tween oceanic and coastal water, and the ef- 

 fects of dilution have been shown to extend 

 over several hundred kilometers from shore 

 (Favorite, 1961). Sharp gradients, or fronts, 

 found closer to shore, however, are more in- 

 teresting and much more complex. 



The distribution of surface salinity during 

 spring showed that the 32.5%o isohaline ap- 

 proached within 160 km. of shore off the coast 

 of Washington, but the most significant fea- 

 ture was the front associated with the 32.0%o 

 isohaline (fig. 9). The controversy regarding 

 the precise definition of the term front in 

 oceanographic usage has been discussed by 

 Griffiths (1965). Front is used here in the 

 sense that Cromwell and Reid (1956) defined 

 the term, "... a band along the sea surface 

 across which the density changes abruptly." 

 The change of surface temperature near the 

 front was not appreciable compared with the 

 salinity change ; thus the density change at 

 the front was dominated by the relatively 

 sharp decrease in surface salinity. Although no 

 particular isohaline appeared to define the 

 exact extent of the front throughout the area, 

 gross changes in the position of the front may 

 be seen by tracing, the extent of the 32.0%o 

 isohaline. The largest gradient of surface 

 salinity was about 80 km. from shore near lat. 

 46^ N. where the front was apparently being 

 maintained by effluent less was 22%o from 

 the Columbia River. The maximum seaward 

 extent of the 32.0%o isohaline was 112 km. 

 near lat. 47° N. ; at lat. 48° N. it had decreased 

 to 64 km., and all along the coast of Vancouver 

 Island it was confined to within 48 km. of 

 shore. It is not clear whether the large tongue 

 of dilute water off the central coast of Wash- 

 ington was a remnant of water from the Co- 

 lumbia River which had proceeded north along 

 the coast during the winter or if it came di- 

 rectly from the Strait of Juan de Fuca. A 

 patch of relatively high salinity water 

 (> 32.2%o) about 11 km. seaward of Hoh 

 Head indicated an area of local upwelling. 



A vertical section of salinity extending sea- 

 ward from Willapa Bay illustrates the major 

 changes in salinity with depth and distance 

 from shore during spring (fig. 10). Dilute 

 water of less than 32.0%o in which the iso- 



43 STATION NO 

 O 



-ZpOO 



Figure 10. — Vertical sections of salinity (%„), to 

 200 m. and to 2,500 m., along Willapa Bay line, 

 spring 1963. 



lines were closely spaced, appeared to protrude 

 seaward in the form of a tongue. Although 

 the 32.0%<. isohaline that occurred at the 

 leading edge of this tongue underwent large 

 fluctuations in its seaward extent along the 

 coast, the nearly constant depth of the 

 32.0%o isohaline near shore shows that the 



GEOSTROPHIC CIRCULATION 



233 



