PHYSICAL OCEANOGEAPHY OF THE GULF OF MAINE 



735 



southeastern slope of Georges Bank, obliterating the fresher pool that had occupied 

 that situation in March. 



On the other hand the water more saline than 34 per mille that had occupied the 

 eastern side of the Eastern Channel in March had sunk deeper than 100 meters by 

 mid-April, with a corresponding decrease in temperature (p. 553). 



This general and rather complex seasonal alteration is illustrated more graphi- 

 cally in profile by the flooding of the entire basin with water more saline than 34 

 per mille, at depths greater than 140 to 160 meters, from March to April, on a Une 



Fig. 113. — Vertical distribution of salinity in tlie center of the gulf near Cashes Ledge. A, March 2, 

 1920 (station 20C.i2); B, April 16, 1920 (station 20114); C, May 5, 1915 (station 10268); D, Septem- 

 ber 1, 1916 (station 10308) 



running southward from Mount Desert (fig. 117). This was accompanied by a flat- 

 tening out of the undulations that had marked the upper boundary of the bottom layer 

 of high salinity in March (p. 717) , the isohalines for 33 to 33.5 per mUle sinking in the 

 eastern side of the basin and rising in the western. 



However, the level where the salinity altered most rapidly with increasing depth 

 remained approximately constant in the basin from March to April in 1920, center- 

 ing at about 150 meters; the limits of salinity within which the gradient was most 

 rapid (33 to 33.5 per mille) also remained constant, and the banking up of the saltest 

 water of the basin (34.5 per mille) against the slope of German Bank persisted. 



