late glacial environmental change
in Nova Scotia: regional synthesis. 1. Quat. Sci. 9, 155- 160.
Mott, RJ., Stea, RR, 1993. Late-glacial (Allerod/Younger
Dryas) buried organic deposits, Nova Scotia, Canada. Quat.
Sci. Rev. 12, 645-657.
Mott, RJ., Grant, D.R., Stea, R, Occhietti, S., 1986. Late-glacial
climatic oscillation in Atlantic Canada equivalent to the
Allerod/Younger Dryas event. Nature 323, 247-250.
Osborn, G., Gerloff, L., 1997. Latest Pleistocene and early
Holocene fluctuations of glaciers in the Canadian and northern
American Rockies. Quat. Int. 38/39, 7-19.
Osborn, G., Clapperton, C., Davis, P.T., Rea�oner, M., Rodbell,
D.T., Seltzer, G.O., Zielinski, G., 1995. Potential glacial evi­
dence for the Younger Dryas event in the Cordillera of North
and South America. Quat. Sci. Rev. 14, 823-832.
Pennington, W., 1986. Lags in adjustment of vegetation to climate
.•
.•
.•
.•
caused by the pace of soil development: evidence from Britain.
Vegetation 67, 105- 1 18.
Peteet, D.M., 1987. Younger Dryas in North America-modeling ,
data analysis, and re-evaluation. In: Berger, W.H., Labeyrie,
L.D. (Eds.), Abrupt Climatic Change. Reidel, Dordrecht, pp.
185-193.
Peteet, D., 1995. Global Younger Dryas? Quat. Int. 28, 93- 104.
Peteet, D.M., Mann, D.H., 1994. Late-glacial vegetation, tephra,
and climatic history of southwest Kodiak Island, Alaska.
Ecoscience I, 255-267.
Peteet, D.M.. Vogel, 1.S., Nelson, D.E.. Southon, J.R., Nickmann,
RJ., Heusser, L.E., 1990. Younger Dryas climatic reversal in
northeastern USA? AMS ages for an old problem. Quat. Res.
33, 2 19-230.
Peteet. D.M., Daniels, R.A., Heusser, L.E., Vogel, J.S., Southon,
J.R, Nelson, D.E., 1993. Late- glacial pollen. macrofossils,
and fish remains in the northeastern U.S.A.: the Younger
Dryas oscillation. Quat. Sci. Rev. 12, 597-612.
Peteet, D.M., Daniels, R.A., Heusser, L.E., Vogel, J.S., Southon,
J.R, Nelson, D.E." 1994. Wisconsinan late-glacial environ­
mental change in southern New England: a regional synthesis.
J. Quat. Sci. 9, 151-154.
Peteet. D., Del Genio, A., Lo, K.K.-W., 1 997. Sensitivity of
northern hemisphere air temperatures and snow expansion to
North Pacific sea surface temperatures in the Goddard Institute
for space studies general circulation model. J. Geophys. Res.
102, 23781-2379 1 .
Porter, S.C., An, Z., 1995. Correlation between climate events in
the North Atlantic and China during the last glaciation. Nature
375, 305-308.
Ralska-Jesiewiczowa, M., Goslar, T., Madeyska, T., Starkel, L.
(Eds.), 1998. Lake Gosziaz, Central Poland. Institute of Botany,
Polish Academy of Sciences, Krakow.
Rea, D.K., Moore, T.C., Anderson, T.W., Lewis, e.F.M., Dobson,
D.M., Dettman, D.L., Smith, AJ., Mayer, L.A., I 994a. Great
Lakes paleohydrology: complex interplay of glacial meltwater.
lake levels, and sill depths. Geology 22, 1059- 1 066.
Rea, D.K., Moore Jr., T.C., Lewis, C.F.M., Mayer, L.A., Dettman,
D.L., Smith. A.L., Dobson, D.M., I 994b. Stratigraphy and
paleolimnologic record of lower Holocene sediments in north­
ern Lake Huron and Georgian Bay. Can. J. Earth Sci. 31,
1586-1605.
Reasoner, M.A., 1998. Synchronous response of late Pleistocene
to early Holocene pollen records from high-altitude sites in the
Rocky Mountains; evidence from terrestrial macrofossil based
chronologies. Geol. Soc. Am. 30 (7), 66-67, Abstracts with
Programs.
