ARTICLES
PUBLISHED ONLINE: 27 MAY 2012 | DOI: 10.1038/NGEO1481
An aerial view of 80 years of climate-related
glacier fluctuations in southeast Greenland
Anders A. Bjørk1 *, Kurt H. Kjær1 , Niels J. Korsgaard1 , Shfaqat A. Khan2 , Kristian K. Kjeldsen1 ,
Camilla S. Andresen3 , Jason E. Box4,5 , Nicolaj K. Larsen6 and Svend Funder1
Widespread retreat of glaciers has been observed along the southeastern margin of Greenland. This retreat has been
associated with increased air and ocean temperatures. However, most observations are from the satellite era; presatellite
observations of Greenlandic glaciers are rare. Here we present a unique record that documents the frontal positions for
132 southeast Greenlandic glaciers from rediscovered historical aerial imagery beginning in the early 1930s. We combine
the historical aerial images with both early and modern satellite imagery to extract frontal variations of marine- and
land-terminating outlet glaciers, as well as local glaciers and ice caps, over the past 80 years. The images reveal a regional
response to external forcing regardless of glacier type, terminal environment and size. Furthermore, the recent retreat was
matched in its vigour during a period of warming in the 1930s with comparable increases in air temperature. We show that
many land-terminating glaciers underwent a more rapid retreat in the 1930s than in the 2000s, whereas marine-terminating
glaciers retreated more rapidly during the recent warming.
S
ince the mid 1990s, sections of the Greenland Ice Sheet
margin have been retreating significantly1,2 , leading to
glacier speedups and dynamic ice loss3–9 . Notable are
the major changes in southeast Greenland. Evidence from the
Gravity Recovery and Climate Experiment mission10–12 , radar
interferometry13 and a global positioning system14 show significant
increases in the mass-loss rate and glacier velocities in this region
since late 2003. This acceleration is partly attributed to increased
dynamic thinning triggered by rising air and ocean temperatures9,15 .
However, although the mass loss of the entire ice sheet has steadily
increased16 , glaciers along the southeastern margin decelerated and
advanced in 2006 (refs 3,5,17), suggesting episodic rather than
steady changes in frontal positions.
In situ mass-balance measurements in southeast Greenland are
rare and exist only for a single glacier over a longer timescale18 .
Consequently, frontal area and length changes of outlet glaciers
have been used implicitly to derive changes in regional mass
balance19–21 . Several studies have investigated short-term frontal
changes of glaciers on the southeast coast of Greenland and almost
all have been limited to satellite imagery19–22 . Although a few studies
have investigated sporadic aerial imagery and frontal changes in the
region on a longer timescale23,24 , none have so far investigated the
entire time span from 1931 to present.
In the early twentieth century several expeditions were launched
to east Greenland to produce new geographical maps and in many
instances to map the coastlines for the first time. Using state-ofthe-art photographic and aircraft technology, the seventh Thule
Expedition25,26 conducted a systematic survey of the southeast coast
of Greenland in 1932–1933. After the initial use the images were
classified and not generally accessible. Later, they were archived
in a citadel outside Copenhagen, and knowledge of their location
forgotten. Our rediscovery of the early twentieth-century images
Figure 1 | Historical aerial photographs from the seventh Thule
Expedition, 1933. The oblique photographs were recorded from a Heinkel
MKII hydroplane and show the Helheim Glacier (SEGL014). Images (no.
20.907–20.910) were recorded from left to right at 4,000 m elevation.
along with air photos obtained by the US military in the World
War II era provide us with a unique opportunity to observe changes
in Greenlandic glaciers at high spatial resolution from a period
where quantitative observations and measurements are absent
(Fig. 1 and Supplementary Information). Furthermore, the recent
fluctuations in the Greenland Ice Sheet mass balance underlines
that longer-term records are needed to explain a causal relationship
between climate and glacier variability in this region.
