Marine Chemistry, 35 (1991) 137-150Elsevier Science Publishers B.V., Amsterdam

3He and chlorofluorocarbons (CFC) in theSouthern Ocean: tracers of water masses

137

P. Jean-Baptiste", F. Mantisi?', L. Memery-" and D. Jamous"aLaboratoire de Geochimie Isotopique, DPhG/LGI- CEA/Saclay, 9JJ9J - Gil/YvetteCedex, France"Laboratoire de Physique et Chimie Marines, LPCM- Universite Paris 6, 75252 - Paris Cedex05,

FranceCLaboratoire d'Oceanographie Dynamiqueet de Climatologie, LODyC- Universite Paris 6,

75252- Paris Cedex05,France

(Received 18September 1990, accepted 22 March 1991 )

ABSTRACT

Jean-Baptiste, P., Mantisi, F., Mernery, L. and Jamous, D" 1991. 3He and chlorofluorocarbons (CFC)in the Southern Ocean: tracers of water masses. Mar. Chem., 35: 137-150.

The distribution of 3He across the Southern Ocean is depicted on the basis of a meridional sectionbetween Antarctica and South Africa measured during the INDIGO-3 survey (1988). A core of (53Hevalues above 10% is observed south of the Polar Front, associated with very low CFC concentrations.This 3He enriched layer is documented from the GEOSECS and INDIGO 3He data in the SouthernOcean. It is found at a density level around 0"0=27.8 in all the waters close to Antarctica (i.e. south of50·S). Its zonal distribution suggests that it is likely that it originates from the central/eastern Pacific.Hence, it provides an indication of the deep Pacific waters in the Antarctic Circumpolar Current,which are not easily detectable from the standard hydrographic parameters.

INTRODUCTION

3He is the lighter and less abundant helium isotope. The atmospheric 3He/4He ratio is 1.38X 10-6 (Clarke et al., 1976). In the ocean interior, 3Heshowscharacteristic excesses above the solubility equilibrium. These excesses areexpressed in the t5 notation, where t53He is the per cent deviation of the iso­topic ratio of the sample (R s ) from the atmospheric ratio (Ra ) :

t53He=(~: -1)X 100%

In the deep ocean, 3He excesses above solubility equilibrium with the at­mosphere originate from the mantle 3Hewhich is released mostly through thehydrothermal circulation that occurs at mid-ocean ridge spreading centres

'Present address: ATOCHEM-CAL, 95 rue Danton, 92300 - Levallois-Perret, France.

0304-4203/91/$03.50 © 1991 Elsevier Science Publishers B.V. All rights reserved.

138 P. JEAN·BAPTISTE ET AL.

(Clarke et al., 1969;Craig and Lupton, 1981). In the upper layers ofthe ocean,3He is produced by the in situ decay of tritium. This 3He component cancreate characteristic 153He anomalies within the thermocline of up to severalper cent, especially in northern regions where artificial tritium fallout in­creased the natural tritium concentrations of ocean surface waters by abouttwo orders of magnitude during the 1960s. However, this 3He in situ produc­tion is negligible in the deep ocean, especially in the southern hemispherewhere the bomb tritium concentrations are relatively low.

Hence, the global 3He cycle is basically characterized by a continuous de­gassing of the mantle through the seafloor, which mostly takes place at mid­ocean ridges. This 3He is transferred to the atmosphere at the atmosphere­ocean boundary through the oceanic circulation and the oceanic ventilationprocesses. There, the oceanic 3He excess is reset to zero by gas exchange withthe atmosphere. The residence time of 3He in the atmosphere is of the orderofseveral million years (Kockarts and Nicolet, 1962). This figure is very highcompared with the oceanic residence time of 3He, which is of the order of afew hundred years (i.e. the turnover time of the deep world ocean) (StuiveretaI.,1983).

As one might expect, the 3He enrichment in the deep ocean varies with thescale of the hydrothermal activity and the efficiency of the deep ocean venti­lation in the oceanic basins. Hence, the 3He values for the three main deepoceans which exchange with the Southern Ocean show marked contrasts: Pa­cific deep waters are 3Herich as a result of the strength of the primordial lHeinput, which occurs mainly on the East Pacific Rise (153He values above 40%are observed in the open ocean at some distance from the ridge crest; Luptonand Craig, 1981) but also in the western Pacific. The Indian Ocean also shows3He excesses, although to a lesser extent (Jamous et al., 1991). Conversely,the Atlantic deep ocean is poor in 3He, with maximum 15 3He values in thedeep water not exceeding a few per cent (Jenkins and Clarke, 1976). This isdue to the shorter turnover time of the Atlantic and its efficient ventilation inthe northern and southern polar regions.

