io DISCOVERY REPORTS 



which no temperature inversion is present owing to the poor development of the warm 

 deep water inside the strait. In the temperature-salinity curve for this station it is seen 

 that the surface water has been warmed by the sun and considerably diluted. Between 

 the surface and a depth of 40 m. the salinity increases rapidly, and from 40 to 80 m. the 

 salinity increase is less rapid but the temperature decreases rapidly. Between 80 and 

 300 m. the salinity increases rapidly, but the temperature does not fall very much. This 

 layer between 80 and 300 m. represents the effect of vertical mixing in winter, with the 

 consequence that the salinity in this layer is less than at the corresponding depths in the 

 two other stations, and all evidence of a temperature inversion has been eliminated. 



The temperature-salinity curves for these three stations show a gradation from con- 

 ditions in the outside sea to conditions inside the Bransfield Strait: in the latter the 

 amount of warm deep water is greatly restricted, as is seen either by the small maximum 

 temperature of this layer at some stations, e.g. St. WS 384, or by the complete absence 

 of a temperature inversion at the majority of stations, e.g. St. WS 385. As a consequence 

 of the decreased amount of warm deep water inside the strait the level of the Antarctic 

 bottom water is much higher inside the strait than outside. 



The restricting influence of the submarine ridges is especially pronounced in the low 

 temperatures inside the strait below 300 m. In the Bransfield Strait only traces of the 

 warm deep water from outside are present, and this water in very reduced amount is 

 found mainly at the south-west end of the strait and at stations close to the south-east 

 coast of the South Shetland Islands (except in November 1929), where the extent of its 

 presence is shown by weak intermediate maxima in temperature. Farther towards the 

 eastern part of the strait nearly all thermal trace of the warm deep water is missing. 

 This is due to mixing with the highly saline and cold Antarctic water whose origin is the 

 Weddell Sea ; part of this water is carried round Joinville Island to flow across the strait 

 at its northern end, and some down it in a south-westerly direction on the Trinity 

 Peninsula side of the strait. The maximum temperature of the warm deep water, which 

 in the adjacent sea is found near the upper surface of this layer at approximately 500 m., 

 is situated inside the strait at least 100-200 m. nearer the surface. 



The bottom water from the deep ocean outside the strait cannot enter the Bransfield 

 Strait because of the submarine ridges. Even in the great depths of the Drake Passage 

 and the Weddell Sea the temperature never approaches the low value of — 1-72° C, 

 which has been found inside the Bransfield Strait at a depth of 1500 m. The bottom 

 water inside the strait is essentially formed within the strait. 



HORIZONTAL AND VERTICAL SECTIONS OF TEMPERATURE, 



SALINITY AND DENSITY 



APRIL 1927 



From the results obtained in April 1927 a more complicated system of water 

 layering was sometimes found than had hitherto been observed by us in the south- 

 west Atlantic south of the Antarctic convergence. Three layers of water are usually 



