Marine Chemistry, 3S (1991) 123-136Elsevier Science Publishers B.Y., Amsterdam

Tritium profiles in the Weddell Sea

123

Reinhold Bayer"and Peter Schlosser""l nstltut flir Umweltphysik der Universitiit Heidelberg, D·6900 Heidelberg, FRG

bLamont-Doherty GeologicalObservatoryandDepartment of GeologicalSciences of ColumbiaUniversity, Palisades, NY 10964, USA

(Received 31 December 1990; accepted i 3 March 199i )

ABSTRACT

Bayer. R. and Schlosser, P., 1991. Tritium profiles in the Weddell Sea. Mar. Chem., 35: 123-136.

Tritium data were collected between 1985 and i 987 on several cruises of the German researchicebreaker "Polarstern" to the Weddell Sea. Maximum trit ium concentrations in the surface watersare of the order of200 mTU . The minimum values observed in the Weddell Sea Deep Water at about1000 m depth are about 15-40 mTU . The bottom waters show trit ium concentrations of about 70­100 mTU in the cent ral gyre, increasing to about 120 mTU in the north western corner of the WeddellSea. The overflow ing Ice Shel f Water observed on the continental slope west of the Filchner Depres­sion has tritium concentrations close to those of the surface waters , indicating rapid renewal of thiswater mass. The data reflect the rapid renewal of the bottom waters in the northwestern comer of theWeddell Sea and the mixing of bottom water from this boundary curr ent into the bottom waters ofthe central Weddell Gyre.

INTRODUCTION

Transient tracers, i.e, radioactive or stable isotopes or chemical com­pounds of anthropogenic origin, have entered the ocean surface waters forseveral decades at relatively well-known rates. Some of these trace substancesare now widely used tools for studying deep water formation and circulationon time scales of months to decades. One of the most often used tracers insuch applications is tritium, the radioactive isotope of hydrogen (e.g. Broeckerand Peng, 1982). Tritium was delivered to the atmosphere mainly during thesurface nuclear weapon tests in the early 1960s, and enters the ocean surfacewaters by water vapor exchange, precipitation and river runoff (e.g. Weissand Roether, 1980) . The anthropogenic 'bomb' tritium signal masked thenatural tritium level by several orders of magnitude. Penetration of bombtritium from the surface waters into the deeper layers ofthe ocean can be usedto study pathways and time scales of deep and bottom water formation (e.g.Miinnich and Roether, 1967; Broecker et al., 1986; Ostlund and Grall , 1987) .For such studies determination of tritium concentrations in the source re­gions of the deep waters is of special interest. The source concentration rep-

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

124 R. BAYERAND P. SCHLOSSER

resents the initial tracer signal with which the observed patterns at locationsremote from the sources have to be compared.

An important source of deep and bottom waters in the southern hemi­sphere is the Weddell Sea. Although there is no doubt about the importanceof the Weddell Sea for deep water formation, only few tritium measurementsexist from this region. Besides the fact that access to the Weddell Sea is diffi­cult because of the heavy ice that perennially covers its central and westernareas, tritium distribution in the southern hemisphere is more difficult tomeasure than in the northern hemisphere. As most of the 'bomb' tritium wasset free in the northern hemisphere, a large asymmetry in oceanic tritium con­centration is observed between the southern and northern hemispheres. Thetritium concentrations in the southern hemisphere are about an order ofmag­nitude lower than those in the northern hemisphere (e.g. Broecker and Peng,1982). After the peak in surface nuclear weapon tests in the late 1960s, thesouthern hemisphere tritium concentrations decreased to surface values be­low 500 mTU in 1985 (e.g. Michel, 1978; Weiss et al., 1979; Jenkins et aL,1983), making it difficult to resolve the fine structure of the tritium distri­bution with conventional measurement techniques. Only the development ofhelium isotope mass spectrometry (mainly during the last decade) has al-

Weddell Sea

TRITIUM PROFILES IN THE WEDDELL SEA 125

Fig. I. Geographical position of the ANT III/3 (January-March 1985), ANT Y/2 (July-Sop­tember 1986) and ANT V/4 (January-March 1987) tritium stations used in this contribution.(a) Weddell Sea; (b) Filchner Depression and continental slope. (For a detailed description ofthe cruises see Hempel (1985) (ANT III), Schnack-Schiel (1987) (ANT V/2) and Miller andOerter (1989) (ANT V/4) .)

lowed measurement of tritium at low levels with high sensitivity by the 3Heingrowth method (e.g. Clarke et aI., 1976; Jenkins et al., 1983; Bayer et aI.,1989). Using this method, measurements with a precision that is sufficientto resolve the southern hemisphere tritium distribution can be obtained.