Reasoner, M.A., Huber, U.M., 1999. Postglacial palaeoenviron­
ments of the upper Bow Valley, Banff National Park, Alberta,
Canada. Quat. Sci. Rev. 18, 475-492.
Reasoner, M.A., Jodry, M.A., 2000. Rapid response of alpine
timberline vegetation to the Younger Dryas climate oscillation
in the Colorado Rocky Mountains, USA. Geology 28, 51-54.
Reasoner, M.A., Osborn, G., Rutter, N.W., 1994. Age of the
Crowfoot advance in the Canadian Rocky Mountains: a glacial
event coeval with the Younger Dryas oscillation. Geology 22,
439-442.
Z Yu, H.E. Wright Jr./ Eanh-Science Reviews 52 (200]) 333-369
Richard, PJ.H.,
1 994. Wisconsinan late-glacial environmental
change in Quebec: a regional synthesis. J. Quat. Sci. 9,
1 65- 1 70.
tory of the Allegheny Plateau and the till plains of Ohio and
Indiana. Boreas 1 6, 1 - 20.
Shane, L.C.K, Anderson, KH.,
Richard, PJ.H., Larouche, A.C., Lortie, G., 1992. Paleophyto­
geographie et paleoclimats postglaciaires dans
I' ouest du Bas­
Saint-Laurent, Quebec, Canada. Geogr. Phys. Quat. 46, 1 5 1 1 7 2.
367
1993. Intensity, gradients and
reversals in late glacial environmental change in east-central
North America. Quat. Sci. Rev. 1 2. 307-3 20.
Siegenthaler, U., Eicher. U., 1 986. Stable oxygen and carbon
isotope analyses. In: Berglund,
Rind, D., Overpeck, J., 1993. Hypothesized cause of decade-to­
century-scale climate variability: climate model results. Quat.
Sci. Rev. 1 2, 357-374.
B.E.
(Ed.),
Handbook of
Holocene Palaeoecology and Palaeohydrology. Wiley, Toronto,
pp. 407-4 2 2.
Siegenthaler, U., Eicher, U., Oeschger, H.. 1 984. Lake sediments
Rind, D., Peteet, D., Broecker, W., McIntyre, A., Ruddiman, W.,
1986. The impact of cold North Atlantic sea surface tempera­
tures on climate: implications for the Younger Dryas cooling
as continental
( a18 0
records from the glacial/post-glacial
transition. Ann. Glacio!. 5, 1 49- 1 5 2.
Sowers, T., Bender, N .. 1 995. Climate records covering the last
deglaciation. Science 269, 2 10- 2 14.
( 1 1 - 1 0 k). Clim. Dyn. 1 , 3-33.
Ritchie, J.C., Lichti-Federovich, S., 1 967. Pollen dispersal phe­
Steig, EJ., Brook, EJ., White, J.W.C., Sucher. C.M .. Bender,
nomena in arctic-subarctic Canada. Rev. Palaeobot. Palyno!. 3,
M.L., Lehman, SJ., Morse, D.L., Waddington. E.D .• Clow,
255- 266.
G.D., 1998. Synchronous climate changes in Antarctica and
Roberts. N .. Taieb, M., Barker. P.. Damnati,
B., leole, M.,
Williamson. D., 1993. Timing of the Younger Dryas event in
East Africa from lake-level changes. Nature 366, 146- 148.
Rooth, c., 1 9 8 2. Hydrology and ocean circulation. Prog. Oceanogr.
1 1 . 1 3 1 - 149.
Rouse. W.R.. 1 99 1 . Impacts of Hudson Bay on the terrestrial
climate of the Hudson Bay Lowlands. Arct. Alp. Res. 23,
24-30.
Rousseau, D.D., Preece. R.. Limondin-Lozouet. N . • 1998. British
late glacial and Holocene climatic history reconstructed from
land snail assemblages. Geology 26. 65 1 -654.
tions in the tropics: the influence of Atlantic Ocean circula­
tion. Nature 343, 607-61 2.
Stuiver. M., Grootes, P.M., 2000. GlSP2 oxygen isotope ratios.
Quat. Res. 53, 277- 284.
