ic,8 DISCOVERY REPORTS 



received more additions of fresh water. In the eastern half of the Scotia Sea the saHnity 

 of the water is greater because it has its origin in the Weddell Sea. There is still a 

 minimum salinity in the east of the sector just south of the convergence ; but it is not 

 so well defined because the salinity of the Bellingshausen Sea water increases after it 

 reaches its minimum in the west of the Sea. Near South Georgia Bellingshausen Sea 

 water is warmer than Weddell Sea water, because it has travelled farther from its source 

 where it is as cold as, or even colder than, Weddell Sea water. 



The greater salinity of the Weddell Sea water is probably due to the fact that whilst 

 it has been flowing round the Weddell Sea in the cyclonic movement described above, 

 it has received continual additions of water of greater salinity from the deep water, 

 which upwells in the centre of the movement. In addition, more ice will probably be 

 formed over Weddell Sea water in winter because the sea extends to such high latitudes, 

 and this too will increase the salinity of the water in winter. 



To decide the origin of a body of water which is found near South Georgia it is best 

 to rely on charts showing the distribution of temperature and salinity based on data 

 collected at the time. These diagrams will show the greater influence of Bellingshausen 

 Sea water in the west and of Weddell Sea water in the east. The shape of the isotherms 

 and isohalines will show the direction of continuous movements. The lines will approach 

 close together where the boundary between the two waters is well defined and will be 

 farther apart when the waters are well mixed. The water of greater salinity, provided it 

 is continuous with similar water farther east, can be assumed to be Weddell Sea water 

 and the water of lesser saHnity to be Bellingshausen Sea water. Also, colder water will 

 be Weddell Sea water and warmer water Bellingshausen Sea water. Further evidence 

 can be obtained from a chart showing the topography of the sea surface based on cal- 

 culations of the depth of some deep isobaric surface, which can be considered to be 

 horizontal, below it. Such a chart also shows the directions of continuous movements, 

 for these follow approximately the contours on the chart and have velocities which are 

 inversely proportional to the distance of the contours apart. 



Fig. 8, which has been used to show the direction of the surface currents in the 

 Falkland Sector, also shows the distribution of temperature over a wider area than that 

 covered by Fig. 12. The shapes of the isotherms are not quite so accurate, since the 

 observations on which the diagram is based were spread over a slightly longer time, 

 November lo-January 10; the surface also is more rapidly affected by changes due 

 to the approach of summer than is a surface layer 100 m. deep. The isotherms are not, 

 however, seriously distorted, and they give additional information about the Weddell 

 Sea current. They show the drift south and west into the Weddell Sea, as well as the 

 direction of the Weddell Sea current flowing out of the sea. The lowest surface tem- 

 perature found in Antarctic surface water was -i-68° C. in the middle of the Weddell 

 Sea, and the highest 3-5° C. at the convergence north of South Georgia. 



Fig. 14 uses data, already employed in Fig. 5, to show the changes which take place 

 in the temperature of the surface layer during the year. It shows the changes at the 

 surface and at depths of 50, 100, and 150 m., and is based on Sts. WS 160, 268, and 



