RADIOCARBON
IN TIIE PACIFIC AND INDIAN
OCEANS AND ITS RELATION
TO DEEP WATER
MOVEMENTS’
G. S. Bien, N. W. Rake&raw,
University
of
California,
San
Diego,
and H. E. Sues
La
Jolla,
California
ABSTRACL-
Since 1948, carbon-14 measurements
on the bicarbonate
of ocean water samples from
the Pacific
and Indian
oceans have been carried
out at the Scripps Institution
of
Previous reports of the results of thcsc investigations
Occnnography,
I ,a Jolla, California.
The method of
have been confirmed
and amended by many recent measurements.
extracting
CO, from ocean water has been modified
and perfected
over the past years.
The most notable results of the measurements concern the 14C content of deep ocean water
which can be interpreted
unambiguously
by considering
the aging of the water during
the time of movement
from the Weddcll
Sea castward
and then northward
into the
North Pacific Ocean.
INTRODUCTION
The principles underlying the method of
dating
arc well
known.
radiocarbon
Natural carbon has an isotopic form, 14C,
with a half-lift of some 5,730 years. Carbonaccous materials formed subaerially
will orginally contain a proportion of 14C
practically equal to that in the atmosphcrc.
With time, the radioactive isotope of the
fixed carbon will decay and its relative content will indicate the clapsed time since the
material was formed from the atmosphorc.
Early determinations of the proportion of
radiocarbon in the inorganic carbon content
of seawater indicated that the results can
be accepted only as a relative measure of
the “age” of the water, because, in general,
surface water cannot be assumed to come
into complete equilibrium
with the atmosphere before sinking. Therefore, one cannot be certain about the original radiocarbon content in any subsurface sample of
seawater. Thcrc are also some tenuous assumptions necessary in taking the residence
time of the carbon as the residence time of
the water it&f.
Nevertheless, it seems
evident that the appropriately defined residcnce time of the deep water of the oceans
is of the order of hundreds of years.
Broecker et al. ( 1960), in discussing the
natural radiocarbon in the Atlantic Ocean,
L Contribution
Oceanography,
from the Scripps Institution
of
University of California,
San Diego.
have presented the results of all the prior
measurements made in the Atlantic area and
have ably discussed the problems involved
in their interpretation,
including
the influencc of such factors as the possible introduction
of “young” carbon from the
oxidation of organic matter and of “old”
carbon from the solution of sedimentary
carbonate.
The absolute age of the water requires a
more or less arb,itrary definition;
differcnces in age or residence time, however,
are in themselves significant.
Differences
in radiocarbon content in any large mass
of water may be considered from the viewpoint of mixing of the water from different
sources or of time spent by the water in
going from one place to another. Broecker
ct al. have been concerned principally with
the former alternative in the several water
masses of the Atlantic area; we have undertaken to investigate the possibilities of the
second alternative in the Pacific and Indian
oceans.
As we have already indicated
(Bien,
Rakestraw, and Suess 1960)) the International Geophysical Year afforded us an
opportunity
to obtain deep samples in a
longitudinal
section from approximately
40” S lat to 15” N long in the Pacific Ocean.
Subsequently,
similar samples were obtained in the Indian and the North Pacific
oceans, and the results from these have
R25
R26
FIG.
G. S. BIEN,
1.
Location
N. W.
RAKESTRAW,
AND
II.
E. SUESS
of stations.
zontal position and the doors were held
firmly shut by a bridle formed by the hoisting cable itself. The weight of the full
barrel and the tension of the cable were
sufficient to kept the barrel firmly shut
even when raised from the water. The
METHODS
loose lines tended to foul, however, and the
Water samplers of several designs were design was abandoned after the barrel itconstructed, all of an approximate SO-gal self was lost in the Indian Ocean.
The final design was a square barrel with
( 190-liter)
capacity.
The first of these
spring-loaded doors, the bottom one closing
operated with spring-loaded doors mounted
on a central column in the center of the downward inside the barrel. This operated
with general satisfaction but was lost in the
barrel. When cocked, the upper door raised
Indian Ocean before some minor complicaand the bottom lowered, and when tripped
off by a falling messenger, both doors tions were eliminated.
Water samples can be preserved safely
snapped shut. These proved reasonably
for a considerable time in steel drums prosatisfactory, but required frequent attention to adjust the fitting of the doors to vided with plastic liners. If closed tightly,
prevent leakage when removed from the exchange of COz with the atmosphere will
A few samples were
be insignificant.
water.
returned
in
this
way,
but the usual practice
In a subsequent design, hinged doors
opened wide and the barrel went down in was to treat the samples on shipboard,
the vertical position. When released by a removing the total CO2 and precipitating it
as insoluble carbonate, in which form it
messenger, the barrel turned into the hori-
been reported elsewhere @ien et al. 1963a,
b ) . This paper brings the study up to date
with additional results from the Pacific and
Indian oceans. Fig. 1 shows the locations
from which all samples have been obtained.
RADIOCAl1l30N
IN
THIS
PACIFIC
AND
INDIAN
R27
OCEANS
70C into the top of a stripping column
where it meets a stream of fine bubbles of
nitrogen entering the bottom of the column
through a sintcred-glass diffuser head. The
Pressure COz-free water goes to waste from the
bottom of the column while the gas stream
passes from the top and enters an absorber
bottle through a sintered-glass diffuser. The
NH40H
absorber is a l-liter Pyrex bottle containing
+
about 800 ml of concentrated
NHdOI-I
SrC12
made approximately 1 M with SrClz. Fig.
