ESTUARINE MODEL OF SUB-ARCTIC PACIFIC OCEAN 435 



In the earlier study, Tully (1958) showed that the rate of 

 upward transport, — W, of sea water through the lower limit, L, 

 of the halocline was 



1 — C 



where C Is the fresh water fraction of the upper zone and halocline, 

 1 — C is the sea water fraction, and Q Is the rate of input of fresh 

 water. From Fig. 6, the fresh water fraction C is 2 to 5%, an 

 average of about 3%. The rate of input Is about 0.6 m per year 

 over the area. Hence the average upward velocity must be about 

 20 + 10 m per year over the area. 



Circulation and Transport 



Obviously there are other transport mechanisms operating to 

 create the circulation In the sub-Arctic Pacific Ocean, for example, 

 wind stress (Munk, 1950). In this region, from the confluence of 

 the Kuroshio and Oyashio off the coast of Japan, the warm and 

 cold waters move side by side toward America in the West Wind 

 Drift. The surface gradient of temperature across the flow Is called 

 the Polar Front. Off the American coast the waters divide. Part 

 turns south to form the California Current. The remainder turns 

 northward and flows around the Gulf of Alaska. This water 

 returns westward, close along the Aleutian Islands and is pro- 

 gressively dissipated into the Bering Sea. Most of this eventually 

 joins the southward flow along Kamchatka. This is the origin of 

 Oyashio and completes the circulation. Throughout the course of 

 this flow an excess of fresh water is added to the surface and 

 incorporated Into the water masses. Hence this mixed water must 

 eventually be transported to the sub-Tropics where the fresh water 

 can be removed by evaporation, or to the Arctic Ocean. 



Comparison of the limits of sub-Arctic structure (Figs. 3 and 4) 

 with the circulation pattern (Fig. 7) shows that all the sub-Tropic 

 water and part of the sub-Arctic water enter the California Current. 

 A small part of the water in the Bering Sea is lost through Bering 

 Strait to the Arctic Ocean (Saur et al., 1954; Bloom, 1956). These 

 define two regions of outflow of mixed fresh and sea water. 