Unravelling historical imagery
We analyse the frontal behaviour of 132 glaciers along more than
600 km of the southeast Greenland coastline, between 61.5◦ N
and 66.5◦ N latitude. Combining aerial photographs (1931–1933,
1 Centre
for GeoGenetics, Natural History Museum of Denmark, University of Copenhagen, Copenhagen 1350, Denmark, 2 DTU Space — National Space
Institute, Technical University of Denmark, Department of Geodesy, Copenhagen 2100, Denmark, 3 Geological Survey of Denmark and Greenland,
Department of Marine Geology and Glaciology, Copenhagen 1350, Denmark, 4 Department of Geography, The Ohio State University, Columbus, Ohio
43210-1361, USA, 5 Byrd Polar Research Center, The Ohio State University, Columbus, Ohio 43210-1002, USA, 6 Department of Geoscience, Aarhus
University, Aarhus 8000, Denmark. *e-mail: [email protected].
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© 2012 Macmillan Publishers Limited. All rights reserved.
427
NATURE GEOSCIENCE DOI: 10.1038/NGEO1481
ARTICLES
Table 1 | Images and sources used in this study.
Year
Date
Data type
Source
Ground resolution
Number of images used
1931
1932
1933
1933
1943?
1965
1972
1981/1985
2000
2010
20 July
August
August
Late July
End of melt season
Late July
Early September–early October
Late July
August
Late July/August
Oblique aerial
Oblique aerial
Oblique aerial
Terrestrial
Vertical aerial
Satellite
Satellite
Vertical aerial
Satellite
Satellite
BAARE
Seventh Thule
Seventh Thule
Seventh Thule
USAAF/USN
Corona
Landsat 1 MSS
KMS
Landsat 7 ETM +
Landsat 7 ETM +
<60 m
<60 m
<60 m
n.a.
∼1.7 m
0.61 m
60 m
4 m (ortho)
15 m (pan)
15 m (pan)
36
9
212
4
124
28
9
311
8
9
KMS, National Danish Survey and Cadastre; USAAF/USN, United States Army Air Force/United States Navy; n.a., not applicable. The ground resolution of the oblique aerial images vary within the frame
of the image; only images within a ground resolution of 60 m or better have been used owing to the relative higher uncertainties in rectifying the oblique images. 1981/1985 vertical aerial images from
KMS were scanned at a resolution of ∼2 m. The Landsat 7 scenes have a spatial resolution of 30 m and were pan-sharpened to a resolution of 15 m using the panchromatic band 8. The exact time of
recording remains uncertain for the USAAF/USN images (see Supplementary Information); based on the snow conditions, images must have been recorded at the end of the melt season.
66° N
Gre
enl
and
Ice
She
et
38° W
Advance (m yr–1)
0¬10
10¬25
25¬50
50¬100
100¬200
200¬420
Atl
ant
ic O
cea
n
0¬10
10¬25
25¬50
50¬100
100¬200
200¬500
500¬888
62° N
0
1933¬1943
1943¬1965
1965¬1972
1972¬1981*
1981*¬2000
2000*¬2010
Retreat (m yr–1)
N
50
km
100
Figure 2 | Frontal changes of southeast Greenland glaciers. Changes are shown as rates during six observation periods from 1933 to 2010. Red circles
show retreat and green circles advance (m yr−1 ). A total of 132 glaciers are included, originating both from the ice sheet as well as local glaciers and ice
caps. The data gap in the central fjord region in the second and third period is a result of a missing 1965 image. *Note, the 17 southernmost aerial images
were recorded in 1985 and not in 1981, and frontal change rates reflect 1985 position. Background image is an Advanced Spaceborne Thermal Emission and
Reflection Radiometer Global DEM (product of the Ministry of Economy, Trade and Industry of Japan and the National Aeronautics and Space
Administration), with land and ice-sheet masks added. Error bars reflect the measuring uncertainty for each observational period.
1943, 1981–1985), terrestrial photographs (1933) and satellite
images (1965, 1972, 2000, 2010) we determine frontal changes
over a period of 80 years (Table 1). A semi-automated referencepoint method, modified from the box method20,21,27 , is used to
measure frontal fluctuations (Supplementary Information). We
differentiate between local glaciers and ice caps peripheral to the
ice sheet, and outlets of the Greenland Ice Sheet. The surveyed
region covers a wide range of different topographic settings
and ice marginal environments (Supplementary Information).
Of 36 main (>2 km wide) marine-terminating glaciers, 30 are
represented in the data set. The remaining six large outlet
glaciers could not be digitized with adequate accuracy from the
historical imagery.
