lated geostrophic currents. The following items 

 are discussed : features of the distributions of 

 salinity, temperature, and dissolved oxygen ; 

 changes in these properties near the bottom 

 along the continental terrace ; and water mass 

 movements implied by temperature-salinity 

 relationships. 



SALINITY 



Throughout most of the Subarctic Region, 

 the salinity structure consists of three distinct 

 permanent zones: (1) an isohaline upper zone, 

 which extends from the surface to about 100 

 m. ; (2) a halocline, in which the salinity in- 

 creases about l%o between 100 and 200 m.; 

 and (3) a lower zone, in which the salinity 

 gradually increases with depth. The mechan- 

 ism for the maintenance of this structure was 



discussed by Dodimead et al. (1963). 



Perhaps the most striking changes in the 

 distribution of properties within the coastal 

 areas occur in the salinity distribution in the 

 upper zone and are due to the intrusions of 

 fresh-water runoff from coastal rivers. Various 

 authors have attempted to distinguish oceanic 

 and coastal water on the basis of the salinity 

 distribution near the surface. In the North 

 Pacific Ocean, Doe (1955) used the 32.5%o 

 isohaline as the boundary between offshore and 

 coastal water masses in the upper zone; Dodi- 

 mead et al. (1963) defined the extent of a 

 coastal domain by the 32.4%. isohaline; and 

 Budinger et al. (1964) suggested the Columbia 

 River effluent could be traced by salinities less 

 than 32.5°oo. Good agreement has thus been 

 reached concerning a definable boundary be- 



FlGURE 9.— Surface salinity (%.), spring 1963. (The 18.3- and 1,829-m. depth contours are shown.) 

 232 U.S. FISH AND WILDLIFE SERVICE 



