PHYSICAL OCEANOGRAPHY OF THE GULF OP MAINE 



791 



The eastern ends of the summer profiles along this general line confirm the evi- 

 dence of the charts to the effect that the flow of Nova Scotian water past Cape 

 Sable nearly or quite ceases befofe July, by the extremely abrupt transition in salin- 

 ity between the stations just to the west of the cape (32.4 to 32.8 per mille) and 

 those in its ofBng or just to the east of it (< 32 per mille). 



The western end of any summer profile along this line, whether for 1913 or for 

 1915 (fig. 154), is interesting chiefly for its demonstration that off Massachusetts 

 Bay water less saline than about 32.5 per mille occupies a cross section hardly less 

 extensive than in May (fig. 126), though with the isohaline for that value pointing to 

 some tendency for the fresher water to expand, seaward, over the salter. A rela- 

 tionship of this same sort also appears, as might be expected, on other profiles 

 running out normal to the coast line, at several locations between Cape Ann and the 

 Bay of Fundy, for the summers of 1912 and 1913 (Bigelow, 1914, figs. 30 to 32, 

 and Bigelow, 1915, figs. 49 to 51). 



Fig. 154.— Salinity profile running eastward across the gulf from the mouth of Massachusetts Bay (station 10306) to the offing 

 of Cape Sable (station 10312), August 31 to September 2, 1916 



The summer profiles also supplement the charts for the 100-meter level in making 

 clear the isolation of the sink off Gloucester (typical of all such sinks) by its barrier 

 rim, resulting in the vertical homogeneity of salinity below the level of the latter, 

 with a considerably lower value at the bottom of the sink than at an equal depth in 

 the basin outside, which is characteristic of this situation. 



The summer state of the water in the bowl inside Stellwagen Bank and in the 

 deep channels that give entrance to it on the north and south is developed by pro- 

 files crossing the mouth of Massachusetts Bay for August 31, 1912 (Bigelow, 1914, 

 fig. 33), July 19, 1916 (fig. 155), and August 22, 1922 (fig. 140). In the summers of 

 1916 and 1922 the saUne bottom water (>32 per mille) of this bowl was continuous 

 with the still higher salinities of the basin of the gulf outside via the floor of the 

 channel next Cape Ann, but was entirely cut off to the southward by Stellwagen 

 Bank. Consequently, any bottom drift that may have been taking place into the 

 bay at the time, or shortly previous, must have followed the northern route. 



