PHYSICAL OCEANOGRAPHY OF THE GULF OF MAINE 



927 



summer (p. 588). The fact that the sm-face averages somewhat cooler along the coast 

 at that season, from Cape Cod to Cape Elizabeth, than a few miles offshore probably 

 reflects the cumulative effect of such upwellings following the prevailing southwesterly 



67- .40 I.M. 6,g" 



Portland 



Fig. 186.— DifEerence fn density between the surface and the 40-meter level in July and August for the several years of 



record, combined. Corrected for compression 



winds. No doubt this happens still more frequently there in winter, when northwest 

 gales are frequent, though it is not so easily recognizable then. In the opposite 

 side of the gulf the tendency is the reverse — i. e., the surface water is driven 

 in against the shore and sinks; and with vertical mixing by the tides so active that 