2 is a diagram of the apparatus. Flowmeters
monitor the intake and outflow rates of the
HCl
water (from 1.5 to 2.5 liter/min),
and the
rate of addition of HCl is controlled by a
\
needle valve and drop counter.
In our experience, absorption is better in
ammonia than in alkali because it can take
place in the gas phase as well as in the
liquid. The precipitation of SrC03 is preferable to BaC03 because barium salts
sometimes contain radium, which can cause
contamination
of the counting gas with
radon; strontium salts are usually much less
contaminated with radium. The carbonate
must be reduced to carbide and hydrolyzed
with water to produce CzH2, the gas used
h-N
in our counter.
2
FIG.
2. Processing apparatus.
Water enters at
Our results are expressed as ALEC; the
the rate of 1.5-2.5 liters/min,
is acidified, heated,
derivation is as follows:
and the CO% stripped by N, gas and precipitated
By definition,
as SrCOa.
A sample
#3’.4C =
--1
.
was returned to the laboratory for further
A std
processing and counting.
Let
Originally,
the preliminary
processing
PC sample =
was done in a single batch, the whole
sample was acidified in a suitable con613Cw = that of
tainer, nitrogen gas bubbled through it, and from mass spectrograph.
the CO2 absorbed from the stream in an 19th century wood, which has an overall
alkali solution. Complete recovery can re- average of -0.025. To normalize. to 19th
century wood, A’“C = 6Ww - Bl’C,,mple,
quire considerable time, however, particularly when cold water must be heated,
A14C = 1 + 6W _ 1 _ 614c - 2A13C
In the present method of continuous
I+ 2A13C
1+ 2A13C
circulation, the CO2 can be virtually com= 6l*C - 2A13C (1 +614C) ( neglecting
pletely removed from a 5O-gal ( X&liter)
higher terms ) . Inserting numerical values,
sample in as little as 90 min.
The water is pumped from a plastic
and expressing in per mill,
drum into the apparatus, and as it enters
A14c (%o) = a’“@ (%o) - ( 2ai3c + 50)
it is acidified with I-ICI at a controlled rate.
x 1 + 814C(%o)
The water passes over electrically heated
coils and issues at a temperature of 50 to
[
1,000
*
1
1
1128
C. S. BIEN,
N. W.
TAIJLE
Sample
number
--
Long
-
JJ-410
LJ-412
I,J-321
L J-320
L J-319
LJ-318
LJ-317
LJ-316
LJ-414
L J-413
LJ-417
LJ-418
LJ- 90
LJ- 93
LJ- 91
LJ- 69
L J-408
l,J- 94
L J-409
LJ- 68
L J-326
LJ-327
LJ-415
L J-325
LJ-324
LJ- 67
LJ-416
LJ-877
LJ- 57
LJ-876
LJ- 66
LJ- 63
LJ-878
LJ- 62
LJ-879
LJ-146
LJ-140
LJ-147
L J-494
LJ- 61
LJ-495
---
64”ll’S
60”12 S
58"2O'S
..--
168”58’W
171”32’ W
168”58’ II
57"34'S
55”39’ s
52"37'S
49”42’S
46"3O'S
42"43'S
42"37'S
40"35'S
40"22'S
39”33’ s
36"27'S
34"5O'S
34"04'S
144”15’ w
177”51’W
178”57’W
178”52’ W
116”
W
96”06 W
103”2O’W
132”lO’W
164”24’ W
84”lO’ W
163”09’W
135”53 w
161”54’W
30°;6'S
26"2O'S
lSO’i2’ W
160”33’W
25"OO'S
24"41'S
16"22o'S
14”29’S
ll”25’S
7"OO'S
2"08'S
0”
5"OO'N
5"OO'N
5"32'N
145”OO’ w
155” 15’ w
161”49’W
135”30’ w
117”30’ w
132”OO’W
131”27’W
138”58’W
13o"oo'w
134"Oo'w
120"05'W
7"03'N
7"OB'N
B"14'N
----
-
158”38’W
129”17’W
156”38’W
RAKESTRAW,
1.
Pacific
AND
I-I. l2. SUESS
Ocean
Date
Uepth
.- ( In- )
0
0
74:
1,400
2,100
2,944
3,825
0
0
0
0
0
0
3,500
3,500
0
3,500
0
0
0
3,350
0
0
3,500
3,560
0
0
3,450
0
0
3,473
0
0
0
4::
1,080
0
2,987
0
1.70
5.50
6.32
3.38
2.43
9
1.48
1
*
*
ri:
9.3
9.2
11.5
1.85
1.50
*
1.46
*
17.7
21.4
*
*
27.2
+
1.54
Q
$
1.58
*
26.7
1.52
%
28.0
*
27.5
7.88
4.12
*
1.48
*
34.009
34.002
34.038
34.224
*
34.766
34.372
34.277
+
*
8
34.34
34.67
*
d
34.67
d
*
*
35.05
35.103
*
34.8
35.56
*
34.65
34.88
d
34.69
9
34.68
34.69
8
34.40
*
33.50
34.67
34.63
*
34.69
*
*
+(;14
-0.5
-1.3
-2.0
-1.1
-1.4
%:
2:
<:
d
-0.7
-0.6
-2.5
-1.2
*
-1.9
*
-0.4
*
*
ti:
*
*
4:
g:
*
-1.8
*
-1.0
-1.3
*
-0.1
:!:
-1.22
-2.51
-1.81
*
-1.4
B
-120 t 20
-66 220
-63-c 6
-121~
8
-155 -L 12
-165 + 10
-167 ?I 10
-180 -I: 10
-522
7
-45 -14
-30 k 5
-35 2 5
-60 + 8
-40&B
-180 k 8
-195 + 8
-4k20
-196 ?I 8
-7 -+ 5
-38 + 8
-24 IL 10
-202-+ 10
-12 -I- 4
-3-t 20
-197 z!I 10
-2042
8
-424
19 -t- 10
-211 + 8
46 -t- 8
-312
8
-214 +- 8
242 8
-33~~ 8
612 10
-75 2 8
-1432
8
-213 ?I 8
-27 I!Z 5
-228 -+ 8
-9+3
-
collected
~-_.-
13 Fcb 1961
15 Feb 1961
7 Fcb 1961
16
1.7
19
20
8
15
17
30
3
18
5
15
7
7
9
11
Fcb
Feb
Peb
Fcb
Dee
Dee
Dee
Nov
Mar
Mar
Mar
Nov
Apr
Mar
Mar
Mar
1961
1961
1961
1961
1957
1957
1957
1957
1961
1957
1961
1957
1961
1961
1961
1961
23 Nov
12 Mar
16 Jan
7 Nov
25 Dee
26 Feh
18 vcb
19 Fcb
21 Fcb
21 Feb
27 July
1957
1961
1964
1957
1963
1958
1958
1964
1958
1964
1959
11
2,6 July
22 ‘eb
29 July
1960
1958
1960
:‘:No obsrrvation.