Throughout the 80 years of observation, the southeast Greenland
glaciers have undergone widespread retreat, with only a few
glaciers advancing (5%) or remaining stationary (<2%; Fig. 2). The
observational period can be divided into three distinct periods of
frontal change. Two recessional events stand out, one during the
428
1930s (1933–1943) at the onset of our observations and one during
the 2000s (2000–2010). The two periods of retreat are interrupted
by a period of widespread advance from 1943 to 1972.
During our first observation period (1933–1943) most of the
glaciers retreated (Fig. 2) with typical rates of 10–50 m yr−1 and
a maximum rate of 374 m yr−1 . This retreat occurred just after a
warming period with abnormally high temperatures and during
a period with slightly decreasing temperatures and higher-thanusual accumulation rates28 . The retreat pattern is non-uniform
as a number of glaciers in the central fjord region, primarily
marine-terminating glaciers originating from ice sheets, advanced
within this period (Fig. 2). The retreat in the 2000s is more uniform
with only 5% of the 132 glaciers advancing. The highest retreat
rates observed in the study occurred in this latest period. All
glaciers retreating at rates >200 m yr−1 are large (>2 km wide)
marine-terminating outlets from the ice sheet, with Midgaard
Glacier (in the northern part of the study area) showing the largest
retreat of 887 m yr−1 .
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NATURE GEOSCIENCE DOI: 10.1038/NGEO1481
a
SST anomaly (°C)
1.5
1.0
0.5
Retreat rates
1933¬1943 < 2000¬2010
1933¬1943 = ∗2000¬2010
1933¬1943 > 2000¬2010
0
–0.5
1
0
–1
–2
b
Tasiilaq mean annual
air temperature (°C)
–1.0
c
Average retreat rate (m yr–1)
–3
c
b
Number of observations
a
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0
16
12
8
4
0
–10
¬600 ¬400 ¬200
0
200 400
Retreat rate difference (m yr¬1)
–20
(1933¬1943¬2000¬2010)
–30
–40
–50
1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 2010
Observations
Aerial photo
Satellite
Year
Figure 3 | Average frontal changes of glaciers and temperature records.
a, SST anomaly at two locations (see map to the right) during 1912–2011
from Met Office Hadley Centre observations data sets (green and purple
curve) (Supplementary Information). The SST anomaly is relative to a
1961–2000 baseline. b, The air temperature record from Tasiilaq (blue
curve). Periods of combined forcing from air and SST warming and cooling
are shaded red and blue. c, Frontal change rates of many glaciers are
averaged, hence the mid-century cooling and related advance observed in
Fig. 2 is seen as a slowdown or slight retreat. Error bars reflect the
measuring uncertainty for each observational period.
Glacial response to warming
Air temperatures in southeast Greenland have reached record
heights since continuous observations began in 1895 (ref. 29).
The temperature rise has been steady at 1.3 ◦ C per decade since
1993. However, the recent warming is not unique for southeast
Greenland (Fig. 3). An earlier warming period of 2.0 ◦ C per
decade30,31 occurred from 1919 to 1932 (early twentieth-century
warming, ECW) and was primarily dominated by spring warming,
leading to a prolonged melt season31 . The warming has been
attributed to unusual circulation patterns in the atmosphere
over the North Atlantic Ocean32 and lower insolation due to
aerosol presence33 . However, recorded annual temperatures are
0.45 ◦ C warmer in the recent decade than during the peak of
the ECW. Both warming periods share similar North Atlantic
Oscillation phases and follow the interdecadal variations and
overall increase in sea surface temperature (SST) (Fig. 3). We
therefore use the ECW as an analogue to the present and
a means to better understand glacier response and sensitivity
to external forcing.
The 1930s and 2000s retreat events were associated with both
rising air- and SSTs well above the mean (Fig. 3). These two
retreat periods are also seen as the peak calving periods in a
study of fjord sediments from Sermilik Fjord where the Helheim
Glacier terminates and here it was documented that decadal scale
variability in frontal positions is related to decadal scale changes
in both air and sea temperatures34 . Notably, our findings show
that decadal scale climate-forced glacier changes are not restricted
Figure 4 | Retreat-rate difference between the large retreat periods
1933–1943 and 2000–2010. Yellow circles indicate glaciers experiencing
faster or equal change in the 1933–1943 period in comparison with the
2000–2010 period; blue is the opposite; green circles indicate equal frontal
retreat rates (within the measuring uncertainty of ±7 m yr−1 ).
a, Land-terminating glaciers. b, Marine-terminating glaciers. c, Histogram
depicting the difference in retreat rates between the two periods.
to the large Helheim Glacier, but that most of the glaciers along
the southeast coast followed a similar retreat pattern (Fig. 4).