Becauseof these different values, 3Heis a potential tracer ofthe water massesand mixing processes in the Southern Ocean.

The present study deals with the 3He distribution in the Southern Oceanobtained from the GEOSECS survey in the 1970s (Ostlund et al., 1987), withspecial emphasis on the Indian Antarctic sector where our INDIGO-3 heliumdata are now available (Poisson et al., 1990). CFC measurements from theINDIGO-3 cruise (Poisson et al., 1990) are used as a second independenttracer of the origin and age of the water masses.

INDIGO·3 SOUTHERN OCEAN SECTION: HYDROGRAPHY AND TRACER DATA

Seawater samples were collected by means of a rosette system fitted with12 1 Niskin bottles and a Neil Brown Mark III conductivity-temperature-

'He AND CHLOROFLUOROCARBONS IN THE SOUTHERN OCEAN 139

depth (CTD) instrument (Gamberoni et al., 1990). Water samples weresealed in copper tubing and returned to the laboratory for helium isotopeanalysis. The procedure for measuring the helium isotopes was basically thatdeveloped by Clarke et al. (1976). Experimental methods and procedureshave been described by Jean-Baptiste et al. (1988). The uncertainty in the()3He is ±0.3%. Seawater for CFC analysis was transferred into 100 em" sy­ringes. The analysis was performed on board by gas stripping, cryogenictrap­ping and gas chromatography, following a method developed by Bullister andWeiss (1988). Details of the analytical techniques have been given by Man­tisi et al. (1991 ). The typical relative standard deviation for analysis of CFC­11 in surface waters is 2%, with a detection limit of about 0.01 pmol kg- I.

8-Sdata

During the INDIGO-3 cruise (January-February 1987) a meridional sec­tion was completed across the Antarctic Circumpolar Current (ACC). Thissection, shown in Fig. 1a, extends from Antarctica (65 °S) to the limit of thesouth African continent through the main fronts of the Southern Ocean(Nowlin and Klinck, 1986). These fronts are easily noticeable from the ab­rupt changes affecting the isolines of salinity and temperature of the 8 and Svertical sections (Figs. 2a and 2b). Within the water column, 8-S character­istics show major changes across these fronts.

The southernmost stations (Stations 87 and 88) exhibit the typical 8-Sdiagram of stations situated south of the Polar Front, during the austral sum­mer (Fig. 3a). In the first 100 m, one finds a core of very cold water (WinterWater), near the freezing point (8== -1.6°C at 70 m), overlaid by less coldsurface water (Summer Surface Water) which warms up during summer(8= 1.05°C). Immediately below, the 8-S profile indicates the strong influ­ence of warmer and saltier Circumpolar Deep Water (CDW) (Jacobs andGeorgi, 1977). Its salinity core is situated at around 500 m depth, 100 mbelow its temperature maximum. In the deep layers (depths greater than 3000m), the Antarctic Bottom Water (AABW) is observed; this has a high den­sity, around 27.86.

Stations 89-94 (Fig. 3b) are located in a region not covered by ice duringwinter. They basically have the same hydrographic structure, with three well­distinguished water masses. However, the temperature minimum vanishesand the surface and subsurface layers become warmer towards the north, withsurface temperatures well above O°C: 2.90°C<8surf.<4.02°C and-0.33 °C< 8subsurf. < a.73°C.

Stations 95 and 96 are located in the subantarctic region, north of the PolarFront. The surface temperature gradient steepens and the 8-S structure be­comes more complex with the appearance ofthe salinity minimum typical ofthe Antarctic Intermediate Water (AAIW) (Fig. 3c).

140

(a)

322

•

..........j.....•. ...

•' 82 •

~ /, / ~ - y - - -

' " . . . . . .. ~60.(j· ·

• .282

ANTARCTICA

P. JEAN-BAPTISTE ET AL.

(b)

.. .......~ -50.cr ·~···

• IfFig. I. Locations of the INDIGO-3 section (a) and the GEOSECS/INDIGO stations consid­ered in the present study (south of40 0S) (b).