In translation of Ag4C results into age, WC
have used as a starting point the activity
of 19th century wood rather than an assumed activity of water at the surface. This
is purely arbitrary and does not yield an
absolute age for the water. We believe,
however, that it facilitates the comparison
of different samples.
Accordingly:
Average age of 14C= 8,033 years
(using a half-life
of 5,568 years).
Age = 8,033 In --A%!-A sample
= 18,500 log +.
sample
Setting
A sta= 1,
A sample = 1-t A’“c
and
Age = 18,500 log [‘l/( 1 -t- A’“C)
1.
-
K4DIOCARBON
IN
TIIE
L’ACIFIC
TAULE
./
Sample
number
LJ-139
LJ-137
LJ-8808
LJ-493
LJ- 60
T,J-467
LJ-468
LJ-470
LJ-476
LJ-475
LJ-473
LJ-471
LJ-474
LJ- 59
LJ-881
LJ-328
LJ- 58
LJ-882
L-J-561
LJ-883
LJ-560
LJ-1047
LJ-420
LJ-420
LJ-425
LJ-426
LJ-427
LJ-428
I,J-285
LJ-282
LJ-283
L J-284
T,J-149
LJ-150
LJ-151
LJ-152
LJ-153
LJ-154
L J-158
TAJ-559
T,J-1048
L J-1026
LJ-558
L J-557
1.
__ .-- _ - ----- --
-z-z-.
AND
Continuecl
-~~ _-. .__
8”29’ N
120”09’ w
lO”;;O’ N
10~~39’ N
11”OO’N
14”55’ N
1,
1,
,I
,I
1,
133”OO’W
155”56’W
128”31’W
133”30 w
14”;5’ N
14”58’ N
15”OO’ N
15”42’ N
19”35’N
2O”OO’ N
24”28’ N
25”OO’ N
27”ll’
N
27”21’ N
27”27’ N
o
1,
,,
1,
1346;4/ w
127”31’ w
13o”oo’w
155”22’ W
125”OO’W
126”40’ W
131”25’ E
123”OO’W
140”00’ E
155”OO’ w
150”3S w
28”;12’ N
1,
1,
139”07’ w
30”;4’ N
,,
,I
,t
1,
1,
118h2,
30”;16’
31”29’
33 “48’
34”47’
35 “00’
147”49’ E
155”OO’W
135”Ol’ w
160”20’ E
170”02’ E
N
N
N
N
N
134f”;4’ w
II
2,280
3,370
0
40:
75:
1,039
1,240
1,711
2,384
2,757
3,479
2,987
0
0
0
0
0
0
0
0
7::
1,042
2,300
3,165
3,630
538
1,607
2,468
3,518
W
:z
120
390
600
2,000
3,300
0
0
0
0
0
1.97
1.58
*
*
10.9
8
6.8
4.3
3.72
2.68
1.89
1.73
1.53
1.66
d
0
24.4
*
25.0
*
25.02
*
25.04
4.55
3.84
34.70
34.70
*
*
34.65
34.13
34.51
34.56
34.59
34.6’1
34.561
34.70
34.67
34.69
*
Q
34.69
*
34.87
*
35.00
Q
35.283
34.194
34.436
---- ___ -.-.
c;.;p
1:50
*
*
il:
iI:
19.30
15.85
13.40
6.60
5.21
2.00
1.60
x
*
*
20.4
*
34.665
34.677
34.684
34.061
34.571
34.649
34.680
33.48
33m.44
33.48
33.16
34.35
34.66
34.67
d
8
*
34.78
*
( Continued
RESULTS
All the results to date have been collected in Tables 1 and 2, with the collcction sources arranged from south to north,
in both the Pacific and Indian oceans.
Results from deep water below 3,000 m
arc plotted in Figs. 3 and 4 to show the
gradient of variation with latitude.
In the Pacific Ocean the 14C content
decreases constantly from south to north
-1.66
-0.74
8:
*
-1.5
*
*
I
*
8
*
*
;i;
-1.2
+1*.8
-0.5
d
d
$
0
*
*
*
*
*
*
*
*
a
8
+1:9
+1.0
+0.2
-1.9
-6.0
-1.6
-10.3
*
*
Q
*
d
R29
OCEANS
~--.
