The general pattern of the surface currents can be inferred from the distribution 

 of the water masses taken together with the dynamic topography and direct current 

 measurements. The currents obtained in this manner are shown in figure 7 for the north- 

 eastern Bering Sea and eastern Chukchi Sea during the late summer of 1949. 



The flow is predominantly northward from the region between St. Matthew and 

 St. Lawrence Islands to as far north as 70° N. The flow of the Alaskan. Coastal Water 

 close to the coast is very pronounced. In the Bering Sea, the current passing around the 

 east end of St. Lawrence Island and north to Bering Strait is somewhat strengthened 

 by outflow from Norton Sound and the Yukon River. The major current through Bering 

 Strait appears in the eastern half of the strait. 



In the Chukchi Sea, in addition to the coastal current a moderate flow entering 

 from the southwest appears along the northern side of the tongue of Siberian Coastal 

 Water. This flow probably contributes to the split in current occurring west of Pt. Hope 

 and Cape Lisburne. In this region one branch of the split current appears to proceed 

 northwest toward Herald Shoal and the other follows northeast along the Alaskan 

 Coast. North of 70° N, the predominant feature in the area surveyed is the eddy 

 between the coastal current and the Arctic drift with an indication of a weak south- 

 westward return of lower-salinity surface water in the northwestern part of the area. 



conclusions 



In the preceding sections the identification, distribution, and movements of the 

 water masses have been discussed with only slight reference made to their origin. 

 From the present available data, an hypothesis of development of the system is pro- 

 posed for consideration and further investigation. 



During the winter months the ice boundary progresses southward, not by current 

 drift or wind effect but because of the atmospheric cooling. Because of the high winds, 

 lack of run-off, and the freezing of the ice, a vertically uniform water mass probably 

 exists in late winter from the Chukchi Sea through Bering Strait and over the greater 

 part of the shallow Bering Sea. This water mass is then in equilibrium with the freezing 

 ice, which for water of salinity of 33.00 °/oo is a temperature of 28.8° F.* This is the 

 origin of the Deep Shelf Water. 



As the ice recedes in the spring, the winds continue mixing so that Ice Melt water 

 is dissipated except at the immediate ice boundary. However, the effects of surface 

 heating and solar radiation as spring progresses warm the surface layers of the water 

 mass, developing the Modified Shelf Water. 



At the same time the warmer coastal drainage progressively creates the Alaskan 

 Coastal Water near shore. The outflow from several rivers renews the water mass 

 downstream so that the identity or characteristics are maintained at least as far north- 

 ward along the Alaskan Coast as Cape Lisburne. The stations northeast of Cape 

 Lisburne indicated some deterioration of the Alaskan Coastal Water. 



The Intermediate Water appears to be largely a broad zone of mixing which 

 develops between the Modified Shelf Water and the Coastal Water. It first occurs 

 south of St. Lawrence Island off Cape Romanzof where it extends over a wide area, 



*An expedition aboard the USS BURTON ISLAND (AGB-1) in February 1951 observed vertically 

 uniform conditions in the region of the ice in the northeastern Bering Sea northward to the latitude of 

 64° 50'. Observed temperature was 28.9°F and salinity ranged from 31.8 °/ 00 to 33.4 °/ 00 depending 

 upon location. 



