Ocean Temperatures along the West Coast of North America. 283 



4. The coldest water is located about 809 miles south of Sitka in 

 the summer time, and areas of alternately warm and cold water are 

 distributed in an irregular manner all along the coast. But from each 

 of the previous theories, owing to the continual increase in the hea- 

 ting effect of the sun toward the south, a continuous rise in tempera- 

 ture would accompany a decrease of latitude. Therefore the low tem- 

 perature must result from an up welling of cold bottom water from the 

 adjacent ocean depths. A general eastward drift of the ocean water 

 extending to the bottom is assumed to result from the continued ac- 

 tion of the winds, consequently the cold bottom water is driven up 

 the continental slope, most of it reaching the surface at Cape Mendo- 

 cino (the coldest region). The irregularities in temperature distribution 

 are due to the effects of submarine valleys and differences in the 

 slope of the ocean bottom. 



The above theories were based on hypothetical causes, which in 

 some cases were not verified except by the general qualitative agree- 

 ment of the deductions with the particular observations considered, 

 and the theory of oceanic circulation proposed in 1878 by Zoppritz 

 was widely used. No attempt was made to explain the seasonal 

 fluctuation. 



Before going on with . the conclusions regarding the Pacific coast 

 region it will be necessary to consider general theories of oceanic cir- 

 culation. A recent one due to Ekman differs from that of Zoppritz, 

 in that no assumption as to regular flow in plane layers is used as 

 a basis, but a virtual value of the coefficient of viscosity, allowing for 

 the actual turbulent motion of the water is used, and the deflecting 

 force due to earth's rotation is also introduced. Many results of 

 Zoppritz 's theory are inconsistent with observations, while those of 

 Ekman's theory are in harmony with experience. Most of the results 

 of the two theories are entirely different. 



From Ekman's theory it follows that there must be an upwelling 

 of the cold bottom water along most of the coast of North America 

 owing to the action of the observed winds, and in the present paper, 

 assuming the low temperature to be due entirely to cold bottom water 

 upwelling and mixing with the surface water a theoretical formula 

 was derived by which the abnormally low temperatures of any region 

 could be computed for each month of the year. A very satisfactory 

 agreement with observations was obtained, tho the temperature reduc- 

 tion below the normal varied from to 8. 



In general the theory shows that the area affected and the mag- 



