CHUKCHI SEA 



NORTHWIND 8-16 AUG 1963 



Where does this water come from? One possibiUty 

 hypothesized initially was that the source of the water mass 

 may be the pycnochne layer of the Arctic Ocean. The focal 

 areaeast of Wrangel Island is the head of the Herald Submarine 

 Canyon, which indents the Chukchi Shelf near Herald Island 

 (see Fig. 1). The concept was that Arctic Ocean water might 

 flow in-canyon along the bottom onto the shelf, as it does in 

 Barrow Canyon on the eastern side of the Chukchi (Mountain 

 et al., 1976). This hypothesis can be ruled out because the 

 phosphate content of the Siberian Coastal water mass is much 

 too low to be Arctic Ocean water. 



The most likely hypothesis is that the water mass is of 

 Bering Sea origin. It is Bering Shelf water that enters the 

 Chukchi Sea during fall and winter, where its salinities are 

 enhanced through ice formation. Then the following summer 

 the water is recirculated throughout the southern Chukchi Sea 

 via the Siberian Coastal Current. Two observations in support 

 of this hypothesis are: 7. the '"O values of the water are 

 precisely those of Bering Shelf water (Fig. 8); and2. the focal 

 point of highest salinities east of Wrangel Island is an area 

 where the least amount of ice formation in winter is required to 

 enhance salinities to the requisite -33.5 (Fig. 18). 



Fig. 16. T/S correlations for the Mir//iu(>(i/data. Individual lines are all stations 

 in the Chukchi Sea; stations from Bering Strait and the East-Siberian 

 Sea are enclosed in envelopes. Stations from Long Strait ( marked, see 

 Fig. \5) have the highest S values of all. 



13V -SO' 



Fig. 1 8. The amount of ice growth required to raise the salinity of water columns 

 to 3.^.5 "/(x) . Notice the area of minimum necessary ice growth 

 coincides with the area of highest salinities near Wrangel Island and 

 Herald Shoal (from Aagaard, Coachman & Carmack, 1981 ). 



Fig. 17. Confirmation that the source of high salinity (and high nutrient) water 

 is near Wrangel Island and Herald Shoal to its east side. Data from 

 three cruises: (upper) Miiiid. 1922; (lower lelll Nurllmiiid. 1962; 

 (lower right) Osharn Maru, 1972. 



With this hypothesis, the relatively high nutrient 

 concentrations are supplied by the rich Bering Shelf water in 

 winter that are not utilized or affected by freezing, so are 

 available to fuel the Chukchi Sea end of the ecosystem the next 

 summer. The circulation, insofar as it is known (Fig. 19). fits 

 in with this hypothesis, though there must be more southerly 

 components of flow in the western Chukchi, southwest of 

 Herald Shoal, than indicated in the schematic depiction. The 

 presence of the highest salinities near Herald Shoal, and 

 particularly to its west and southwest, is not coincidence; the 

 shoal water is undoubtably important in providing the most 

 effective environment for salinity enhancement by freezing. 



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