)He AND CHLOROFLUOROCARBONS IN THE SOUTHERN OCEAN 141

(a) POTENTIAL TEMPERATURE ( • C)

~ia hvl tS 96 980

-100 ·100

-200 ·200

·300 ·300

·400 ·400-500 ·500

S·600 ·600

::r:: -700 <, ·700~ ·800 ·800P<rtl ·900 '0. ·900o

·1000 ·1000

-1100 ·1100

·1200 ·1200

·1300 ·1300

-1400 ·1400

· 1500 · 1500·70 ·65 ·60 ·55 ·50 ·45 -40 ·35

stanons 87 88 89 90 994 95 96 970,0_·-1- 0

-500 \)~ ·500

·1000 · 1000

· 1500 ·1500

~ ·2000 ·2000S

·2500 ·2500::r::

·3000 ·3000E;P<~ ·3500 ·3500Cl

·4000 ·4000

,4500 ·4500

·500 0 ·5000

·5500 ·5500

·6000 ·6000-70 -65 .60 ·55 -50 ·45 -40 -35

LATI TUDE ( . South)

Stations 97-99, situated north of the Subtropical Convergence, also displaya typical e-s profile which shows the influence of four main water masses:the central waters on the top, then the AAIW. At greater depths(27.80<0"0<27 .82), one observes a water mass the characteristics of whichoriginate from the East Atlantic deep waters, with its typical salinity maxi­mum centered around 3000 m depth. Below 4000 m, the AABW is observed(Fig . 3d).

-40

P. JEAN-BAPTISTE ET AL.

-45-50

SALINITY

-55-50

-65 -50

87

-65

142

(b)

stations

-100

-200

-300

-400

....... -500

a -600

-700::r::

-8008~ -900r.x:1Cl -1000

-1100

-1200

·1300

-1400

·1500-70

stations

-500

-1000

-1500

....... 2000a-2500

::r::30008

~r.x:1 35000

4000

-4500

5000

·5500

-6000·70

LATITUDE ('South)

Fig. 2. (a)Temperature section across the Antarctic Circumpolar Current (INDIGO-3 cruise;Gamberoni et aI., 1990). (b) Salinity (conductivity-temperature-depth (CTD» section acrossthe Antarctic Circumpolar Current (lNDIGO-3 cruise; Gamberoni et al., 1990).

The CFC section

The CFC-ll distribution along the meridional INDIGO-3 section gives di­rect information on the penetration of anthropogenic atmospheric gases inthe Antarctic region and displays the main features of the Southern Ocean

'He AND CHLOROFLUOROCARBONS IN THE SOUTHERN OCEAN 143

33.5 34,0 34.5 35.02:>

35.5 36.0 33.5 34.0 34.5 35,0 35.5 36.025

..............., .........

20+-----1-----1---+-.""..""""'--=.-+2ot---+----II------+~......-""+_--=--+

..............,........

.. ...........

.,.. ~.

....

,,"I>< 15+..--:..,..,..-""-+----o"'..--+----,.t~--j---.-'''---+

L+,.-...."""'~+---'7""+-...".."'--:t-'---",.-"f-'7"""---+~H..:HE-i:z;I><

~

(a) (b)

5-'------'----'------'----'-----'- 5-'--_--'-__-'- -'--_--'-__-'-

SALINITY SALINITY

25,..---,.---.,---,..----,---.,-

i./ ./

Cd)

..',,' ,•...

10 ...,.•.'"

15 ...."

20t---+---f---+-:,.""..."9r.;;;;---=--+.p'"

.>" •• ".

(e)

U 20

f;l 15+---:,.....ec'-j--,.,...--+--'-----",f-'"'---j--".-."--+

11Ot-7-""-+-'""7'"+---"""""-+"""--~"f'-::,-",,"-+~H

~

~ /. /.OH=---j=--';=--f-A=--t---+---+

J~

5-'-----'----'------'----'--- 5-'--_---l__-'-__-'--_--l.__--.1.

33.5 34.0 34.5 35,0 35,5 36.0 33.5 34.0 34.5 35.0 35.5 36.0

Fig. 3. Main aspects of the temperature-salinity plots across the Antarctic Circumpolar Current(Gamberoni et a!., 1990). (a) Station 87, south of the Polar Front; (b) Station 93, close to thePolar Front; (c) Station 96, in the Subantarctic Zone; (d) Station 98, north of the SubtropicalConvergence.

circulation (Fig. 4): a low CFC penetration mainly a result of the upwellingof the CDW, south of 50 0S, which acts as a barrier against the penetration ofthe atmospheric anthropogenic compounds; high CFC-ll values at interme­diate levels, tracing the downwelling of the AAIW, north of 500S; and at depth,slightly increasing CFC-ll concentrations, which represent the signature of

144 P. JEAN-BAPTISTE ET AL.

CFC-ll (prnoles/kg)

stations

or--'=:f:::::::::::;$==:::~r---=;q=:4~4~It--r,-r::r1

60 55 45 40 35

3540455560

D~'/'.3.03.