Of all glaciers, 35% show higher retreat rates during the 1930s
and 20% show similar retreat rates. For land-terminating glaciers
42% were faster during the 1930s and 33% similar. However,
more glaciers retreated during the 2000s. Of the seven glaciers
undergoing high retreat rates during the 2000s (>200 m yr−1
over a ten-year period), all are relatively large marine-terminating
outlet glaciers that have proved especially sensitive to changes in
ocean temperature9,15 .
Divergence in frontal behaviour between the two warm events
is observed in the central fjord region (Figs 2 and 5). Here, a large
number of primarily marine-terminating glaciers originating from
the ice sheet advanced during the early observation period. This
region is more mountainous than others and hosts glaciers that
reach the fjords through long alpine valleys. Of all the advancing
marine-terminating glaciers from the ice sheet, nine out of ten
have abundant proglacial ice mélange. In this particular region,
the fjord ice breaks up later in the season than in the rest of
the study area, suggesting that the late breakup combined with
the presence of calf ice restrain rapid glacial retreat35 . It is also
possible that the higher-than-normal accumulation in the ECW
(ref. 28) is dominating over the effect of increased temperatures
on melt rates. Moreover, some response to the early ECW may
already have occurred before the beginning of our observations
(Supplementary Information).
Mid-century cooling
As the ECW faded, a period of cooling began in the mid 1950s
that lasted until the early 1970s. The glacier response to the cooling
was an advance, primarily among marine-terminating glaciers.
Surprisingly, a large portion (60%) of our glaciers advanced, many
already at the beginning of the period (Fig. 5), whereas another 12%
were stationary during the period. This shows that the glaciers in
this region are more sensitive to climate change and react more
rapidly to cooling than indicated both by earlier studies36,37 and by
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NATURE GEOSCIENCE DOI: 10.1038/NGEO1481
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a
38° W
At
la
nti
Gr
ee
cO
nla
nd
cea
n
Ice
Sh
ee
t
66° N
dz (m) 1933¬2007
land-terminating margins
d
62° N
1933¬1943
1943¬1965
1965¬1972
1972¬1981*
1981*¬2000
2000¬2010
300
200
100
0
0
100 200 300 400 500 600
Distance north to south (km)
b
66° N
lan
dI
ce
Sh
eet
38° W
ic O
cea
n
Gr
een
Advance (m yr–1)
Atl
ant
0¬10
10¬25
25¬50
50¬100
100¬200
200¬420
500¬888
Retreat (m yr –1)
N
62° N
–20
–40
–60
–80
Marine-terminating
1930
1950
1970
1990
2010
1940
1960
1980
2000
Year
1972¬1981*
1981*¬2000
0
–20
–40
–60
–80
Land-terminating
1930
1950
1970
1990
2010
1940
1960
1980
2000
Year
2000¬2010
0
–20
–40
–60
–80
Ice-sheet glaciers
1930
1950
1970
1990
2010
1940
1960
1980
2000
Year
0
Average retreat rate (m yr –1)
0
1965¬1972
Average retreat rate (m yr –1)
1943¬1965
Average retreat rate (m yr –1)
Average retreat rate (m yr–1)
1933¬1943
c
0¬10
10¬25
25¬50
50¬100
100¬200
200¬420
50
km
100
0
–20
–40
–60
–80
Local glaciers
1930
1950
1970
1990
2010
1940
1960
1980
2000
Year
Figure 5 | A closer look at marine- and land-terminating glaciers. Frontal changes are shown as rates during six observation periods from 1933 to 2010.
Red circles show retreat and green circles advance (m yr−1 ). *Note, the 17 southernmost aerial images were recorded in 1985 and not in 1981, and frontal
change rates reflect 1985 position. a, Land-terminating glaciers. b, Marine-terminating glaciers. c, Aggregated frontal retreat rates, with measuring
uncertainty for each period. Error bars reflect the measuring uncertainty for each observational period. d, Changes in land-terminating margin elevation for
the period 1933–2007. Filled circles are ice-sheet glaciers, open circles are local glaciers and ice caps.
more recent studies investigating marine-terminating outlets from
1972 onwards21 . Exploring SST data we find that a period of colderthan-usual temperatures reached the coast of southeast Greenland
in the late 1960s (Supplementary Information). However, the
influence of cold water on the terminus of marine-terminating
outlets does not explain the entire advance as numerous landterminating glaciers advance in the period 1943–1981 (Fig. 5).