Stuiver, M., Grootes, P.M., Braziunas. T.F., 1995. The GISP2
al8 0
climate record of the past 1 6,500 years and the role of
sun, ocean, and volcanoes. Quat. Res.
44, 34 1 - 354.
Taylor, KC., Lamorey, G.W., Doyle, G.A., Alley. R.B., Grootes.
P.M., Mayewski, P.A., White, J.W.C., Barlow, L.K, 1993.
Ruddiman, W.F .• McIntyre. A .• 1 98 1 . The mode and mechanism
of the last deglaciation: oceanic evidence. Quat. Res.
the North Atlantic. Science 282, 9 2-95.
Street-Perrott, F.A., Perrott, R.A., 1 990. Abrupt climate fluctua­
16.
1 25- 1 34.
The "flickering" switch of late Pleistocene climate change.
Nature 36 1 , 43 2-436.
Taylor, KC., Mayewski, P.A., Alley, R.B., Brook, EJ., Gow,
Rutter. N.W., Weaver, AJ . • Rokosh, D., Fanning, A.F., Wright,
AJ., Grootes, P.M., Meese, D.A., Saltzman, E.S., Severing­
D.G., 2000. Data-model comparison of the Younger Dryas
haus, J.P., Twickler. M.S .• White. J.W.C .• Whitlow. S., Zielin­
event. Can. J. Earth Sci. 37, 8 1 1 -830.
Saarnisto. M., 1 974. The deglaciation history of the Lake Superior
region and its climatic implications. Quat. Res. 4, 3 1 6-339.
Sauer, P.E., Eglinton, T.I., Hayes, J.M., Sessions, A.L., Schim­
melmann, A.,
1 999.
ski. G.A..
1 997. The Holocene Younger Dryas transition
recorded at Summit, Greenland. Science 278. 8 25-827.
Teller. J.T., 1987. Proglacial lakes and the southern margin of the
Laurentide ice sheet. In: Ruddiman. W.F., Wright. H.E. Jr.
Compound-specific hydrogen isotope
(Eds.). North America and Adjacent Oceans during the Last
measurements of organic matter: a new paleoclimate tool and
Deglaciation. Geo!. Soc. Am., The Geology of North America.
organic material tracer. Extended Abstracts of the 1 9th Inter­
national Meeting on Organic Geochemistry, pp. 83-84.
vo!. K-3, pp. 39-69.
Thompson. L.G., Mosley-Thompson. E .. Davis. M.E .. Lin. P.-N .•
Schwert. D.P., Anderson, T.W., Morgan, A., Morgan, A.V., Kar­
Henderson. KA .• Cole-Dai. J .• Bolzan. J.F.. Liu. KB .• 1995.
row, P.F., 1985. Changes in late Quaternary vegetation and
Late glacial stage and Holocene tropical ice core records from
insect communities in southwestern Ontario. Quat. Res. 23,
205 - 2 26.
Severinghaus, J.P., Brook, EJ., 1 999. Abrupt climate change at
the end of the last glacial period inferred from trapped air in
polar ice. Science 286, 930-933.
Huascaran. Peru. Science 269, 46-50.
Van der Hammen. T .• Hooghiemstra, H ..
1995. The El Abra
Stadial. a Younger Dryas equivalent in Colombia. Quat. Sci.
Rev. 14. 841-85 1 .
Van Geel. B .• Coope. G.R., Van der Hammen. T. • 1989. Palaeoe­
Severinghaus, J.P., Sowers, T., Brook, EJ., Alley, R.B., Bender,
cology and stratigraphy of the Late glacial type section at
M.L., 1998. Timing of abrupt climate change at the end of the
Usselo (The Netherlands). Rev. Palaeobot. Palyno!. 60. 25-
Younger Dryas interval from thermally fractionated gases in
polar ice. Nature 39 1 , 1 4 1 - 1 46.
Shane, L.C.K, 1 980. Detection of a late-glacial climatic shift in
central mid-western pollen diagrams. American Quaternary
Association, 6th Biennial Meeting (Orono, Maine), Abstracts.
p. 1 7 1 .
Shane, L.C.K, 1987. Late-glacial vegetational and climatic his-
1 29.
