PHYSICAL OCEANOGKAPHY OP THE GULF OF MAINE 

 Salinity on the boltom of the trough, June, 1915. 



763 



The fact that the whole trough of the gulf was nearly as saline in the last half 

 of June, 1915, as we found it in April, 1920 (p. 737), suggest a recovery of the indraft 

 of slope water during the last half of May and first days of summer; but if such 

 a recovery actually took place in 1915 it seems soon to have slackened again, judging 

 from the rather abrupt transition from higher salinities in the Eastern Channe 

 to lower ones just within the basin of the gulf recorded during the third week of 

 that June (see the preceding tables) . 



The expansions and contractions of 34 per mille water over the floor of the gulf, 

 and the depth at which its upper limit lies below the surface of the water at any 

 given time, more clearly reflect the recent activity of the indraft through the East- 

 ern Channel than does the distribution of salinity at any given level in the water. 



In April, 1920, water as salt as this flooded the bottom of both arms of the 

 basin, rising up to within about 140 to 175 meters of the surface along the eastern 

 slope of the gulf (fig. 118). In June, 1915, however, 34 per mille water was confined 

 to the southeastern corner of the basin (station 10298) close to the entrance of the 

 Eastern Channel. 



SALINITY IN JULY AND AUGUST 



SURFACE 



If the readings taken in the western side of the gulf in July of 1912, 1913, and 

 1916 represent the normal succession to the June state of 1915 and 1925 (just 

 described) , the surface of this part of the area suffers a second freshening from 32 to 

 32.5per mille in June to 31.4 to 31.9 per mille in July, but with little or no change from 

 the one month to the next along the coast of Maine (31.5 to 31.8 per mille in July as 

 well as in June) . If this represents the regular seasonal progression it probably reflects 

 the anticlockwise surface drift, carrying the discharges of the eastern rivers around the 

 gulf to the Massachusetts Bay region a month or more after their freshening effect has 

 been entirely obscured off the coast of Maine by tidal stirrings. This explanation is 

 supported by the fact that the July values for the surface of the bay were lowest in 

 1916 (30.5 to 31.2 per mille), when a very tardy spring, with unusually heavy snow- 

 fall, would make a seasonal sucession of this sort the most likely. The surface water 

 of the western part of the basin of the gulf, in the offing of Cape Ann, has proved 

 less saline in every August of record (1913, 1914, and 1915) than it is in May (p. 741) 

 or June (p. 756), in the following seasonal sequence and for the same reason: 



Surface salinity, western basin 



Date 



May 4, 1916 .. 

 June 26, 1915 

 July 15, 1912 . 



Station 



10267 

 10299 

 10007 



Salinity 



Per mille 

 33.03 

 32.60 

 31.62 



Date 



Aug. 9, 1913 . 

 Aug. 22, 1914 

 Aug. 31, 1915 . 



station 



1008S 

 10254 

 10307 



Salinity 



Per mille 

 32.21 

 31.55 

 32.47 



