PHYSICAL OCEANOGRAPHY OF THE GULF OF MAINE 
745 
The most instructive feature of the May chart in the eastern side of the gulf is 
the similar expansion of surface water less saline than 32 per mille westward over 
the basin from the offing of Cape Sable, which owes its low salinity to the Nova 
Scotian drift from the eastward. 
The critical isohaline (32 per mille) bounding this tongue had been carried about 
as far west into the gulf as this at least a week earlier in the spring of 1919, with 
actual values almost precisely the same. 88 Consequently, the picture presented on 
the surface chart for May (fig. 120) may be taken as typical of the season when the 
flow into the gulf past Cape Sable is at its maximum, irrespective of the precise 
date when this falls. 
The lack of data on the salinity of the southeastern part of the Gulf of Maine 
for May is a serious gap, for without such it is impossible to tell how far the fresh- 
ening effect of the Nova Scotian water extends toward Georges Bank, or over the 
latter, when it is at its maximum. However, it is certain that water of low salinity 
from this eastern source did not reach the southwestern part of the bank at any 
tune prior to the 17th of May in 1920, whatever may have happened later that spring, 
because no appreciable alteration took place in the salinity of the surface, which 
was about the same there on that date (station 20129) as it had been on February 
22 (station 20045). 
We also await observations on the salinity of the shoal water along the west 
coast of Nova Scotia for May, to show how low it is reduced there by vernal fresh- 
ening from local sources. It is not likely, however, that the eastern margin of the 
open Gulf of Maine ever falls below 30 per mille in salinity, unless right at the mouth 
of some stream, because no large rivers open along this part of the coast, because the 
outflow from the Bay of Fundy is directed westward (p. 916), and because there is 
no reason to suppose that the Nova Scotian current ever brings water less saline 
than about 30.8 to 31.5 per mille past Cape Sable. 89 
It is a question of moment in the natural economy of the gulf whether and to what 
extent the water of the Nova Scotian current turns northward after it has passed 
Cape Sable. This the reader will find discussed in another chapter (p. 680). I need 
remark here only that the surface salinities for May, 1915, and especially the course 
of the isohaline for 32 per mille (fig. 120), mark a westward drift toward the center 
of the gulf; but considerably lower salinities off the mouth of the Bay of Fundy in 
May, 1915, than in April, 1920, suggests some movement of water in that direction 
also, from the cape, as characteristic of this season. 
The vernal freshening of the coastal belt of the gulf by land water, and of the 
eastern side by the Nova Scotian current, are annual events, though differing from 
year to year in their time schedule as well as in the magnitude of the alterations 
they cause. A considerable divergence from year to year has been recorded in May 
in the west-central part of the gulf, which neither of these sources of low salinity 
appreciably affects up to that season. If the early May state of this part of the 
gulf in 1915 (fig. 120) be the regular seasonal sequence to the April state, as repre- 
sented by 1920 (fig. 101), a considerable salting of the superficial water layer is to be 
88 Surface salinity 31.98 per mille at Ice Patrol station 21; 31.71 per mille at Ice Patrol station 22 on German Bank. 
89 Neither the Ice Patrol nor the Canadian Fisheries Expedition have reported salinities lower than 30.8 per mille along the 
outer coast of Nova Scotia in April or May. 
