SURFACE WATERS OFF THE CANADIAN PACIFIC COAST 577 



it cannot be determined whether there are significant differences be- 

 tween them and the present surveys. 



However, it is evident that there are important differences be- 

 tween the conditions observed in 1950 and 1951 (Figure 5). The cal- 

 culated gradients and isentropic analyses suggest that the division of 

 the Sub- Arctic Current was further south in 1951. An attempt was 

 made to relate this difference with the atmospheric pressure systems 

 in the area. However, these showed that the division between the winds 

 with a southerly component and those with a residual northerly com- 

 ponent was further south in 1950. Thus the differences between these 

 two years observations are not immediately apparent in the wind fields. 



Considering the character and magnitude of the system (Figure 8) 

 it may be anticipated that the division of currents will shift north and 

 south by several degrees of latitude from year to year. Such changes 

 are small, but their effect is enormous in the strategic area off tlie Bri- 

 tish Columbia coast. It cannot be said that the early data showing a 

 southward flow near the shore are inconsistent with the present data 

 indicating a northward movement further offshore, or that the change 

 of character of the currents and properties from year to year are ano- 

 malous. The present problem is to determine the cause, sequence, and 

 nature of these changes. 



References 



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 from Dutch Harbor, Alaska to the Strait of Juan de Fuca, and from 

 the Strait of Juan de Fuca to Hawaii. Univ. of Wash. Publ. in Ocea- 

 nography, 3 (3) 81-103, 1940. 



IGELSRUD, I., R. J. Robinson and T. G. Thompson. The distribution of phos- 

 phates in the sea water of the northeast Pacific. U7iiv. of Wash. Publ. in 

 Oceanogra2:hy, 3 (1) 1-34, 1936. 



McEwen, G. F., T. G. Thompson and R. Van Cleve. Hydrogi-aphic sections 

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Montgomery, R. B. Circulation in the upper layers of the southern north 

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PiCKARD, G. L. and D. C. McLeod. The seasonal variation of the tempera- 

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ROSSBY, C. G. Dynamics of steady ocean currents in the light of experimental 

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Scripps Institution of Oceanography. Physical and chemical data, Cruise 17, 

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