A”C
6W (%o)
-._- ~-
Long
Lat
INDIAN
-.
(%o)
-253 k 8
-211 AI 8
42 2 10
-27 Z!I 4
-100 -I 8
42 & 5
-100 -I- 4
-188 +- 8
-161 2 7
-207 iz 9
-207 f 8
-227 AI 9
-207 + 8
-222 + 8
67 iz 9
-12 2 10
-33 2 8
66 k 9
33 zk 9
85.7 -c- 10
64 -I- 9
137 -t- 10
23 -f- 5
-152 k 7
-190 zb 9
-225 2 10
-223 k 10
-212 It 10
-153 zk 7
-233 + 10
-222 k 11
-217 -t- 8
-13 _+ 8
-32 IL 8
-38 I!I 8
-100 -t 8
-169 + 8
-239 -L 8
-235 2 8
59 -t- 10
131 * 10
187 k 10
23 -t- 10
59 2 10
_.Date
collected
-.____--
28 July
II
23 I?cb
303 July
238 Feb
20 Jan
1,
II
II
11
11
1959
20 Jk
24 Feb
24 Feb
21 July
268 Fcb
26 Feb
7 June
27 Feb
6 June
12 Sept
20 Aug
II
II
0
II
1963
1958
1964
1960
1958
1964
1962
1964
196,2
1964
1961
15 Ju:,
13 June
13 June
14 June
14 Ott
II
11
II
II
II
II
4 June
101 Sept
7 Aug
2 June
31 May
1960
1960
1960
1960
1959
1964
1960
1958
1962
1962
1964
1964
1962
1962
on next page )
well into the northern hemisphere; thereafter the gradient seems to flatten out. This
is consistent with Knauss’ circulation pattern, later referred to. Extensive mixing
probably also talccs place.
In the Indian Ocean, the situation is
approximately similar but not so clear. 14C
decreases from south to north, though not
so regularly, with the exception of two stations in the equatorial region. Indeed, at
H30
C:. S. MEN,
N. W.
lL4KI33’I’IXAW,
TAHLE
Sample
number
LJ-540
LJ-541
T,J-542
LJ-543
LJ-544
LJ-545
LJ-547
LJ-548
L J-546
LJ-1027
LJ-538
LJ-550
T>J-551
r,J-552
If,J-553
LJ-554
LJ-555
T,J-556
I,J-549
I, J-l 046
I,J-1030
T,J-1045
T,J-429
LJ-430
LJ-431
T,J-432
T,J-435
LJ-436
T,J-439
1,J-440
LJ-1033
LJ-1031
LJ-1032
I,J-1040
LJ-1039
T,J-1038
T,J-1049
LJ-1037
LJ-1036
T,J-1034
J,J-1035
LJ-1041
LJ-1044
LJ-1042
Lat
Long
35”OO’ N
35”Ol’ N
,t
,,
1,
,,
,,
,,
15O”OO’ W
16O”OO’W
II
11
11
II
11
II
35”;;O’ N
35”02’ N
35”05 N
1,
1,
1,
,,
,,
15&m w
140”08’W
180”
W
11
11
II
II
II
35”;6’ N
36”49’ N
41OOO.9’ N
42OO9.2’ N
44”55’ N
1,
1,
,I
1,
1,
1,
17OG3’ w
155”OO’W
155”OO’W
155”02’ W
134”55’W
II
‘1
I,
11
II
II
45”;O’ N
,,
,,
,I
,I
155GO’W
II
II
II
11
47”;8.1’ N 155lbO’W
49”OO’ N
154”58’W
II
1,
,,
II
11
1,
52”;6.5’ N 155?)3.3’W
54”34’ N
155”OO’W
Depth
~ ( nl)
0
5:;
100
500
1,000
2,000
3,500
4,soo
0
0
5:
100
500
1,050
2,000
3,500
0
0
0
0
0
1,200
1,700
2,188
2,600
2,996
3,400
3,630
0
100
200
500
998
4,064
0
0
107
210
498
1,021
0
0
1.
Tt?111p.
____-(“C)
AND
E. SUESS
Continued
“$nty
0
GO
17.00
18.06
15.27
14.84
7.38
3.46
1.96
1.54
1.49
24.26
16.53
17.79
17.40
15.48
7.99
3.58
1.95
1.52
17.50
*
21.8
a:
16.70
3.0
2.08
1.80
1.65
1.58
a
1.55
15.85
7.68
7.22
3.96
3.10
8
*
11.59
4.48
3.52
3.52
2.81
*
34.35
34.49
34.51
34.48
34.00
34.30
34.59
34.68
34.69
34.716
34.30
34.80
34.76
34.68
34.06
34.28
34.59
34.66
34.69
9
34.498
9
32.756
34.306
34.567
34.615
34.645
34.625
34.635
34.679
33.031
33.382
33.905
34.00
34.354
0
0
32.654
32.865
33.687
34.106
34.393
+
11.5
32.721
--
these stations, at approximately
5” S lat,
there is evidence of upwelling.
Radiocarbon is unusually low at both stations (see
Fig. 9) and unusually high in the deep
water. As in the Pacific Ocean, the results
here arc consistent with the assumption of
slowly rising deep water in the northern
parts of the ocean.
At the northernmost station, the deepest
water has an extraordinarily
low 14C con-
II.