This contribution presents a representative tritium data set from the Wed­dell Sea and discusses its potential for studies of the processes and time scaleof deep water formation. The results presented here are the first high resolu-

126 R. BAYER AND P. SCHLOSSER

tion measurements of an extensive sample set including all water masses ofthe Weddell Sea except the western shelf waters.

SAMPLE COLLECTION AND MEASUREMENT

Samples for measurement of tritium were collected on several cruises of theGerman research icebreaker "Polarstern" to the Weddell Sea between 1985and 1987 (ANT III/3, January-March, 1985; ANT V/2, July-September,1986; ANT V/4, January-March, 1987; for geographical positions of the tri­tium stations, see Fig. 1). The samples were taken from standard Niskin sam­plers (5 or 10 1 volume) mounted on a conductivity-temperature-depth(CTD)/rosette system equipped with a Neil Brown CTD instrument. Usu­ally, between 12 and 36 samples were collected per station.

The water samples were degassed in the Heidelberg helium isotope labora­tory using a vacuum extraction unit and stored for some months in glass bulbsfor 3He ingrowth. After this time, the tritiogenic 3Heproduced by the tritiumdecay was extracted and measured in a dedicated helium isotope mass spec­trometer (MM 3000, VG Isotopes, Winsford, Cheshire (Lynch and Kay,1981 ) ). The precision of the tritium measurement was about ± 1-2% and thedetection limit was of the order of 5-10 mTU (1 mTU means a tritium tohydrogen ratio of 10- 21 ). Details of the measurement procedure have beendescribed by Bayer et al. (1989).

RESULTS

The stations occupied in the central Weddell Sea during southern summer1985 show surface tritium concentrations close to 200 mTU (Fig. 2). Thereis a slight decrease in tritium in the underlying Winter Water (WW) at somestations. Winter Water is the remnant of the winter mixed layer which isformed by convection under the winter sea ice cover (e.g. Gordon and Huber,1984, 1990). It is marked by a pronounced temperature minimum at depthsof about 100 m (Fig. 3). Below the WW the tritium concentrations decreaserapidly to minimum values of about 15-30 mTU in the Circumpolar DeepWater (CDW) and the Weddell Sea Deep Water (WSDW). CDW is markedby potential temperatures above 0°C and is observed at some hundreds ofmeters depth (Fig. 3). It is derived from the Antarctic Circumpolar Current(ACC) by upwelling from about 3000 m depth (e.g. Whitworth and Nowlin,1987). WSDW (often called Antarctic Bottom Water, AABW) is the waterfound between the CDW and the Weddell Sea Bottom Water (WSBW). Asthe potential temperatures of the Antarctic Circumpolar Current are aboveDoC, WSDW has to be formed within the Weddell Sea. Below the tritiumminimum located at about 1000 m depth, the tritium concentrations increasemore or less monotonically to values of about 70-100 mTU in the WSBW.

TRITIUM PROFILESIN THE WEDDELL SEA 127

o

200

il OO

WEDDELL SEA (S, SUMMER 1985)r-r-r-t-r-r-r-

-....... ~........~~'WW-.......,->-6-< ...-

-:. COW

600

8 00

1000 ......

- WSDW2000

300 0

E40 00

.c+J0

5000 t IQ)

'00

~ ~~_ ..-e€t-H........_ ~

_-_, """""'" WSBW, I , , I , 1 ,

50 100

Q N 3 o 2 JJ

o Qbo••

2 00

400

600

800

1000

2000

3000

"'0'"" 0 ..

