XBT Station No. 



26 27 28 29 30 



I I I i I 



34 36 3840 



33 35 37 39 



I r I I I I LJ 



43 



4142 44 



I I I I 



45 



I 



46 



47 



I 



48 



I 



49 



_i 



50 



L_ 



51 



I 



6 7 6 7 5.8 5.8 5.1 



SURFACE TEMP 



53 50 43434142 4.0 3.7 3.7 37 3.7 35 3.i 



" h \^/; 



18.5 



37.1 Km. 

 —I 

 20 NM. 



Figure 17. — Expendable bathythermograph (XBT) section across the polar front. Contours are in °C. Starting and ending 

 positions for section are 56 44.8'S, 65 33.4' W and 5902.08, 63 02.5' W. 



urements will be an efficient means of monitoring geostrophic 

 fluctuations of the mean down-channel flow at 500 m depth. 

 The existing hydrographic data from Drake Passage show 

 the relative baroclinic transports to be nearly constant. To the 

 extent that this is true, the fluctuations in total transport 

 through the Drake Passage will be measured by the pressure 

 gauges. 



ISOS includes individual theoretical studies and regular 

 meetings of a panel on theoretical studies. The studies empha- 

 size circumpolar current dynamics. Included are laboratory 

 investigations, an analytical study of topographically-induced 

 jets in a zonal channel, and analytical studies of the inter- 

 action of bottom topography and circumpolar current. An- 

 other ISOS project provides for the publication of a Southern 

 Ocean Atlas. Completion of the atlas is expected in 1978. 



An ISOS project initiated in 1976 obtains XBT sections 

 from supply and research vessels that cross the circumpolar 

 current (fig. 21). These data, in conjunction with satellite ob- 



servations, will allow investigation of the temporal and spatial 

 changes of the Polar Front. 



From January to February 1977, a collaborative effort 

 with the U.S.S.R. to obtain hydrographic and current data 

 along 130°E from the Soviet R/V Professor Zubov was 

 carried out. Unusually bad weather prevented accomplishment 

 of planned objectives; for example, of the 24 hydrographic 

 stations planned, only 8 were obtained. A number of XBT 

 surveys were performed that documented the existence of a 

 cold-core eddy at 132°E, 51°S. 



In 1978, a cluster of current meters will be deployed in 

 the Circumpolar Current to the east of Campbell Plateau at 

 about 54°S, 174°E. Upstream pressure fluctuations across 

 Macquarie Ridge will be monitored with pressure gauges. The 

 moored instruments will be retrieved in austral winter/spring; 

 and at that time, the formation of subantarctic mode water will 

 be studied. These studies will be carried out in cooperation 

 with New Zealand and Australian oceanographers. 



34 