PC
(X”)
Date
collected
A’% (%o)
-40 -c- 10
53 -t- 10
44 -t- 9
16 -t- 9
-150 -c- 8
-150 -t- 8
-246 k 10
-226 2 10
-320 -L: 20
140 +- 12,
74 +- 10
61 + 10
59 -c 10
-22 AI 10
-46 -c 10
-184 +- 10
-213 + 10
-312 -c 10
s5 k 10
131 c 12
62 2 11
29 -+ 10
22 + 5
-189 zk 9
-230 -+ 9
-227 -+ 10
-202 2 10
-234 -+ 10
-227 k 10
-212 2 10
144 -t- 12
44-t- 11
-59 + 8
-133 + 8
-184 -+ 8
-226 -t- 8
80 + 10
114 -t- 10
67 -t- 8
-77 r!I 11
-141 k 8
-199 -t- 10
101 xk 10
122 zk 12
22 May
24 May
II
1962
1962
11 Aug
20 May
28 May
II
1964
1962
1962
26
7
13
4
21
May
Scpt
Scpt
Scpt
Sept
1962
1964
1964
1964
1961
15 Aug
II
1964
28 Aug
16 Aug
1964
1964
II
26 Aug
18 Aug
1964
1964
tent, corresponding to an age of some 2,000
years, which seems to be in regular continuation of the 14C gradient from the far
south. The layer above it, with a higher
14C activity, seems to be rising, leaving the
older water beneath it.
As we have already reported (Bien et al.
19SO), the difference in apparent age of the
deep water of the Pacific from 40” S lat to
15” N lat is of the order of 300-400 years,
l\ADIOCRRBON
IN
m
9”?
Long
__-
LJ-691
LJ-693
L J-489
LJ-404
L J-403
LJ-401
LJ-402
LJ-374
LJ-689
LJ-690
LJ-695
LJ-488
T,J-359
L J-383
LJ -369
L J-355
LJ-698
LJ-699
T,J-696
L J-697
L J-342
LJ-339
L J-392
T,J-340
LJ-486
L J-700
LJ-686
LJ-687
L J-688
LJ-684
LJ-6851
LJ-351
LJ-350
LJ-349
L J-343
L J-683
LJ-483
LJ-496
LJ-682
LJ-487
LJ-497
L J-499
51”07’ s
65”51’ E
49”29’S
42’03’ S
132G7’ E
70”45’E
39”45’S
64”Oo’ E
37”56’S
37”51’S
36”WS
87’38’ E
84’45’ E
98”41’ E
34”h’S
105”49’ E
33G8’ s
33’21’s
33”14’S
32*49’s
30”3O’S
26’54’s
96”Ol’
E
72”42’E
108”45’ E
108”39’ E
61”53’ E
58”ll’
0
3,185
0
0
100
1,000
3,000
3,400
0
4,800
0
0
0
100
1,066
3,469
0
3,430
0
4,300
0
1,000
3,050
3,987
5,52:
0
3,400
4,400
E
5,45:
23*56’S
73” 53’ E
22”OO’S
18’49’s
17”19’S
17”19’S
17”15’S
16”56’S
14”05’S
57”30’
88”33’
84”23’
57’42’
63’50’
63”50’
72”lSE
E
E
E
E
E
E
0
1,016
1,956
3,339
0
0
350
0
0
350
350
TI-II3
1’hClF’IC
o1
r?!I;*
___-
1.63
0.74
9.3
10.88
0
3.35
1.55
1.25
14.57
0.7
14.2.
ri;
15.40
*
4.47
1.17
16.64
1.50
14.90
*
18.32
5.44
1.62
1.15
18.32
0
18.66
1.37
0.58
21.84
0.93
23.86,
4.69
2.54
1.41
ii:
25.53
14.05
d
*
8
10.30
* No observation.
+ Camplcte date unavailable.
corresponding to an overall average velocity of 0.6-0.7 mm/set based on the simple
assumptions that are made. The corrcsponding velocities in the southern part of
the Indian Ocean are of the order of 02-0.3
mm/set.
Our subsequent measurements
have not changed these conclusions.
DISCUSSION
It was surprising to find the calculated
velocities so low. This is connected with
AND
Salinity
(%o)
33.903
34.71
34.339
34.430
a
34.396
34.742
34.689,
35.372
34.70
35.2
*
35.151
*
34.377
34.718
35.737
34.73
35.41
*
35.50
34.406,
*
34.703
35.50
;ii
35.584
34.720
34.688
35.56
34.70
35.472
34.418
34.818,
34.803
0
34.571
35.410
Q
*
*
34.880
INDIAN
PC
--
R31
OCEANS
(%o)
_.
Al,‘C (%o)
---
*
;i:
Q
*
*
*
*
*
d
Q
*
*
*
$
1
8
*
*
*
-56 -t- 9
-147 E!I 11
45210
-36 IL 4
-52 A 6
-120 4 6
-155 2 7
-150 + 7
10 + 12
-123 +_ 11
-26 -I 11
-22 + 8
-25 -c- 10
-35 Ik 10
-105 z!I 9
-152 -L 11
20 -t- 10
-162 + 11
-368 k 11
-115
-22 2t 912
-0:04
0.0
-0.6
*
4
d
*
%
I
d
d
*
*
a:
8
*
ii;
*
d
d
*
-95 iI 4
-178,k 8
-190 I+ 10
-15 -c- 5
-164 -F 10
-6, + 10
-168 + 10
-171 + 10
4_+ 12
-164 IL 11
-16 -I 15
-110 +_ 68
-172 2 10
-192 If: 10
37 -L 8
-7 3- G
-49 15
35 rt 8
716
-49 14
-63, zk 4
+i,
-- - -.-
(Continued
Date
collcctcd
10 Nov
19621
12 5’6n 1961
21 Dee 1960
‘1
II
II
7 Nlcjv 1962
20 Nk
1962
25 Dee 1960
29 Dee 1960
ff
II
25 N’dv 1962
22 N6v
1962
18 D:c
II
!,
1960
1 J;I-I 1961
26 Nov 1962
4 Nov 1962
II
2 N;v
1962
15 Dk
II
II
1960
31
27
29
25
5
5
2,
1962
1960
1960
1962
1960
1960
1960
.__._-
d’ct
Nov
Nov
Ott
Dee
Dee
Dee
on next
r?%sc
>
the very long residence times, which were
also surprising when they were first reported. It would be even more surprising,
however, if long residence time were not
accompanied by slow motion.
