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SCHEMATIC DIAGRAM OF 

 UPPER ZONE DOMAINS 



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Figure 2. — Diagram of upper zone domains in the Subarctic Pacific Region (after Dodimead, Favorite, and 



Hirano, 1963). 



through passes between the islands. To distin- 

 guish the Coastal from Alaskan Stream Domains, 

 coastal water was arbitrarily defined by sui'face 

 salinities greater than 32.9'-,',. The Alaskan 

 Stream, described in detail by Favorite (1967), 

 flows westward out of the Gulf of Alaska with 

 velocities as high as 100 cm/sec. It is diluted 

 by runoff from Alaska and can be detected by 

 low salinity (less than S2.6'/t() at the surface. 

 The Central Subarctic Domain is an area of 

 weak and variable currents bounded on the north 

 by the Alaskan Stream and on the south by the 

 Subarctic Current, which flows eastward at ve- 

 locities between 5 and 20 cm/sec (McAlister 

 et al., 1970) . The Subarctic Current separates 

 the Central Subarctic Domain from the Tran- 

 sitional Domain, which extends southward as 

 far as the northern boundary of the Subtropical 

 Region and is also an area of weak eastward 

 flow. The nomenclature given by McAlister et al. 



(1970) was slightly diff'erent from that applied 

 to the upper zone domains of Dodimead et al. 



(1963), but it was based in part on features 



below the upper zone. For purposes of the 

 present paper, the definitions of the upper zone 

 domains as given in Dodimead et al. (1963) were 

 used; the Subarctic Current, which originates 

 in the Western Subarctic Domain, was thus in- 

 cluded in the Central Subarctic Domain. 



The Transitional Domain has been further di- 

 vided into two areas (T-1 and T-2) on the basis 

 of the salinity in the upper 50 m. The division 

 between areas T-1 and T-2 was set in August 

 1967 at lat 47° N, where surface salinity was a 

 maximum and decreased to the north and to the 

 south at least as far as lat 46° N. The Transi- 

 tional Domain was also divided in September 

 1966, when the northern area (T-1) extended 

 from lat 47°05' N to a relatively sharp hori- 

 zontal salinity gradient at lat 43°35' N. The 

 southern area (T-2) extended to lat 40°45' N, 

 where the boundary between transitional and 

 subtropical waters was found. These divisions 

 of the Transitional Domain are somewhat ar- 

 bitrary but tend to be corroborated by biological 

 and chemical characteristics. 



599 



