BIGELOW: EXPLORATIONS OF THE COAST WATERS. 231 



to be gradually reestablished by the warming and freshening of the 

 surface in spring (1914b). And density is probably comparatively 

 uniform, horizontally, over the Gulf as a whole during the cold months, 

 though our records for winter are limited to the neighborhood of Cape 

 Ann. In spring, however, the inrush of land water along the northern 

 and western shores, together with the entrance of Cabot Current 

 water around Cape Sable (p. 224) lowers the surface density on the 

 east and west sides of the Gulf much faster than the more gradual drop 

 in salinity offshore, plus solar warming, lowers that of its center, as 

 illustrated by a profile across the Gulf in May (Fig. 77). Particularly 

 instructive, for its bearing on circulation (p. 242), is the fact that the 

 cool, fresh water off Nova Scotia and on German Bank, the visible 

 effect of the Cabot Current (p. 235), is lighter than the water it meets 

 in the Eastern Basin of the Gulf, in spite of the higher temperature 

 of the latter, hence floats upon it, instead of sinking into the Basin. 

 Even in May, the density of the bottom water of the Gulf is very 

 uniform horizontally, west to east. And during the summer, surface 

 density is gradually equalized until, by August a layer of water lighter 

 than 1.026, some 70 meters thick, extends right across the Gulf 

 (1914a, 1915). 



Annual hydrographic variations in the Gulf of Maine. 



The differences between the summers of 1912 and 1913 have already 

 been discussed (1915, p. 246); in brief, the Gulf was colder and fresher 

 in its eastern, warmer, but of about the same s.alinity in its western 

 half in 1913 than in 1912. 



The observations for 1913 and 1914 were made at the same season 

 (middle of August); hence are directly comparable. But in com- 

 paring the records for 1915 with those for the preceding 3^ears, allow- 

 ance must be made for seasonal change, the earlier observations 

 having been taken in the middle of August, the most nearly compar- 

 able set for 1915 some three weeks later (September 1-19). And as 

 pointed out (1914a), it is during just this period that the surface, in the 

 western side of the Gulf, begins to cool, whereas on the eastern side, 

 surface warming still continues, though the salinity of the eastern 

 basin apparently decreases (p. 225). 



On the surface the distribution of temperature was practically the 

 same, but the absolute values were everywhere 5°-3° higher, in 1914 

 than in 1913 (Fig. 1; 1915, fig. 1), the only exception being locally, 

 north of Cape Ann. 