Van Zant. K . 1 979. Late glacial and postglacial pollen and plant
macrofossils from Lake West Okoboji. northwestern Iowa.
Quat. Res. 1 2. 358-380.
Velichko. A.A .• Kononov. Y.M . • Faustova, M.A., 1 997. The last
glaciation of
4 1 , 43-5 1 .
Earth: size and volume of ice-sheets. Quat. Int.
z. Yu. H.E. Wright Jr./ Eanh-Science Reviews 52 (200 ]) 333-369
368
von Grafenstein. U .• Erlenkeuser, H., Muller, J., Kleinmann-Ei­
senmann, A., 1 992. Oxygen isotope records of benthic ostra­
cods in Bavarian lake sediments. Naturwissenschaften 79,
145-152.
von Grafenstein, U., Erlenkeuser, H., Kleinmann, H., Muller, J.,
Trimborn, P., 1 994. High-frequency climatic oscillations dur­
Wright Jr., H.E., 1 984. Sensitivity and response time of natural
systems to climatic change in the late Quaternary. Quat. Sci.
Rev. 3, 9 1 - 1 3 1 .
Wright Jr., H.E., 1989. The Amphi-Atlantic distribution of the
Younger Dryas paleoclimatic oscillation. Quat. Sci. Rev. 8,
295-306.
ing the last deglaciation as revealed by oxygen-isotope records
Yu., Z.e., 1997. Late Quaternary Paleoecology of the Southern
of benthic organisms (Amrnersee, southern Germany). J. Pale­
Niagara Escarpment, Ontario, Canada: A Multiple Proxy In­
von Grafenstein, U., Erlenkeuser, H., Muller, J., Jouzel, J.,
tion, Department of Botany University of Toronto, Toronto.
olimnol. I I , 349-357.
Johnsen, S., 1998. The cold event 8200 years ago documented
in oxygen isotope records of precipitation in Europe and
Greenland. Clim. Dyn. 14, 73-8 1 .
von Grafenstein, U., Erlenkeuser, H., Brauer, A., Jouzel, J.,
Johnsen, S.1., 1 999. A mid-European decadal isotope-climate
record from 1 5,500 to 5000 years B.P. Science 284, 1 654-
1657.
vestigation of Vegetation and Climate History. PhD Disserta­
380 pp.
Yu, Z.e., 2000. Ecosystem response to late-glacial and early-Ho­
locene climate oscillations in the Great Lakes region of North
America. Quat. Sci. Rev. 19, 1 72 1 - 1 745.
Yu, Z.C., Eicher, U., 1998. Abrupt climate oscillations during the
last deglaciation in central North America. Science 282,
2235-2238.
Waddington, J.C.B., 1 969. A stratigraphic record of the pollen
Yu, Z.C., Ito, E., 1999. Possible solar forcing of century-scale
influx to a lake in the Big Woods of Minnesota. Spec.
drought frequency in the northern Great Plains. Geology 27,
Pap.-Geol. Soc. Am. 123, 263-282.
Walker, M.J.C., 1984. Pollen analysis and Quaternary research in
Scotland. Quat. Sci. Rev. 4, 369-404.
Walker, I.R., Mott, RJ., Smol, J.P., 1 99 1 . Allerod-Younger Dryas
lake temperature from midge fossils in Atlantic Canada. Sci­
ence 253, 1 010- 1 0 1 2.
Walker, M.J.e., Bohncke, S.1.P., Coope, GR, O'Connell, M.,
Usinger, H., Verbruggen, C., 1 994. The Devensian (Weich­
selian) Late glacial in North-west Europe (Ireland, UK, North
263-266.
Yu, Z.C., McAndrews, J.H., Eicher, U., 1997. Middle Holocene
dry climate caused by change in atmospheric circulation pat­
terns: evidence from lake levels and stable isotopes. Geology
25, 25 1 -254.
Zhou, WJ., Donahue, D.1., Porter, S.C., Jull, T.A., Li, X.,
Stuiver, M., An, Z.S., Matsumoto, E., Dong, G.R., 1 996.
Variability of monsoon climate in East Asia at the end of the
last glaciation. Quat. Res. 46, 2 1 0-239.
Belgium, The Netherlands, North Germany). J. Quat. Sci. 9,
109- 1 1 8.
