major effect of the dilution off the coast of 

 Washinglon was limited to the upper 30 to 40 

 m. Offshore, the three vertical zones charac- 

 teristic of the Subarctic Region were present; 

 although the boundaries between zones gener- 

 ally rose toward shore, the halocline and lower 

 zone could be traced continuously inshore until 

 they ended at the continental terrace. 



Tully and Barber (1960) suggested that 

 across the boundary of the halocline-lower 

 zone 33.8 ± 0.1%=, only upward transfer of 

 water existed ; thus the depth of this surface 

 forms the ultimate limit of downward transfer 

 of water from the surface. Changes in prop- 

 erties below this surface are, therefore, pri- 

 marily due to advection, not directly influenced 

 by seasonal changes near the surface. The 

 33.8%o surface was about 170 m. deep off- 



shore but rose to about 130 m. near the 183-m. 

 depth contour. 



A horizontal section of salinity at 200 m. 

 during spring showed uniform values of salin- 

 ity just below the halocline; the range was 

 from about 33.86%o to 33.93% (fig. 11) 

 — a marked contrast to the i-ange of surface 

 salinity, 22.0%o to 32.5%o. A second im- 

 portant feature was the tongue of relatively 

 high salinity (> 33.92%o) which appeared 

 to point northward near the 1,829-m. depth 

 contour off Willapa Bay. Although many of 

 the features in the coastal area during the fall 

 were similar to those during the preceding 

 spring, important changes occurred near the 

 surface between spring and fall. The salinity 

 front was consistently nearer shore, 48 km. to 

 64 km. (fig. 12). The tongue of dilute water 



234 



isrw. oo* iM' i2a" liT izi' i25* 



Figure 11. — Salinity (%„) at 200 m., spring 1963. (The 18.3- and 1,829-m. depth contours are shown.) 



U.S. FISH AND WILDLIFE SERVICE 