. .: : 0.1-----~ ;-;::,~~~~~~~~~: C_--,:,--_-0.\. •

65

1000

5·)00

6000 +-,-,---.­70

4000

g 2000

LATITUDE ('South)

Fig. 4. CFC-Il section across the Antarctic Circumpolar Current (lNDIGO-3 cruise). (Thecontour unit is proal kg-I).

the AABWand give information on ventilation processes and deep water for­mation in the Antarctic zone that contains the transient CFC distribution.

The 3He section

The most striking pattern immediately noticeable on the 3He contoursacross the Indian sector of the ACC (Fig. 5) is a spur of (PHe values above10%. This 3He core extends from the stations close to Antarctica to the Polar

'He AND CHLOROFLUOROCARBONS IN THE SOUTHERN OCEAN 145

Del ta 3 He (%)

stations97

405060

.$ 2.~ • • 0.0~-----1

65

.10'0~~'2.$'

~• Xl.O •. . ---- .

• ---- 10.0 • : '::"':7.;;:::::::::=.-1. .:~.

• '~7'~~------

150070

0

1000

2000

~

~

3000:r::E-iPo<~c 4000

5000

600070

LATITUDE ('South)

Fig. 5. (PRe section across the Antarctic Circumpolar Current (INDlGO-3 cruise).

Front. North of this latitude, the (PHe signal is diluted by waters influencedby the North Atlantic Deep Water (NADW), which is poor in 3He, and the(PHe values fall below 10%. The 3He maximum is centred around 1500 mdepth at 50 0S

((J(J';::! 27.76). Further south, this maximum becomes shalloweras a result of the rising of the isopycnals toward the Antarctic Divergence.

In the deeper layers, the (PHe values decrease monotonically (o3He~ 6%)because of the imprint of the AABW,which has been ventilated more recently.

A similar 3He pattern is also observable in the Atlantic (Jenkins and Clarke,1976) and Pacific (Ostlund et al., 1987) sectors on the GEOSECS sections,

146 P. JEAN-BAPTISTE ET AL.

as well as in the 3He profiles from the German cruises ANT II and III in thesouthern Drake Passage (Schlosser et al., 1987, 1988). Hence, it is a clearzonal feature that develops throughout the ACC at a density level close to(Je=27.8.

DISCUSSION

The 3Hecore depicted above is located at a level close to the salinity maxi­mum of the CDW. As this salinity maximum basically originates from theNADW, a water mass with a low (PRe, the existence of this 3He maximum ispuzzling at first sight.

From the CFC section however, we note that it is located in a region of verylow CFC concentrations (close to the detection limit), which indicates thatthis water mass is fairly old. This CFC minimum also occurs in the Atlanticsector in the AJAX section (Warner, 1988) and seems to be a zonal feature.

The 3He maximum may be indicative of the Pacific or Indian Ocean deepwaters, where t53R e values well above 10%can be found. A second possibility,however, would be a 'local' origin as a result of some hydrothermal activity

"II III II11111 N.... e

I ~~N I "lljJ"IIC1U IIIII 11111 lDlII""""

27.7 1515 l' ... H HHHH~l'

~:I 8

II

1(3 CJ:w

~rn

\ . Z\ '~4

I (f)>---4

"- --l27.8

~:-<

""'~

\ '-J\

~

8i

--27.9 -16'3 -12~ -8" -4'3 '3 4'3 Be 121i' 16ePacific I Atlantic Indian Pacific

LONGITUDEFig. 6. Zonal §3He contours vs. Ue around Antarctica. The data considered in this figure arefrom the GEOSECSjINDIGO stations located south of 400S and shown in Fig. I.

-'HeAND CHLOROFLUOROCARBONSIN TH E SOUTHERN OCEAN 147

34.1 34.3

SALINITY34.5 34.7 34.9

8

,....N"'6enIOJ

:r: 4o

-+l.......