Watts, W.A., 1977. The Late Devensian vegetation of Ireland.
Philos. Trans. R. Soc. London, Ser. B 380, 273-293.
Zicheng Yu received his BSc in Physi­
southeastern United States. Annu. Rev. Ecol. Syst. I I , 387-
ronmental Studies ( 1 988) from Peking
Watts, W.A., 1985. Quaternary vegetation cycles. In: Edwards,
from 1988 to 1 99 1 . He obtained his
Watts, W.A., 1 980. The late Quaternary vegetation history of the
cal Geography
409.
University
(China), where he taught
second MSc
KJ., Warren, W.P. (Eds.), The Quaternary History of Ireland.
(J 985) and MSc in Envi­
(J 992)
and PhD
(J 997)
in
Academic Press, London, pp. 155- 1 85.
Botany from the University of Toronto
and palaeoclimate of the last glacial period at Lago Grande di
was on abrupt climatic changes and dif­
Watts, W.A., Allen, J.R.M., Huntley, B., 1996. Vegetation history
(Canada). The topic of his PhD research
Monticchio, southern Italy. Quat. Sci. Rev. 15, 1 33- 1 53.
ferential biological and hydrological re-
White, J.W.e., Steig, E.1., 1998. Timing is everything in a game
sponses using multiple proxy data from
of two hemispheres. Nature 394, 7 17-7 18.
lake sediments in the Great Lakes re­
Whitlock, C. , Bartlein, PJ., Watts, W.A., 1993. Vegetation his­
gion. He worked for about 1 year as a post-doctoral fellow in the
Lake, Minnesota: Evidence for Rapid Climate Change in the
(USA) on high-resolution climatic record of the last 2000 years in
North-Central United States. Spec. Pap.-Geol. Soc. Am., vol.
the northern Great Plains using stable isotopes and trace elements.
tory of Elk Lake. In: Bradbury, J.P., Dean, W.E. (Eds.), Elk
276, pp. 25 1 -274.
Willis, K.J., 1 994. The vegetational history of the Balkans. Quat.
Sci. Rev. 1 3, 769-788.
Willis, KJ., Rudner, E., Sumegi, P., 2000. The full-glacial forests
of central and southeastern Europe. Quat. Res. 53, 203-21 3 .
Wilson, S.E., Walker, I.R., Mott, RJ., Smol, J.P., 1993. Climate
and limnological changes associated with the Younger Dryas
in Atlantic Canada. Clim. Dyn. 8, 1 17 - 1 87.
Limnological Research Center at the University of Minnesota
After that, he spent 2 years as a post-doctoral fellow at the
University of Alberta (Canada) working on ecosystem modeling
of boreal forested peatlands and carbon dynamics-climate connec­
tions. Currently, he is a Research Scientist with the Climate
Change Network at the Canadian Forest Service in Edmonton,
working
on
carbon and vegetation dynamics of boreal upland and
lowland forest. His research interests are interdisciplinary and at
multiple temporal scales on vegetation succession and dynamics,
Wohlfarth, B., 1 996. The chronology of the last termination: a
past climate change and variability. ecological response to climate
review of radiocarbon-dated, high-resolution terrestrial strati­
fluctuations, carbon dynamics of northern peatlands and climatic
graphies. Quat. Sci. Rev. 1 5, 267-284.
connection, and process-based ecosystem modeling.
Z Yu, H.E. Wright Jr./Earth-Science Reviews 52 (200]) 333-369
H.E. Wright Jr. attended Harvard Uni­
versity
(AB 1939,
PhD 1943) and has
been on the faculty at the University of
Minnesota since 1 947, most recently as
Regent' s professor of Geology, Ecol­
ogy, and Botany and Director of the
Lirnnological Research Center. His re­
search expanded from arid-region geo­
morphology in New Mexico to studies
of the late-Quaternary history of land­
scapes in different climatic and geomorphic settings, including glaciation of
Minnesota, forest-fire history in Minnesota and Labrador, vegeta­
tional and climatic history of the Near East and Greece, glaciation
in the Andes of Peru and Bolivia, peatland patterns in Sweden,
stable-isotope stratigraphy of Irish lake sediments, and lake devel­
opment and vegetational history of the mountains and plains of
southwestern Siberia.
369