8 DISCOVERY REPORTS 



CURRENTS WITHIN THE ANTARCTIC ZONE OF 

 THE SOUTH-WEST ATLANTIC 



The Antarctic surface water flowing out from the BeUingshausen Sea follows a simple 

 course (Fig. 2). It can be shown that there is a moderately strong set from the neigh- 

 bourhood of Adelaide Island outside the Biscoe and Palmer Archipelagoes to the South 

 Shetland Islands. The surface water in both the major portion of the Bransfield Strait 

 and in the southern part of Drake Passage thus originates in the Bellingshausen Sea. 

 It continues north-eastwards towards South Georgia, off the northern and western 

 coasts of which island it can still be recognized, but farther east its identity becomes 

 merged with that of the "old" Antarctic surface water from the Weddell Sea. In 

 passing through the southern half of Drake Passage, this Bellingshausen Sea surface 

 water constitutes the cold part of the "west-wind drift". 



From the nature of the phytoplankton it would appear that water of this type was 

 encountered round Elephant Island during the seasons studied, but at the South 

 Orkneys, farther to the east, the surface water appears to be of Weddell Sea origin. This 

 group must lie very near the junction of the two currents, where considerable mixing 

 probably takes place. The Bransfield Strait appears to be occupied mainly by com- 

 paratively old Bellingshausen Sea water, except in the north-eastern corner, where, 

 as can be clearly shown from both hydrological and plankton investigations, there is a 

 comparatively small eddy of Weddell Sea surface water round Joinville Island. This 

 does not extend farther north than the middle of the strait, and not beyond Astrolabe 

 Island in a south-westerly direction. From the above it will be seen that the Antarctic 

 surface water originating in the BeUingshausen Sea follows in the main the north- 

 easterly trend common to all Antarctic surface waters, except in very high latitudes. 



Conditions in the Weddell Sea are somewhat more complicated. To begin with it is 

 a very deep bight penetrating farther to the southward than any other known indenta- 

 tion, with the exception of the comparatively shallow Ross Sea. Further, while its 

 eastern boundary — Coats Land — does not extend north of the Antarctic Circle, the 

 western limits of the Weddell Sea are continued north from Snow Hill Island through 

 Graham Land to the north of Joinville Island in 63° S. Now, in high southern latitudes 

 the prevailing winds are from the east, while the great west winds prevail at least as far 

 as 60° S. Consequently a well-defined clockwise circulation is set up within the Weddell 

 Sea surface water, entering round the coasts of Coats Land and farther north, and 

 flowing round and out towards the South Sandwich Islands. This is roughly indicated 

 in Fig. 2, where it will be seen that it is possible to subdivide the Weddell Sea surface 

 water into two types. The water which flows in along the coasts of Coats Land penetrates 

 far into the bight, and when it turns north is apparently confined to a comparatively 

 narrow belt close against the Graham Land coast, finally issuing from the north-western 

 corner of the sea. The eddy round Joinville Island into the Bransfield Strait is composed 

 of surface water of this type. From Joinville Island the main body of the stream, during 

 the seasons with which we are dealing, continued in a north-easterly direction, passing 