OJo 2

8

Fig. 7. Temperature-salinity and o3He- salinity plots at GEOSECS Station 67 (Atlantic sector).Numbers indicate depths ( in meters) .

on the seafloor. Some indications oeHe injection from back-arc rifting have,in fact , been reported in the Bransfield Strait by Schlosser et al. (1988). Al­though this process cannot be totally ruled out, the shape of the 3Re zonaldistribution (see discussion below) and the correlation with low CFC valuesare more consistent with the fir st hypothesis.

The 3He contours vs flo of the available 3Re data south of 40°S all aroundAntarctica (see Fig. 1b) are , indeed, very helpful in differentiating the poten­tial Pacific and Indian Ocean contributions. As shown in Fig. 6, the 3Re val­ues strongly suggest a Pacific origin, as already mentioned by Jenkins andClarke ( 1976 ): the highest (P He values «PHe>20%) are found at GEO­SECS Stat ion 322 in the central part of the Pacific sector (no data are avail­able at those latitudes in the eastern Pacific where one could expect even highervalues ) . The second-highest set of values is found in the southern Drake Pas­sage «P He > 14% at GEOSECS Station 78) and in the southern Atlantic sec­tor (G EOSECS Station 89). This is consistent with an inflow of Pacific 3He­enriched waters in the ACe.

These waters may enter the ACC in the central/eastern part of the Pacificsector (GEOSECS Stations 282,287 and 290 in the western Pacific show nohigh JHe values ) . On their way to the east, these Pacific waters are kept in thesouthern part of the ACC as they are being diluted with waters less enrichedin 3He located more to the north; in particular, around this density level, theNADW, as mentioned at the beginning of the discussion. As an example, this

148 P. JEAN-BAPTISTE ET AL.

-1

TEMPERATURE (OC)

312 3

---l. .-l.l L.- ..l--. ....I-_-'

oro~

et­a:::r:rnI

w

NIIDW

C-:=:J

I

Pac i fic deepwa t e rs

Central Pacificstation G322 ___

Drake Pas s ages t .G78 A

A

0a > 27 .7

5

15

1~

2~

Pa c i fic deepwaters

15

1~

5

~4.3 34.5 34.7

SALINITY

Nil OW

c:=:::J

34.9

of1lI-'

et­o:cfDI

W

Fig. 8. (PHe-temperature and o3He- salinity diagrams (Southern Ocean GEOSECS and IN­DIGO stations, ao> 27.7). The letters A, I and P indicate stations from the Atlantic , Indian andPacific Ocean sectors , respectively. Data inside the dashed square correspond to the 3He maxi­mum in the Southern Ocean (o 3He> 10%).

'He AND CHLOROFLUOROCARBONS IN THE SOUTHERN OCEAN 149

dilution is particularly easily noticeable in the 3He-salinity diagram at GEO­SECS Station 67 in the Atlantic sector (Fig. 7), where the highest salinityvalues, characterizing the NADW imprint, are associated with a decrease ofc)3He.

The Pacific component is again apparent on the 3He-temperature and 3He­salinity diagrams of Fig. 8. The other water masses that may contribute to themixing are also indicated. These diagrams suggest that the 3He core that wehave documented is basically a three-component mixture: Pacific deep waters(B';:;;,1.5-1.6°C, S:=:::34.68 and (PHe:=:::20%), Atlantic deep waters, whosecharacteristics in the South Atlantic (300S) are in the range B';:;;,2.4-3.0°C,S';:;;, 34.86-34.93 and (PHe';:;;, 2%, and the more recently ventilated AntarcticBottom Water ((J';:;;, -0.5 to -0.8°C, S:=:::34.65, 63He:=:::3-4%). The data onthe left of the two diagrams (low temperature and salinity, low (PHe) corre­spond to subsurface waters of stations close to the Antarctic continent. Ac­cording to the CFC data (Mantisi et al., 1991), these waters may not contrib­ute significantly to the mixing.

CONCLUSION

As the 63He variations are relatively small (a few per cent most of the time)compared with the analytical accuracy of the whole data set (approximately1%), and because of the poor spatial resolution of the 3He measurements, adetailed study of the 3He distribution in the ACC is a very problematic un­dertaking, which is beyond the scope of this short paper. However, this pre­liminary analysis of the deep waters of the Southern Ocean, using 3He,stressesthe potential contribution of this tracer, in addition to the usual hydrographicparameters, to the study of the distribution and mixing of water masses in theACC.