430
Hence, a shorter melt season38 and increased accumulation28
resulted in glacier growth after the ECW. Considering the temporal
resolution of our observations, it is possible that advance may
have occurred and not been documented in this data set. Such
is the case with the Mittivakkat Glacier, which advanced between
1946 and 1956 (ref. 39), and minor advances that are not detected
in this data set have also been reported in 2006 in east and
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NATURE GEOSCIENCE DOI: 10.1038/NGEO1481
southeast Greenland17,19 . These findings emphasize the fact that
marine-terminating glaciers may respond quickly to both warmer
and colder ocean temperatures9,15,40 .
Ice-marginal sensitivity to external forcing
A comparison between retreat rates for local and outlet glaciers
from the Greenland Ice Sheet shows that local glaciers show
similar retreat rates during the two warming periods, whereas
ice-sheet glacier retreat has accelerated during the latest warming
(Fig. 5). Land-terminating glaciers, most of which are of local
origin, did however retreat more rapidly after the ECW. As most
land-terminating glaciers are situated in valleys, the ablation area
becomes smaller as the terminus retreats to higher ground. From
1933 to the present (2007) some glacier fronts have been elevated
more than 250 m (Fig. 5d). This is more pronounced for local
glaciers and ice caps. The elevation change probably explains the
differences observed in retreat rate between the ECW and the recent
warming, as the initial conditions for the two retreat periods have
changed through time.
It has been argued that the east coast can be divided into two
distinct regions with regards to ice–climate response at 69◦ N,
with the southern region being more dynamic as a response to
the influence of warm Atlantic water17 . Our results show that
glaciers in the entire southeast region south of 67◦ N have reacted
synchronously to the warming events regardless of type, size
and terminal environment, indicating that the retreat observed
during the past decade5,6,14,17,19,20 is not confined to large marineterminating glaciers from the ice sheet.
The acceleration of glacial retreat observed during the past
decade is expected to continue with rising temperatures20,21 .
Climate models project continued warming through the twentyfirst century and beyond41 , and records of ocean heat content
indicate strong increases in temperature in the past few decades42 .
With Greenland temperatures deviating at present from the
ongoing temperature rise in the Northern Hemisphere, it has
been proposed that Greenland mean temperatures must warm
1.0–1.5 ◦ C above the 2007 level to be in synchronicity with the
Northern Hemisphere31 . This has been supported by the observed
temperature rise in the subsequent four years (2008–2011) and
reinforces the expectation that continued warming will occur in the
coming years. However, the recent high rate of retreat may come
to a slowdown when retreating marine-terminating glaciers reach
their grounding line and become less sensitive to the influence of
ocean temperature19,20 , or through positive or negative feedback
mechanisms relating to the cold East Greenland Coastal Current9 .
Our analysis of historical aerial imagery from the past 80 years
shows that the glaciers of southeast Greenland have responded
vigorously on a decadal scale to both warming and cooling. Major
retreat has occurred not only during the recent warming18–20 , but
also during and after the ECW, when air and SSTs were similar
to the present or slightly lower. However, the recent retreat rate
is higher for marine-terminating glaciers whereas it was higher
for land-terminating glaciers in the early twentieth century. The
asymmetric response between glacier types suggests that although
the retreat ceased and shifted to advance in response to the
mid-twentieth century cooling, the lower retreat rate of landterminating glaciers in the recent warming period may be due to
their smaller overall extent and elevated terminus altitude. These
findings are an important contribution to the sparse knowledge
of local glaciers and ice caps in Greenland, as only a few studies
so far have carried out investigations on a regional scale43,44 and
none on the southeast coast of Greenland. Although research
shows a less pronounced retreat north of the study area7,8,17,44 ,
the recent record-setting high temperatures have resulted in an
unprecedented extent of glacial retreat in southeast Greenland,
which should continue with a persevering temperature increase.