0 "00 COW<0

0

0

0

0 "Q .. WSDW

/Y "

e..

~o

0 "4000

.c

.w0­Q)'0

0 "O O'o[1,.%WSBW

I I I \ I- j ,5 - j - 0 5 0 0,5 j

pot , t emper ature [OC lo 2~3 0 2 <1 4 • 2 45

Fig. 3. Profiles of potential temperature for the tritium stations shown in Fig. 2. The character­istic water masses of the central Weddell Sea are indicated.

(S.WINTER 1986)

I....,....~ IWW~HH

128

WEDDELL SEA0 I

COW --200 ....eH-->-eo-<

~OO --600 ~

800 ......1000 ~--.

.-... WSDW""""2000 --.......\-&-11--&'1"'"

~

3000 '"€>+-<HH-

.....-E!-B-'~~ooo

.c _\'t!i--.....~D.

ill 5000 '"'i>e-<D0 50

e 234

WSBW

100 150tritium

0266 .317

200[mTU]

R. BAYER AND P. SCHLOSSER

3000

~ aooo

Fig. 4. Tritium profiles from ANT V/2 stations occupied on a section across the Weddell Seaalong the Greenwich meridian during southern winter 1986. For geographical positions of thestations, see Fig. 1. Error bars are as in Fig. 2.

WEDDELL SEA (S.WINTER 1986)o Sf / .. 1 1 I I I

" .Ql200 WW COW + :l>

" ~

~oo 0 ... 00

<9

600 0 0'"

& 00

800 •

1000 <9 o·0&+

SO. WSDW"0 +

2000 <7Q#

8~";:

<t:J+~+

~c~~ WSBW

I I ,Ii I I I I'

-1.5 -1 -'0 5 0 0.5 1pot. temperature rOC]

o 2304 0 266 • 317

Fig. 5. Profiles of potential temperature for the ANT V/2 tritium stations shown in Fig. 4. Thedata are taken from Huber et al. (1989).

(a) tr I t I um [mTU] (b) t r It Ium [mTU] (c) tr I t I um fro Tu1 "";<la 50 100 150 20 0 25 0 0 50 100 150 200 250 0 5 0 10 0 15 0 200 2 5.) ::j

o ~.j I I j j I j ~i i I j i j~ 1 i i j j I i~ O ~ " " ii

j j I iI I " " I I i j ~ a ~ j " , I i I I I I ' i j , I i i i '1 c»: ....... If 3::

-1"tl

~ '">---+--i 0

j ."

20 0 r \ t=200 200 ,..-;-; rn

'"\ z~ I-rl

-I:t

-+< m>+< ::E

400 40 0 Hi 400 ....... rni-H 0

E E 0.s m~ ~ r-

f+< H-l r-.c s: .c \ '"..... H-l ..... ..... ~:i; 6 00 H-i

~ 60 0 l-H ~ 6 0 0 l-H

D D D , II I

- 2 . 2 - 2 -1.8 - 1. 6 - 1 . 4 -1. 2 - 1 -2 . 2 - 1 -2 2 - 2 - 1 .8 - 1. 6 - 1 . 4 - 1.2 - ]

pot . t empe r a t ur e [' C] [' C] pot. t e mpe ra t ur e I ' C]

St at . 727 x t.eecer-e t or-e St a t .729 x t.emoer-e t er e St a t . 73 " x t enoer-e t cr-c+ tr l tlum + tr" UlUm + tr- l t l um

Fig. 6. Profiles of tritium and potential temperature for ANT V/4 stations located on the sill separating the Filchner Depression from theWeddell Sea. (a) Station 727; (b) Station 729; (c) Station 731. For geographical positions, see Fig. 1. Error bars as in Fig. 2. The vertical lineindicates the freezing point of seawater at surface pressure (salinity 34.0; Toole, 198I ).

N'0

130 R. BAYER AND P. SCHLOSSER

oCONT. SLOPE (S.SUMMER 1987)

TT"TT

500

1000

"'--"'::--===:---r'i'< IS W-.

