PHYSICAL OCEANOGRAPHY OF THE GULF OF MAINE 



563 



Georges Bank, also; and the presence of a band of water cooler than its immediate 

 surroundings along the outer side of the latter bank and off Marthas Vineyard in sum- 

 mer (p. 608) suggests its influence. 



It is still an open question how far westward into the gulf the vernal warming 

 of the surface is retarded by this same agency. Even without its chilHng effect, the 

 surface probably would not warm as rapidly in the eastern side of the gulf as in the 

 western, because the heat received there from the sun is more rapidly dispersed down- 

 ward by more active vertical tidal stirring. Consequently, a slight west^east differ- 

 ential in surface temperatures, late in spring or early in summer, does not necessarily 



Fig. 32. — Normal rise in surface temperature from mid-April to mid-May. Ttie hatched area experiences cooling 



imply cold water from the eastward as its cause unless it reflects a corresponding 

 difference in the mean temperature of the upper 40 to 60 meters. 



Up to the present time we have found no positive thermal evidence of the Nova 

 Scotian water beyond the eastern arm of the basin (the situation of ice patrol station 

 No. 3, p. 997) ; and the temperature (salinity, too) of the gulf is so uniform from sum- 

 mer to summer that vernal chilling from this source is not to be expected farther west 

 than this, unless an exceptional spring may see a much greater inflow of cold water 

 from the east than usual past Cape Sable. 



