6 



The Chukotsk Sea 



I. SITUATION AND HISTORY OF EXPLORATION 



The Chukotsk Sea lies to the east of Wrangel Island as far as Cape Barrow and 

 is connected with the Pacific Ocean by the shallow, narrow Bering Strait. For 

 this reason its fauna is of special interest. 



The study of the fauna of the Chukotsk Sea began with the collections made 

 by A. Stuxberg, of the O. Nordenskjold expedition on the Vega (1878-79). 

 The Soviet period — especially the expedition of the icebreaker F. Lithke 

 (1929, 1934), the Pacific Ocean expedition of the State Hydrological Institute 

 (1932-33), the expeditions of the Chelyuskin (1933, 1934) and finally in 1935 

 that of the icebreaker Krassin* — has been most fruitful as regards the ex- 

 ploration of the Chukotsk Sea. 



II. PHYSICAL GEOGRAPHY 



Size and bottom topography 



The Chukotsk Sea (Fig. Ill) is fairly large (582,000 km 2 ), but very shallow, 

 being for the most part less than 50 m deep. Its volume is 51,000 km 3 , its 

 average depth 86 m, and its greatest depth 180 m. 



A trench with depths of more than 50 m (the average depth of the Sea 

 being about 45 m) enters the Chukotsk Sea to the east of Wrangel Island. This 

 trench at first runs towards the Chukotsk Peninsula and then eastwards along 

 it. North of 73° 30' N latitude the bottom begins to slope down steeply into 

 the greater depths of the Arctic basin. The floor of the Bering Strait and of the 

 Herald Shoal is hard (sand, gravel, pebble, rock) ; the rest of the bottom con- 

 sists of silty sands and clayey mud. 



Currents 



A fairly warm, strong current (Fig. Ill) enters the Chukotsk Sea through the 

 Bering Strait, travelling north along the eastern boundaries of the Sea ; north 

 of Cape Hope it divides into two branches — a northeastern and a north- 

 western. A cold current leaving De Long Sound moves southeast along the 

 coast of the Chukotsk Peninsula, part of it entering the Bering Strait, but its 

 main mass turning back into the southern part of the Sea. In general the move- 

 ment through the Bering Strait is that of the Pacific Ocean waters into the 

 Chukotsk Sea, and only to a very small extent a flow of the Chukotsk waters 

 to the south. 



Temperature and salinity 



It is evident from the range of the bottom temperatures in August (Fig. 112) 



that the Chukotsk Sea waters are only very slightly warmed. The sea conditions 



* In our further exposition we shall use the detailed summary of P. Ushakov (1945). 



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