There have been efforts to explain the
low 14C activity by contamination or mixture with old carbon from some source.
This is difficult,
because mixing with
another water mass requires that the
second mass be still older, and this com-
1132
C. S. BIEN,
N. W. lXAKESTRAW,
2.
TABLE
Sample
number
LJ-681
LJ-484
L J-4,98
LJ-396
LJ-398
LJ-395
LJ-392
J, J-394
L J-679
LJ-GBO
L J-675
LJ-676
LJ-677
L J-678
LJ-1063
LJ-1066
LJ-1067
LJ-1065
T,J-1064
L J-670
LJ-672
LJ-673
L J-674
LJ-1052
LJ-1053
T,J-1054
LJ-1061
L J-1062
LJ-1055
1,J-1050
T,J-661
LJ-662
LJ-663
LJ-664
LJ-665
LJ-666
LJ-667
LJ-668
LJ-669
L J-670
LJ-1058
LJ-1057
LJ-1059
LJ-1060
AND
Continuccl
Lat
PC
13*41’s
10*31’S
10’31’ S
10*28’S
,,
,,
1,
9”i4’
I-1. E. SUESS
s
59”42
105’34’
94”SS
99’00’
E
E
E
E
56’20’ E
s&s
,,
,,
63:;7’E
5*&Y S
I,
,,
1,
55dbO’ E
s*h
s
1,
,,
7Sdb6’ E
l”l;B’ S
1*58’S
2’00’ N
2’07’ N
41’30’
49’20’
45’38’
55’04’
E
E
E
E
So;0 N
SOk
E
S*;l6’N
,,
,,
1,
1,
I,
1,
II
,,
70’37’ E
8*;3’ N
9’18’ N
lO”14’N
1,
53’b9’ E
51’03’ E
53’01’ E
I!
0
0
350
100
343
960
2,500
3,424
0
3,480
0
1,000
2,943
3,920
0
100
200
300
500
0
1,000
2,970
5,000
0
0
0
0
> 2,000
0
2,000
0
100
200
400
600
800
1,000
1,995
3,200
3,800
<2,000
0
0
>2,000
*
*
28.4
10.27
8
10.44
4.94
2.68
1.33
26.32
*
27.94
5.85
1.76
1.60
25.42
8
*
*
*
27.94
5.78
1.78
1.38
24.62
25.74
24.30
27.02
*
25.07
d
28.46
20.45
13.37
10.85
9.54
8.38
7.18
2.73
1.71
1.66
*
13.32
25.89
8
34.41
34.631
34.336
34.675
34.6,24
34.672
34.695
35.065
*
34.518
34.78
34.74
34.72
35.226
8
*
*
*
34.518
34.78
34.74
34.72
35.207
35.246
35.016
35.321
*
35.462
d
36.36,
35.51
35.20
35.17
35.12
35.08
35.05
34.80
34.73
34.73
tf:
35.113
35.837
8
pounds the problem. Solution of sedimentary carbonate has also been suggested as a
source of carbon of low activity, but the
carbonate in the upper surface of the sedimentary layer, available for solution, contains young carbon supplied continuously
from above. It would require unusual
erosional processes to bring into solution
very much of the old carbon deeper in the
sediment. Broecker et al. ( 1960) have also
-
(o/o*)
PC
31
-16
-111
-104
-182
-200
-222
-212
22
-167
-55
-180
-176
167
49
-16
-54
-68
-122
-52
-143
-154
-129
-1
23
-5
49
-191
-5
-212
-28
-68
-13
-1212
-125
-128
-143
-184
-192
-244
-145
-93
24
-190
Sate
(%o)
+ 8
2 4
r!I 6
+ 6
I+ 7
-t- 7
e 10
+ 10
?I 12
-t- 8
-c 14
-t- 10
-c- 10
k 10
-I 7
2 8
Ik 7
f 8
It 10
+ 14
+ 10
?I 10
+ 10
* 7
-+ 6
+ 10
-I 7
z!I 7
z.k 10
-I- 8
+- 14
+- 11
rk 13
11
-F- 12
-t- 11
r+ 12
2 12
?I 12
-f- 14
k 7
2 7
+ 10
-i- 7
collectccl
25
19
24
12
Ott
Ott
Dee
Nov
1962
1960
1960
1960
27 &t
1962
14 Ott
,I
1962
Ott
II
II
19621
.I.
1
.I.
1,
;
10 &t
1962
II
4
9
12
30
Aug
Aug
Aug
Aug
15 A&
6 Ott
!1
1964
1964
1964
1964
1964
1962
20 A::g 1964
18 Aug 1964
,27 Aug 1964
discussed this source and dismissed it as
unimportant.
with
Mixing
of water, contamination
other sources of carbon, oxidation
of
organic matter, or solution of fresh carbonatc-all
would result in increasing the
14C content and decreasing the residence
time or age.
