PHYSICAL OCEANOGEAPHY OF THE GULF OF MAINE 



541 



eastern slope of the gulf (against the right-hand side for an entrant current) to with- 

 in 90 meters of the surface in the manner with which cruises at other times of year 

 have made us familiar (p. 619). Temperatures are slightly lower in the shore ends of 

 this profile, as is usual for the cold season. Failure to obtain readings lower than 1° 

 may be explained on the assumption that solar warming is propagated downward to 

 a greater depth off Maine and off Nova Scotia by the strong tides of those localities 

 during the first three weeks of March, than in the western side of the gulf, where 

 tidal stirrmg is less active. 



The relationship existiog in March between the cold waters over Georges and 

 Browns Banks and in the Northern Channel, on the one hand, and the warm indraft 

 into the Eastern Channel, on the other, is illustrated by a profile following the arc 

 of the banks (fig 19). Bottom water of 6° to 7° in the Eastern Channel, banked 



Fig. 19.— Temperature profile running (rom the eastern part of Georges Banl^, across the Eastern Channel, Brown's Banlr, 



and the Northern Channel, March 11 to 23, 1920 



up like a ridge along its trough (isotherms for 3° to 6°), contrasts with 3° to 4.5° at 

 equal depths in the Northern Channel, where temperatures higher than 4° were con- 

 fined to a thin bottom layer deeper than 110 meters (station 20048). A bottom 

 temperature fractionally higher than 3° on Browns Bank points to some tendency 

 for the warm water that drifts in through the Eastern Channel to overflow the east- 

 ern rim of the latter; but the March data show that this circulatory movement was 

 limited to depths greater than 70 meters. Probably the fact that the readings on 

 Georges Bank showed no sign of any encroachment of the warm water in that direc- 

 tion, which is corroborated by salinity (p. 719), is due to the deflective effect of the 

 earth's rotation, deflecting the current to the right (p. 849) . Other features of the 

 profile that claim attention are the uniformity of temperature over the eastern part 

 of Georges Bank from east to west; the fact that the surface was fractionally warmer 

 than the 20-meter level there and over the Eastern Channel (a first sign of vernal 

 37755—27 3 