REFERENCES

Bullister, J.L. and Weiss, R.F., 1988. Determination of CChF and CCI2F2 in seawater and air.Deep-Sea Res., 35(5): 839-854.

Clarke, W.B., Beg, M.A. and Craig, H., 1969. Excess 3He in the sea: evidence for terrestrialprimordial helium. Earth Planet. Sci. Lett., 6: 213-220.

Clarke, W.B., Jenkins, W.J. and Top, Z., 1976. Determination of tritium by mass spectrometricmeasurements of 3He. lnt. J. Appl. Radiat. Isot., 27: 515-522.

Craig, H. and Lupton, J., 1981. Helium-3 and mantle volatiles in the ocean and the oceaniccrust. In: M.N. Hill (Editor), The Sea, Vol. 7, The Oceanic Lithosphere. Wiley, New York,961 pp.

Gamberoni, L., Charriaud, E. and Kartavtseff, A., 1990. Les rapports des campagnes it la mer itbord du "Marion Dufresne": MD 53/INDIGO-3/SUZAN. In: TAAF Mission Recherche(Editor), Les Publications de la Mission Recherche des Terres Australes et AntarctiquesFrancaises, 87-04. TAAF, Paris, 141 pp,

150 P. JEAN·BAPTISTE ET AL.

Jacobs, S.S. and Georgi, D., 1977. Observations on the Southwest Indian/Antarctic Ocean. In:M. Angel (Editor), A Voyage of Discovery, George Deacon 70th Anniversary Volume. Per­gamon, New York, pp. 43-84.

Jamous, D., Mernery, L., Andric, C; Jean-Baptiste, P. and Merlivat, L., 1991. The distributionofhelium-3 in the deep Southern and Western Indian Ocean. J. Geophys. Res., in press.

Jean-Baptiste, P., Andric, C and Lelu, M., 1988. Mesure du couple tritium/helium oceaniquepar spectrometric de masse. In: lC. Guary, P. Guegueniat and RJ. Pentreath (Editors),Radioactivity: A Tool for Oceanography. Elsevier, Amsterdam, pp. 45-54.

Jenkins, WJ. and Clarke, W.B., 1976. The distribution of 3He in the Western Atlantic Ocean.Deep-Sea Res., 23: 481-494.

Kockarts, G. and Nicolet, M., 1962. Le problerne aeroncmique de l'helium et de l'hydrogeneneutres. Ann. Geophys., 18: 269-290.

Lupton, J.E. and Craig, H., 1981. A major helium-3 source at IS 0 S on the East Pacific Rise.Science, 214: 13-18.

Mantisi, F., Beauverger, C, Poisson, A. and Metzl, N., 1991. Chlorofluoromethanes in the west­ern Indian sector of the Southern Ocean and their relations with geochemical tracers. Mar.Chern., 35: 151-167.

Nowlin, W.O. and Klinck, J.M., 1986. The physics of the Antarctic Circumpolar Current. Rev.Geophys.•24 (3): 469-491.

Ostlund, G.H., Craig, H., Broecker, W.B. and Spencer, D., 1987. GEOSECS Atlantic, Pacificand Indian Ocean Expeditions, Vol. 7, Shorebased Data and Graphics. National ScienceFoundation, Washington, DC, 200 pp.

Poisson, A., Schauer, B. and Brunet, C, 1990. Les rapports des campagnes ala mer abard du"Marion Dufresne": MD53/INDIGO-3. In: TAAF Mission Recherche (Editor), Les Pub­lications de la Mission Recherche des Terres Australes et Antarctiques Francaises, 87-02.TAAF, Paris, 219.

Schlosser, P., Roether, W. and Rohardt, G., 1987. 3He balance of the upper layers of the north­eastern Weddell Sea. Deep-Sea Res., 34: 365-377.

Schlosser, P., Suess, E., Bayer, R. and Rhein, M., 1988. 3He in the Bransfield Strait waters:indication for local injection from back-arc rifting. Deep-Sea Res., 35: 1919-1935.

Stuiver, M., Quay, P. and Ostlund, G., 1983. Abyssal water carbon-14 distribution and the ageof the world oceans. Science, 219: 849-851.

Warner, MJ., 1988. Chlorofluoromethanes F-II and F-12: their solubilities in water and sea­water and studies of their distribution in the South Atlantic and North Pacific Oceans. Ph.D.Thesis, University of California, San Diego, 194 pp.