The kara sea 225 



Side by side with the surface layer, with its considerable loss of salinity and 

 its summer rise in temperature, and with the deep, highly saline waters of 

 practically constant low temperature, there is in the Kara Sea in the summer a 

 definite intermediate cold layer 50 to 100 m deep. This layer is formed by the 

 sinking of the cold surface waters, which in the previous winter had been 

 considerably cooled and have become much more saline as a result of the 

 formation of an ice cover (Figs. 94 and 95). The presence of a thick cold inter- 

 mediate layer is an indication of a comparatively weak vertical circulation. 



Like all the marginal seas, more or less cut off from the open ocean, with 

 a large inflow of river water, the Kara Sea is characterized in its surface 

 layer by unstable saline conditions which depend on the amount of river 

 water. As an example of this one may mention the differences in the tempera- 

 ture and saline conditions of the sea in 1927 and 1945, given in Figs. 94 and 

 95. In 1945 the inflow of river water into the Kara Sea was only about two 

 thirds of the many years average amount and the salinity of the surface sea 

 waters was found to be considerably higher. However, as can be seen from 

 the cross sections, the deep water retained its salinity. A general warming 

 up was equally clearly perceptible. Low temperature ( — 1-6° to — 1-7°) was re- 

 tained only in the deepest layer. The surface layers were warmed most of all. 

 In the summer of 1945 the Kara Sea was completely free of ice for several 

 months. 



In summer the dilution of the surface layer prevents vertical circulation ; 

 in winter, however, it causes a further increase of ice formation. As a result 

 salt water, formed on the surface, sinks into the depths. In winter the tempera- 

 ture of the surface layers of the Kara Sea is mostly — 1-6° to — 1-8°, while its 

 salinity is 34% and higher. This feature of the hydrological conditions in the 

 Kara Sea is similar to that of the White Sea. 



Atlantic waters of the intermediate layer of the Arctic basin (salinity up to 

 35% ; temperature up to 2-5°) and the much colder waters of the same salinity 

 lying beneath them, enter the northern part of the Sea at depths of 1 50 to 

 300 m. 



Ice frequently begins to form in the Kara Sea as early as September, while 

 proper melting only begins in June. The summer is short and cold. The central 

 part of the Sea is not covered with solid ice, even in winter time, but wide firm 

 ice belts and large stranded hummocks are formed at the shores. 



The general character of the summer ranges of temperature and salinity 

 throughout the Kara Sea waters in 1945 is given in the hydrological cross 

 section in Fig. 96. As may be seen from the second diagram, the northern part 

 of the Sea is warmed more than the central part, while the southern one is 

 under the influence of the warmer waters entering it from the Barents Sea 

 and of the local coastal ones. 



The hydrological conditions of the Kara Sea are most complicated owing 

 to the entrance of deep currents of warmer and more saline Atlantic waters 

 into it from the north, partly from the Barents Sea and partly directly from 

 the Arctic basin ; to the exchange of water through the Kara Gates with the 

 Pechora region of the Barents Sea, and with the Laptev Sea in the east ; to 

 the inflow of huge masses of river water from the south ; and finally to sharply 





