SURFACE WATERS OFF THE CANADIAN PACIFIC COAST 575 



water to the coastal region because oi the offshore component of the 

 suTmner winds. This seaward transport is evidently greater than the 

 supply from runoff so that there is a degi-ee of upwelling. This results 

 in a band of cold water along the coast, which would be as saline as the 

 California coastal water, if it were not diluted by the great summer 

 runoff. 



In the Avinter the prevailing southeast winds impart an onshore 

 component to the motion, the light water is confined in a narrow region 

 close to the coast, and the surface waters are depressed. This is evi- 

 denced in the accumulation of low salinity -^varmer water along the 

 coast at this time. The seasonal effect is noticeable here in that the 

 coastal water, although warmer than that to seaward, is colder than 

 during the summer. 



Origins and Circulation of the Water 



The general circulation system of the north Pacific Ocean (Figure 

 7) has long been established by the Pilot Charts of the U.S. Hydrograph- 

 ic Office. The west wind current, called the Sub-Arctic Current by 

 Sverdrup (1942) is the Avind driven drift of surface water eastward 

 across the Pacific Ocean betAveen Latitudes 40^ and 50° N. As this cur- 

 rent approaches the coast of North America it divides. Part turns north 

 to form the Alaska Gyral, and part tinns south to form the California 

 Current. 



The Marine Life Research Program from Scripps Institution of 

 Oceanography has been studying the California Current in a series of 

 near-monthly cruises since 1949. Fortunately their Cruise 17 coincided 

 with the August 1950 survey and it was possible to combine the dynamic 

 charts as shown in Figure 8. This chart covers an enormous area, and 

 is the first dynamic picture of the current system off the North Ameri- 

 can coast. It is a spectacular confirmation of the previous conclusions 

 from the Pilot Charts. 



It is regretted that the other surveys by both agencies were not co- 

 ordinated more closely so that a seasonal, and annual series of such 

 diagiams could have been prepared. However, this example shows the 

 position of the area of the present studies in relation to the whole cur- 

 rent system, and allows the interpretation of the observations on a 

 broad basis. 



Evidently the area off the coast of British Columbia is in the region 

 of the divergence. Because of this, it is a region of eddies, or slow 

 and indefinite currents. Furthermore, it is extremely sensitive to small 

 changes in the route of the trans-ocean current. It may be subject to 