" , I " , , I150 200 250

t r r t i urn [mTUlo 753 0 757 0 773 v 77A

1500

.C-w 2000'0-WD ""1,,,,1,

o 50 100

Fig. 7. Tritium profiles for ANT V/4 stations located on the continental slope west of the Fil­elmer Depression. For geographical positions, see Fig. 1. Error bars as in Fig. 2.

WEDDELL SEA IS .SUMMER 1987)

0 <> •• <>

1000

2000

WSDW3000 o ..

E.

4000 0" dO>

'".c <> C) '" .,oi WSBW.W dc)'"0-W 5000 I I ID

0 50 100 150 200tritium [mTU]

0820 o 822 <> 824v 826 .c. B28 • 784

Fig. 8. Tritium profiles from ANT V/4 stations located in the northwestern corner of the Wed­dell Sea. For geographical positions, see Fig. 1. Measurements precision is about 5 mTU.

WSBW is defined as the water with potential temperatures below -0.7 QC

(Carmack and Foster, 1975a). There is an indication of a slight secondarytritium minimum at Station 244 at about 3000-3500 m depth. The bottomwater concentrations are higher in the central Weddell Sea (Station 244) thanin the southern boundary regime (Station 245 ).

TRITIUM PROFILES IN THE WEDDELL SEA 131

The tritium profiles from the southern winter 1986 cruise (Fig. 4) are verysimilar to the summer profiles (Fig. 2). The winter mixed layer tritium val­ues are close to the 1985 summer surface values at the northern and centralWeddell Sea Stations 234 and 266 and significantly lower at Station 317, lo­cated at the southern boundary. The tritium concentrations in the minimumlayer (about 1000 m) are higher than in the 1985 profiles (30-40 mTU com­pared with 15-30 mTU). The bottom water concentrations are about 75 mTU,with no significant north/south trend observable at the stations presentedhere. All stations from the 1986 winter cruise are located in the warm regime(potential temperature of the temperature maximum above 0.5°C; Fig. 5) ofthe Weddell Gyre (Gordon and Huber, 1984), whereas Stations 243 and 244from the 1985 summer cruise are located in the cold regime (potential tem­peratures in the temperature maximum below 0.5°C, Fig. 3).

So far we have measured only shelf samples from the southern shelvesaround the Filchner Depression. Stations 727, 729 and 731, located on a sec­tion on the sill separating the Filchner Depression from the Weddell Sea, showsurface tritium concentrations close to 200 mTU (Fig. 6 a-c). Belowthe sur­face waters the tritium concentrations generally decrease slightly at interme­diate depths (about 200-400 m) and increase again towards the bottom. Thereis no clear correlation with the temperature profiles. The highest tritium val­ues (about 250 mTU) are observed in Ice Shelf Water (ISW), which is markedby potential temperatures below the surface freezing point ( -1.84 a C for waterwith a salinity of 34.0; Fofonoff and Millard, 1983). ISW is formed by inter­action of Western Shelf Water (WSW) with glacial ice under the Filchner/Ronne Ice Shelf (e.g. Carmack and Foster, 1975b; Foldvik et al., 1985).

The tritium profiles from stations located on the continental slope west ofthe Filchner Depression again have tritium concentrations of about 200 mTUin the surface waters (Fig. 7). The tritium content of the underlying waterdecreases to a minimum of about 35 mTU at depths of about 1000-1500 m.Below this minimum there is a sharp increase in a very thin bottom layer,which is well pronounced at all stations. The tritium concentration in thisoverflowing ISW is as high as the surface water concentration at Stations 753and 757 and only slightly less at Stations 773 and 774.

The tritium profiles from stations in the northwestern corner of the Wed­dell Sea occupied in southern summer 1987 (Fig. 8) are marked by relativelyhigh tritium concentrations in the bottom water, reaching values of about 120mTU at Stations 822 and 828. The overlying waters have similar tritium con­centrations to the profiles in the central Weddell Sea, with the exception ofsomewhat lower surface concentrations (165 mTU compared with about 200mTU).

