PHYSICAL OCEANOGRAPHY OF THE GULF OF MAINE 



941 



to state whether this creep involved the whole breadth at this depth or (which seems 

 more likely) hugged its Browns Bank slope, as in the shoaler strata. 



In interpreting the dynamic contours in terms of potential drift at a depth at 

 which the basin of the gulf is entirely inclosed except for one narrow channel, it is 

 obvious that prime consideration must be given to the contour of the bottom, as this 

 controls the possible movement of the water. When this is taken into account, the 

 March chart (fig. 190) affords the best clue yet available to the movement of the 

 slope water over the floor of the gulf at a season when this is entering in large volume 

 via the trough of the Eastern Channel (p . 850) . Dynamic contours for the 1 50-decibar 



Portland 



Fig. 190. 



-Dynamic gradient, bottom to 130 decibars, referred to the southeastern side of the gulf as base station, for 

 February and March, 1920. Contour lines for every dynamic centimeter 



level, like the distribution of temperature and of salinity, show this indraft following 

 the eastern side of the basin inward, to eddy westward and so southward; but instead 

 of completing a circuit around the cyclonic center ("low" on the chart — fig. 190), 

 the drift wiU obviously be deflected by the slope of Georges Bank. The angle at 

 which the contour (or stream) lines strike the latter suggests an overflow into the 

 dead western side of the basin. It is here, then, as well as along the northern 

 slopes of the gulf, that the consumption of this slope water chiefly takes place dur- 

 ing the early spring, as tides and 'wind currents constantly mix it with the less saline 

 but colder stratum above. 



