Figure 16.— Temperature ("C.) at 200 m., spring 1963. (The 183- and 1,829-ni. depth contours 

 are shown.) 



ing fall — 7.6° C. Although this increase in 

 temperature between spring and fall was 

 slight, it may be significant compared with the 

 small range of values at 200 m. The associa- 

 tion of the warm water near the coast of north- 

 ern Vancouver Island with the lowest salinity 

 values implied a local convergence. Offshore 

 the cold water was also of low salinity. The 

 warm water off the coast of Washington near 

 the 1,829-m. depth contour, however, was as- 

 sociated with the high-salinity ridge; a sig- 

 nificant change in water mass is indicated. 



DISSOLVED OXYGEN 



The distribution of dissolved oxygen during 

 the spring was obtained only over the con- 

 tinental terrace between the depths of 55 m. 



and 1,829 m. As with the distributions of tem- 

 perature and salinity, the sharpest vertical 

 gradient occurred within the halocline. Below 

 the saturated or mixed layer, about 50 m. deep, 

 values decreased sharply to about 300 m. Below 

 300 m., concentrations decreased gradually to a 

 minimum near 900 m., below which values 

 gradually increased toward the bottom. 



Samples obtained at each station during the 

 fall permit comparison of conditions near 

 shore and offshore. The vertical section off 

 Willapa Bay shows the complex distribution of 

 dissolved oxygen in the upper 300 m. (fig. 19). 

 Deeper isolines were relatively level and the 

 oxygen minimum near 900 m. extended off- 

 shore without significant change in depth. The 

 isolines within the upper 300 m. usually fol- 



GEOSTROPHIC CIRCULATION 



239 