132

DISCUSSION

Surface waters

R. BAYERAND P. SCHLOSSER

For the application of tritium as a 'dye' in studies of deep water formationand circulation it is important to know its distribution in the source watermasses for the deep water. From our present measurements it appears as ifthe tritium distribution in the surface waters is fairly homogeneous, with av­erage values close to 200 mTU. The mean concentrations fall on the extrap­olation of the curve fitted through Southern Ocean surface data published byJenkins et al. (1983) (Fig. 9). However, our first tritium data from theFilchner Depression seem to indicate that the tritium distribution in the up­per shelfwaters may show a high variation. Such variations are expected fromthe fact that tritium input to the surface waters is to some degree controlledby the ice cover, which can be very patchy in the shelf regions. Further varia­tion can be expected in the winter mixed layer as a result of varying amountsof CDW incorporated into the winter mixed layer. This effect probably ac­counts for the relatively low tritium surface concentrations observed at Sta­tion 317 compared with Stations 234 and 266 (Fig. 4). For a first-order ap­proximation of a tritium input function for model studies of the deep waterformation, the curve derived by Jenkins et al. (1983), extrapolated to 1987(Fig. 9), can be used.

Deep andbottomwaters

It is evident that the highest tritium concentrations in WSBW are observedin the northwestern corner. This is consistent with the well-known fact that

Fig. 9. Tritium concentration as a function of time for Weddell Sea surface waters (adaptedfrom Jenkins et al. (1983) and supplemented by data from this study). Our 1985-1987 datapoints are calculated as the mean of all surface water tritium measurements. The bars indicatethe range between the highest and lowest values.

TRITIUM PROFILES IN THE WEDDELL SEA 133

new bottom water is formed on the shelves of the western Weddell Sea and,after flowing down the continental slope, is transported out of the WeddellSea at the western boundary of the Weddell Gyre. The relatively high tritiumconcentrations in the bottom waters in the northwestern corner comparedwith the central Weddell Sea is further evidence for the renewal ofWSBW bya relatively narrow boundary current from which the water spreads into thecentral Weddell Sea. This feature is also clearly visible in the CFC distribu­tion (e.g. Bullister, 1989a,b).

The tritium concentrations of the bottom waters can be used to check thebottom water formation rates derived from hydrographic (Carmack and Fos­ter, 1975a) and early tritium measurements (Weiss et al., 1979; Jenkins etal., 1983). For this purpose we have to construct a tritium vs. time curve forthe water feeding the WSBW. As we measured only the tritium concentrationin ISW and the overflowing water on the continental slope northwest of theFilchner Depression, we assume that the WSBW (defined as water with po­tential temperatures below - 0.7 0 C) is composed of a mixture of this over­flowing water and CDW. The tritium concentration as a function of time can

1200 I--

• I

1000 I--

• 3 .

80 0

1990year

I

19801970

+ surface Input - functIon

o F 1 1chner ove r f l ow ( I SW at - 2 _05 ' C)

W boundar y current (ne w WSBI, at - 1 _O' CI

o WSB\~-bu x (t emp , -0 , 8'C, I Sw- ov e r f la w 0 ,2 Svl

400 l-

200 f-

600

E:Jrl

.w

.r-t

c,.w

,-,

:Jl­E

Fig. 10. Tritium vs. time curves for Weddell Sea surface waters (curve 1), overflowing ISW(curve 2), newly formed WSBW found in the northwestern Weddell Sea (curve 3) and WSBWfound in the central Weddell Sea (curve 4) . For explanation , see text.

134 R. BAYER AND P. SCHLOSSER

be reconstructed for the overflow if we simulate the formation of ISW by ex­change of surface water represented by the curve shown in Fig. 9 with a well­mixed reservoir with a renewal time of about 4 years. The resulting tritiumvs. time curve (Fig. 10, curve 2) is used as the source water for WSBW. Theformation ofWSBW with a potential temperature of -1.0°C (the lowest po­tential temperature observed at our stations in the northwestern Weddell Sea)is now simulated by mixture of the source waters with CDW (with a mixingratio of 53% CDW and 47% ISW). Additionally, a transit time from theshelves to the deep Weddell Sea (northwestern corner) of2 years is assumed.The resulting tritium vs. time curve for the newly formed WSBW in theboundary current observed in the northwestern Weddell Sea fits the observa­tions well (Fig. 10, curve 3). Ifwe assume that the ISW flux down the conti­nental slope is about 1 Sv (Foldvick et al., 1985), the resulting productionrate of WSBW by overflowing ISW is about 2.1 Sv. This value is in goodagreement with WSBW formation rates estimated by Carmack and Foster(1975a), Weiss et al. (1979) and Jenkins et al. (1983).

