fluence of seasonal processes (Tully and Bar- 

 ber, 1960). During spring the directions of 

 geostrophic flow at 200 m. and at the surface 

 were nearly identical (fig. 4). An exception 

 occurred near lat. 47° N., where water on the 

 Continental Slope veered more sharply offshore 

 than did the surface water. The deeper flow 

 followed the 1.829-m. (1,000-fathom) depth 

 contour and appeared to be influenced by the 

 local bottom topography. The maximum cur- 

 rent of 10 cm. /sec. was at 200 m., whereas the 

 surface flow was 6 cm. /sec. This condition is 

 contrary to the characteristic decrease in speed 

 with depth throughout most of the Subarctic 

 Region and occurred only in this one area off 

 the coast of Washington. 



Geostrophic currents at 200 m. during fall 

 also followed closely the direction of the sur- 

 face currents (fig. 5) . The speed at 200 m. was 

 generally one-half that of the surface current 

 north of lat. 48° N., but speeds significantly 

 greater than the surface flow were again pres- 

 ent off Washington. The speed of the pro- 

 nounced anticyclonic eddy just south of lat. 48° 

 N. near the 1,829-m. depth contour was 15 

 cm. /sec, at least three times the speed at the 

 surface. 



When Dodimead et al. (1963) showed the 

 California Undercurrent flowing northward 

 below 200 m., the surface water flowed south, 

 opposing the Undercurrent. Because there was 

 no southerly surface flow during the spring and 

 fall of 1963, this apparent reversal did not 

 exist ; but if the surface current was the slow- 

 er, the Undercurrent would be evident as a 

 relative maximum at 200 m. in the velocity 

 profile. The vertical distribution of velocity in 

 the upper 1,500 m. during the fall, seaward 

 from Willapa Bay, Hoh Head, and Esperanza 

 Inlet, showed an area within 165 to 220 km. of 

 the Washington coast in which pronounced 

 maxima in the velocity did occur between 

 depths of 200 m. and 300 m. (fig. 6) . The direc- 

 tion of flow in adjacent maxima opposed each 

 other, apparently forming eddies. The resultant 

 current across any line normal to the coast of 

 Washington, although northward, was very 

 small. Volume transport calculations indicate 

 the magnitude of the net flow. 



FULL 1963 



64 70 71 72 73 STATION NO 







■ipoo; 



I30'W. 128° 126' 124" 



51 34 33 32 31 5T1TI0N NO 



16 17 18 19 20 15 14 13 1211 STATION NO 



Figure 6. — Vertical sections of geostrophic velocity 

 (cm. /sec.) relative to 1,500 db. seaward from Willapa 

 Bay, Hoh Head, and Esperanza Inlet, fall 1963. 

 (Light shading indicates regions of northward flow.) 



VOLUME TRANSPORT 

 Volume transports are calculated by inte- 

 grating the geostrophic currents throughout 

 the water column (Sverdrup et al., 1942). The 

 volume transports indicate the resultant rela- 

 tive flow through the selected cross-sectional 

 area, and are, therefore, a more reliable repre- 

 sentation of the net flow in an area than a 

 chart of the geostrophic currents at a par- 

 ticular depth. In the previous section on geo- 

 strophic currents, I pointed out that surface 

 Ekman currents which were neglected may be 

 in the same order of magnitude as the surface 

 geostrophic velocities. In terms of the net 

 transport in this coastal area during spring 



GEOSTROPHIC CIRCULATION 



229 