The calculated velocities are an order of
mamitude
less than any previously sup-
RADIOCARBON
IN
THE
PACIFIC
AND
INDIAN
R33
OCEANS
.
18”.
.
.
-140-
.
cl
220
14”
I
.
.
.
PACIFIC
.
l
l
l.
:’
:
OCEAN
.
.
.
-160 -
.
.
-180-
I
Ocean below
posed for deep water movements. Calculations must always be checked with direct
current measurements, and few direct measurements of deep water movements have
floats
been attempted. Neutrally-buoyant
have given useful results in many cases, but
in very deep water they have not always
been satisfactory. Some unpublished results
have been reported to us of such measurements in the Indian Ocean at 2,000 m. A
casual inspection of these indicates that
while the speed may be 2 cm/set or more,
the resultant velocity vectors at nearby
stations may vary in direction by as much
as nearly 180”.
We believe that the movement of the
deep water is in a large sense random, and
that one cannot measure the time it takes
for the water to travel long distances in
terms of small-scale velocities.
For this
purpose, we believe that the differences in
residence times, which we have measured
I
5O"S
FIG. 5.
trations
I
40
I
30
I
20
.
.
.
.
---7
.
-200 -
in the Pacific
.
.
.
P
-a
FIG. 3. Carbon-14
3,000 m, vs. latitude.
.
:
:
.
.
-120
-220 -
I
-240 -
INDIAN OCEAN
-260
I
60
50
.
I
40
FIG. 4. Carbon-14
3,000 m, vs. latitude.
.
I
-III
30
LATITUDE
20
in the Indian
IO
c
0
N
IO
Ocean below
by radiocarbon dating, are more suitable,
even if only approximate.
In the general theory of deep water movement, it is recognized that there are only
two sources of deep water-in
the very
northern Atlantic Ocean (probably including the Norwegian
Sea) and in the
Weddell Sea in Antarctica.
These two
water masses not only fill the deep Atlantic
basins but also contribute,
in unknown
proportion, to the eastward drift around
the south of Africa into the Indian Ocean
and on into the Pacific Ocean. The only
source of deep water in the Indian and
Pacific oceans, therefore, is in the south.
It is generally supposed that in each
I
IO
I
0
I
J
IO"N
Oxygen consumption vs. latitude in the deep water of the Indian Ocean. Saturation concenof oxygen minus observed values, at different sigma-t surfaces, 27.78, 27.80, and 27.82 (bottom).
IX34
G. S. RIEN,
N. W. RAKESTRAW,
AND
II.
E. SUESS
-80 -
LATITUDE
FIG. 6.
Avcragc “C content below 3,000 m in zonal areas in the Pacific, Indian and Atlantic oceans.
Width of the bars indicates the average error of dctcrmination.
Values for the Atlantic
quoted from
Broecker et al.
ocean, the strongest deep movcmcnt is
along the western boundary, and Stommel’s
theory involves return movements along the
eastern boundary as well as a slow general
diffusion upward through the thermocline.
The circulation in the deep Pacific Ocean
has been discussed by Wooster and Volkmann (1960) and by Gauss (1962), who
has made use of our earlier results on 14C
age. On the basis of the temperature distribution, he suggests a general movement
of deep water northward, a little stronger in
the western basin, a slow upwelling in the
very North Pacific, and a probable widespread return in the upper layers. He is
concerned, however, with the difficulty of
explaining the transport figures according
to the generally accepted model of the
circumpolar current. In the latter connection, WC would point out that one can
calculate a zonal velocity along the edge of
the circumpolar current at least, by using
the 14C figures at three of our stations: 1) ,
51’07’ S lat, 65’51’ E long; 2), 58”2O’ S lat,
168’58’ E long; and 3), 39’33’ S lat, 84’10’
W long. The last of these is rather too far
north, but using the figures for the deep
water, one can calculate an overall velocity
If this is approximately
of 1.4 mm/set.
true, it indicates that the deep circumpolar
current moves much more slowly than herctofore supposed.
It should be observed that the 14C
measurements confirm the picture of northward movement of deep water in both
oceans, without any indication of a return
southward in the eastern part of the ocean,
as has been suggested. Gauss’ theory of
slow rise in the north, and Stommel’s model
of general upward diffusion through the
thermocline are both consistent with our
results.
The calculation of overall velocities from
the differcnccs in radiocarbon age assumes,
of course, that the direction of motion is in
the direction of decreasing 14C content.
This is from south to north, and there is no
question of this being the direction in
which the deep water moves in the Pacific
Ocean. Knauss has clearly shown this from
the distribution of temperature. A similar
analysis of the Indian Ocean has not yet
been made, but there seems to be little
doubt of its similarity.
The gradient of oxygen consumption has
also been used to indicate the direction of
water movement, and Fig. 5 shows the
calculated values of oxygen consumption
RADIOCARBON
IN
TIIE
PACIFIC
AND
INDIAN
R35
OCEANS
-300
0
1000
PACIFIC OCEAN
E
.
2000
iz
W
a
3000
0 50020'S-l69"E
x 35°05'N-1800
x 44%'N-134'56'W
0 35"01'N-160"W
0 30°N-l180W
v 28°12'N-139"W
A 14'55'N-134"W
A
27"27'N-150"35'W
v 7f"N-120“W
4000
5000
FTG. 7.