An alternative approach to derive the WSBW formation rate is to use asimple time-dependent single-box model. The well-mixed box represents theWSBW,which is fed by a mixture of shelfwaters (in our case ISW) and CDW.The average tritium concentration in the bottom waters of the central Wed­dell Sea (mean potential temperature -0.8°C) is about 70 mTU, i.e. signif­icantly lower than that observed in the newly formed WSBW in the north­western corner of the Weddell Sea. To fit the observations with this model, ashelf water flux of about 0.2 Sv is required (Fig. 10, curve 4). This flux issignificantly lower than the ISW flux observed by Foldvik et al. (1985), whichhas to be regarded as a minimum value because there are probably additionalWSBW sources on the western shelves of the Weddell Sea. This result can beexplained by the fact that part of the newly formed WSBW escapes to thenorth before mixing into the central Weddell Sea.

The waters below the WW and above the WSBW generally have low tritiumconcentrations, reaching a minimum of about 15 mTU (Fig. 2). This is causedby the slow renewal of these waters by surface water. Within the CDW andWSDW there seems to be some fine structure; in particular, a secondary tri­tium minimum at depths ofabout 3000-4000 m observed at Stations 244 and245 (Fig. 2). The difference between the tritium concentrations in the tri­tium minimum is most probably related to the oceanographic circulation butsome experimental bias cannot be excluded.

CONCLUSIONS

The first high-resolution tritium profiles from the Weddell Sea demonstratethat tritium can be measured with sufficient sensitivity and that the tritiumdistribution shows clear signals yielding information on the pathways of the

TRITIUM PROFILESIN THE WEDDELLSEA 135

newly formed deep waters. For a detailed study of the processes'and rates ofdeep water formation, more measurements are needed, especially from thesource region on the western shelf areas.

ACKNOWLEDGMENTS

The officers and crew of R/V "Polarstern" provided excellent assistanceduring several cruises to the Weddell Sea. The Alfred Wegener Institute forPolar and Marine Research, Bremerhaven, provided logistical support for ourwork. Wolfgang Roether and Karl Otto Miinnich gave advice in many discus­sions. Svein 0sterhus and Gerd Rohardt provided the hydrographic data fromANT V/4 and ANT III/l This work was supported by the Deutsche For­schungsgemeinschaft. This is L-DGO Contribution No. 4814.

REFERENCES

Bayer, R., Schlosser, P., Bonisch, G., Rupp, H., Zaucker, F. and Zirnrnek, G., 1989. Perform­ance and blank components of a mass spectrometric system for routine measurement ofhelium isotopes and tritium by the 3He ingrowth method. Sitzungsber. Heidelb. Akad. Wiss.,Springer-Verlag, Math.-Naturwiss. Kl., 5, Abhandlung: 241-279.

Broecker, W.S. and Peng, T.H., 1982. Tracers in the Sea. Eldigio Press, New York, 690 pp.Broecker, W.S., Peng, T.H. and Ostlund, H.G., 1986. The distribution of bomb tritium in the

ocean. J. Geophys. Res., 91: 14331-14344.Bullister, J., 1989a. Chlorofluorocarbons as time-dependent tracers in the ocean. Ocean. Mag.,

2 (2 ): 12-1 7.Bullister, J., 1989b. Dissolved chlorofluorocarbon studies in the Weddell Sea. Antarct. J. U.S.,

24(5): 142-143.Carmack, E.C. and Foster, T.D., 1975a. On the flow of water out of the Weddell Sea. Deep-Sea

