Figure 14.— Surface temperature ("C), spring 1963. (The 183- and 1,829-ni. depth contours are 

 shown.) 



(>7.2<^ C.) near the 1,829-m. depth contour 

 (fig. 16). 



Differences between temperatures during 

 spring and fall were most pronounced above 

 the halocline, in the zone affected by seasonal 

 heating. Significant changes also occurred, 

 however, within the lower zone which is not 

 influenced directly by the seasonal heating; 

 changes in circulation are implied. 



Although the gradient of the surface tem- 

 perature between northern Vancouver Island 

 and the Columbia River was the same during 

 each season, temperatures were generally 

 1.0° C. higher at each location during the fall 

 (fig. 17). The most pronounced changes were 

 near shore. During spring, warming was ap- 

 preciable only near the surface in the dilute 



water off the coast of Washington, but in the 

 fall the water was distinctly warmer over the 

 entire Continental Shelf than offshore. The 

 resulting temperature distribution shows a 

 tongue of warm water extending northward 

 along the coast and the maximum temperature 

 along any line normal to shore near the edge 

 of the Continental Shelf. 



Comparison of fall and spring conditions 

 along the same two vertical sections indicated 

 many differences and similarities with depth 

 and distance from shore. The most pronounced 

 differences were in the upper 70 m. In contrast 

 to the gradual decrease of temperature sea- 

 ward during spring was the presence of two 

 maxima during the fall — one at the surface 

 near the edge of the Continental Shelf and the 



GEOSTROPHIC CIRCULATION 



237 