Vertical
profiles
of A”C
at stations
in the Pacific
at a number of stations in the Indian Ocean
plotted against latitude. Increase of oxygen
consumption is a clear indication of northerly movement.
To treat our results in accordance with
the general model of deep water circulation, the Pacific and Indian oceans were
divided into zonal areas: below 40” S lat;
from 40” S lat to the equator; from the
equator to 30” N lat; and beyond 30” N lat
( in the Pacific Ocean only ) . All the values
for j4C in each of these areas below 3,000 m
were averaged and the results are shown in
Fig. 6 In similar fashion, the Atlantic
Ocean was divided into zonal areas and the
deep water values given by Broecker et al.
were averaged. j4C activity in the deep
water decreases from south to north in both
the Pacific and Indian oceans and from
north to south in the Atlantic Ocean, approaching a common value where the circulation model postulates continuity
bc-
Ocean.
tween the South Atlantic
oceans.
VERTICAL
and the Indian
DISTRIBUTION
Figs. 7 and 8 extend the data that we
reported previously on the vertical distribution of 14C. At any one station, radiocarbon
is relatively
constant with depth below
2,000 m within a range of 210%. There are
a few notable exceptions, particularly
at
two stations where activity is abnormally
low at the lowest depth. This seems to
suggest a source of “dead” carbon from
the bottom. We have already dismissed the
possibility of solution of sedimentary carbonate, but it is conceivab,lc that local
volcanic activity
might be responsible.
However, we believe that a more likely
explanation is the one already given. Both
these stations are in the northern parts of
the Pacific and Indian oceans, respectively,
where slowly rising deep water could leave
the decpcst and oldest water behind.
R36
G. S. BIIZN,
N. W.
RAKI;‘,STRAW,
AND
II.
13. SUESS
Om
1000
‘2
INDIAN
OCEAN
2000
E
I
$:
2
0
0 5"21'S-75"06'E
V
A 5O35'S- 63'47'E
X
0
8"16'N -70"37'E
A
3000
0
‘-?
I
I
.a. t
: I
:.I
S
9
Ii
Ii
I .
, i
I :
I :
I i
A \
I
’ 6..
I
**..
I
.*..
I
...*
‘...
I
I
“0
4000
d
5000
FtG.
I
I
8.
Vertical
I
profiles
of Al’C:
I
at stations
in the
The concentration gradients in the upper
parts of these profiles may be important in
interpreting mixing phenomena and the exchange with the atmosphere.
RADT.OCARBON
IN THE
SURFACE
Fig. 9 shows values for 14C in surface
water in the Pacific and Indian oceans,
plotted against latitude for different years
from 1958 to 1964. Two points are significant: the decrease in 14C from north to
south, with extremely low values in the far
south; and the general increase of ‘“C at all
latitudes from 1955 to 1964. The overall
increase is, of course, the result of artificial
nuclear activity, with greater effect in the
northern hemisphere. The very low 14C
values in the high southern latitudes remain
relatively unaffected.
As reported before,
these doubtless result from upwelling
of
I
Indian
I
I
Ocean.
deep water and its failure to come into
equmbrium with the atmosphere. Future
observations, cxtcnded over several more
years, will eventually make it possible to
deduct quantitative
data for the rates of
exchange and mixing that determine the
observed 14C concentrations on the surface
of the oceans.
ACKNOWLEDGMENT
WC gratefully
acknowledge
help, at
various stages of the project, from Warren
S. Wooster, John A. Knauss, and Joseph L.
Reid, Jr. Ship operations and the collection
of samples were completed with the support of Atomic Energy Commission Contract AT ( ll-l )-34, Project No. 74. Radiowere
financed
measurements
carbon
through a National Science Foundation
Grant.
RADIOCARl3ON
IN
THE
PACIFIC
AND
INDIAN
R37
OCEANS
n ‘“c
40 -
-40
I
-60
I
-20
I
30 20 -
+
X
X
IO +
N
LLI
a
-
IO
x
N
0
oS
=
F:
Q
-I
X
- 20
0
0
0
0
-0
S
+
IO-
0
X
20 X
-
a
- 20
0
A
IO
.O
X
X
XA
0
0
t 58-59
30 -
- 30
X 60
A61
40 -
- 40
@62
064
50 60LaAI
fi
-60
I
-40
I
-20
I
0
I
+20
I
t40
I
+60
- 50
I
t80
160
4 14c
9. Carbon-14
3958 to 1964.
FIG.
13rm,
-
in tho surface
REFERENCES
G. S., N. W. RAKESTHAW,
of the Pacific
AND H. IX. SUESS.
1960.
Radiocarbon
concentration
in Pacific
Ocean water. Tellus, 12: 436-443.
-,
AND -.
1963a. Radiocnrbob dating of deep water of the Pacific and
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dating, p. 1591173.
Intern. Atomic Energy Agency, Vienna.
AND -.
1963b.
Natural
ra&ocarbon’ in the Pacific and Indian Oceans.
Nuclear Sci. Ser. Rcpt. No. 38, p. 152-160.
and Indian
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and in years from
Publ. 1075, NAS-NRC,
Washington,
D.C.
~OECKJCR, W. S., R. GERARD, M. EWING, AND
B. C. IIECZEN.
1960. Natural radiocarbon in
the Atlantic
Occnn. J. Gcophys.
Rcs., 65:
2903-2931.
KNAUSS, J. A. 1962. On some aspects of the deep
circulation
of the Pacific.
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67:
3942-3954.
WOOSTER, W. S., AND G. II. VOLKMANN.
1960.
Indications
of deep Pacific circulation
from
the distribution
of properties
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