Res., 22: 711-724.Carmack, E.c. and Foster, T.D., 1975b. Circulation and distribution of oceanographic proper­

ties near the Filchner Ice Shelf. Deep-Sea Res., 22: 77-90.Clarke, W.B., Jenkins, W.J. and Top, Z., 1976. Determination of tritium by mass spectrometric

measurement of 3He. lnt. J. Appl. Radial. Isot., 27: 515-522.Fofonoff, N.P. and Millard, R.C., 1983. Algorithms for computation offundamental properties

of seawater. UNESCO Tech. Pap. Mar. Sci.,44: 53 pp.Foldvik, A., Gammelsred, T. and Terresen, T., 1985. Circulation and water masses on the

southern Weddell Sea shelf. In: Jacobs, S.S. (Editor), Oceanology of the Antarctic Continen­tal Shelf, Antarctic Research Series, Vol. 43. Am. Geophys, Union, Washington, DC, pp, 5­20.

Gordon, A.L. and Huber, B.A., 1984. Thermohaline stratification below the Southern Oceansea ice. J. Geophys. Res., 89: 641-648.

Gordon, A.L. and Huber, B.A., 1990. Southern Ocean winter mixed layer. J. Geophys. Res., 95:II 655-11 672.

Hempel, G. (Editor), 1985. Die Expedition ANTARKTIS III mit FS "Poiarstern"1984/85.Reports on Polar Research, 25, Alfred Wegener Institute, Bremerhaven.

Huber, B.A., Mele, P.A., Haines, W'E" Gordon, A.L., Jennings, J.C., Gordon, L.L, Weiss, R.F.Van Woy, F.A. and Salameh, P.K., 1989. CTD and hydrographic data from cruise ANT

136 R. BAYER AND P. SCHLOSSER

V/2 or R/V "Polarstern", Data Rep. LDGO-89-3 , Lamont-Doherty Geological Observa­tory of Columbia University, Palisades, NY.

Jenkins, W.J., Lou, D.E., Pratt, M.W. and Boudreau, R.D. , 1983. Anthropogenic tritium inSouth Atlantic bottom water. Nature, 305: 45-46.

Lynch, M.F.C. and Kay, D.J., 1981. Performance of a mass spectrometer for determining lowtritium levels from 3Hej4He measurements. In: Methods of Low-Level Counting and Spec­trometry. IAEA-SM-252/47, IAEA, Vienna, pp. 511-523.

Michel , R.L., 1978. Tritium distributions in Weddell Sea water masses . J. Geophys. Res., 83:6192-6198~

Miller, H. and Oerter, H. (Editors), 1989. Die Expedition ANTARKTIS V mit FS " Polarstern"1986/87, Bericht von den Fahrtabschnitten ANT V/4-5 . Rep. Polar Res., 57, Alfred Wege­ner Institute, Bremerhaven.

Milnnich, K.O. and Roether, W., 1967. Transfer of bomb 14C and tritium from the atmosphere

to the oceans: internal mixing of the ocean on the basis of tritium and 14C profiles. In: Ra­dioactive Dating and Methods of Low-Level Counting. IAEA, Vienna, pp. 93-103.

Ostlund, H.G. and Grall, C; 1987. Transient tracers in the ocean, North and Tropical Atlantictritium and radio carbon . Tritium Lab. Data Rep. 16, University of Miami, Rosenstiel Schoolof Marine and Atmospheric Science, Miami, FL.

Schnack-Schiel, S. (Ed itor), 1987. Die Winter-Expedition mit FS "Polarstern" in die Antarktis(ANT V/1-3). Reports on Polar Research, 39, Alfred Wegener Institute, Bremerhaven.

Weiss, R.F., Ostlund, H.G. and Craig, H., 1979. Geochemical studies of the Weddell Sea. Deep­Sea Res., 26: 1093- I 120.

Weiss, W. and Roether, W., 1980. The rates of tritium input to the world oceans. Earth PlanetSci. Lett ., 49: 435-446.

Whitworth, T., III , and Nowlin, W.D., Jr. , 1987. Water masses and currents of the SouthernOcean at the Greenwich meridian. J. Geophys. Res., 92: 6462-6476.