no DISCOVERY REPORTS 



station (Deutschland St. 125) is most probably separated from the bottom water farther 

 north by a shallow submarine ridge (see Brennecke, 1921, p. 33). There may, however, 

 be a break in the ridge, and there is also a great expanse of shelf farther west from which 

 the water may sink. 



THE MOVEMENTS OF ANTARCTIC BOTTOM WATER 



In order to illustrate the principal movements of the Antarctic bottom water Plate 

 XLIV has been prepared showing the potential temperature of the bottom water at 

 depths greater than 4000 m. In the southern part of the Atlantic Ocean it is based on the 

 charts given by Wiist (1933, pis. i, ii), which are themselves based on all the data that 

 was available including the observations made by the 'Discovery II' and 'William 

 Scoresby '. Other observations made since Wiist 's charts were published have also 

 been used. In the Indian and Pacific Oceans the chart is based principally on the 

 observations made during the circumpolar cruise and on a cruise across the southern 

 part of the Antarctic Zone in the Pacific Ocean (Mackintosh, 1935). The 4000-m. 

 bottom contour is based largely on a bathymetric chart published by the American 

 Geographical Society (193 1), but the chart has been modified in several localities after 

 a very rough examination of our own soundings ; it is therefore only approximately 

 correct. 



According to Wiist the coldest bottom water in the open sea lies south of 72 S between 

 40 and 45 W, where its potential temperature at a depth of 2653 m. (calculated from 

 Brennecke 's measurements) is as low as — 1-02° C. The temperature distribution shows 

 that from this region the cold water spreads first to the north and then to the east. It is 

 very probable that the formation of bottom water, by the sinking of cold surface water, 

 may take place all along the east coast of Graham Land in winter, but the section published 

 by Nordenskjold (1917, pi. 2) and our observations between the South Shetland Islands 

 and the South Orkney Islands show that in the northern part of the region at least, the 

 bottom water is not formed in summer. 



Several reasons can be suggested to explain the very large formation of bottom water 

 in the Weddell Sea. The surface water in the southern part of the sea belongs to the 

 current which flows towards the west along the coast of the Antarctic Continent. Even 

 in the Indian Ocean and the eastern part of the Atlantic Ocean this current must have 

 a high salinity in winter, and owing to the continued separation of sea-ice from it as it 

 flows towards the Weddell Sea its salinity must keep increasing. Brennecke (1921) 

 recorded surface salinities as high as 34-49 °/ 00 . The deep water in the south and 

 western parts of the Weddell Sea also has a lower temperature and salinity than it has 

 in the open sea in any other part of the Southern Ocean ; like the surface water it travels 

 along the continental slope from the western part of the Indian Ocean, and owing to the 

 continued mixing with the surface and bottom waters, it forms a weaker barrier be- 

 tween the surface and bottom layers in the Weddell Sea than it does anywhere else 

 along the edge of the continent. 



The effect of the earth's rotation on the current towards the west in the southern part 