ARTICLES
Our results have implications for future estimations of sea-level rise
as retreat rates for marine-terminating glaciers are likely to increase
as temperature rises until glacier fronts reach the grounding line,
or when cold ocean currents re-establish, whereas retreat rates
for land-terminating glaciers are not likely to rise in the same
order of magnitude.
Methods
Glacier length data were obtained from terrestrial, aerial oblique and vertical
photos and satellite images. All images were rectified in digital form according to
1981/1985-orthorectified mosaics generated from a digital elevation model (DEM)
created from the 1981 and 1985 aerial images using BAE Systems SocetSet 5.5.0.
Images from 1981 and 1985 were scanned on a photogrammetric precision scanner
from negatives at a resolution of 15 µm (2 m ground resolution), images from 1931,
1932, 1933 and 1943 were retrieved from paper copies at a resolution of 600 dpi. The
main source of historical imagery is the seventh Thule Expedition (1932–1933), but
material from the British Arctic Air Route Expedition (BAARE; 1931) has been used
to fill gaps not covered by the former. Rectification of images covering each glacier
was carried out using tie-points surrounding the glacier front and subsequently
tie-points were identified in 1981/1985 orthomosaics for coregistration. Tie-points
were placed at a similar elevation to that of the glacier front, to minimize distortion
within the rectified image. The type of transformation varied according to number
of available tie-points. Uncertainties in digitization were found empirically by using
known stationary landforms within the rectified image (for example, trim lines and
tidewater marks on bedrock) and thereby calculating the standard deviation using
the 1981/1985 orthomosaics as ground truth. Equivalent rectification process and
uncertainty estimation was carried out with all digital satellite images. After the
digitization of glacier fronts, glacier lengths were measured using a glacier length
tool developed for the Environmental Science Research Institute’s ArcGIS 10.0
that divides each glacier front into points with a separation of 15 m. From a static
measuring point placed at an arbitrary position up-glacier, the mean distances to
points were calculated (see Supplementary Information). Where 1933 images were
available, 1931 and 1932 images were used and frontal changes were calculated
to the 1933 date by linear regression. For all calculations involving average values
of frontal change rates, Midgaard Glacier (SEGL011, 66◦ 260 N, 36◦ 440 W) was
discarded from the calculations owing to its extremely high retreat resulting in
an obvious skewing of the averages. Elevation changes of land-terminating fronts
were found by extracting the elevation values of the digitized 1933 fronts from the
1981/1985-DEM, whereas recent elevations were extracted from a 2007 Systéme
Pour l’Observation de la Terre Spirit DEM.
Received 21 January 2012; accepted 20 April 2012;
published online 27 May 2012
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Acknowledgements
This study could not have been possible without the aid of The National Survey and
Cadastre (KMS, Denmark) who gave access to the historical photographs from the seventh
Thule Expedition. We are also grateful to the Scott Polar Research Institute (UK), and the
Arctic Institute (Copenhagen, Denmark) who also supplied access to historical images.
A. Pedersen (MapWorks, Denmark) wrote the script for the glacier length tool. Systéme
Pour l’Observation de la Terre Spirit DEM was obtained from B. Csatho and S. Nagarajan,
Geology Department, University at Buffalo, USA. The Advanced Spaceborne Thermal
Emission and Reflection Radiometer Global DEM data were obtained through the
online data pool at the National Aeronautics and Space Administration Land Processes
Distributed Active Archive Center, United States Geological Survey /Earth Resources
Observation and Science Center, Sioux Falls, South Dakota. We thank K. L. Bird and
E. Willerslev who edited the manuscript. This work is a part of the RinkProject financially
supported by the Danish Research Council (FNU) no. 272-08-0415 and the Commission
for Scientific Research in Greenland (KVUG).
Author contributions
A.A.B. and K.H.K. designed and conducted the study, N.J.K. conducted photogrammetry,
K.K.K. undertook the geographic information system analysis, J.E.B., C.S.A. and S.A.K.
carried out climate and SST analysis. All authors contributed to the discussion and
writing of the manuscript.
Additional information
The authors declare no competing financial interests. Supplementary information
accompanies this paper on www.nature.com/naturegeoscience. Reprints and permissions
information is available online at www.nature.com/reprints. Correspondence and
requests for materials should be addressed to A.A.B.
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