PHYSICAL, OCEANOGRAPHY OF THE GULP OF MAINE 681 



floods westward into the Gulf of Maine every spring, in some years into the summer. 

 It is obvious that if this reached the gulf close to zero in temperature, as it is farther 

 east, as well as in large volume, it would effectively cool the eastern side of the gulf 

 just as it cools the coastal zone along outer Nova Scotia, for it is considerably colder 

 than the central part of the gulf even at the season when the latter is at its coldest. 

 This difference in temperature widens during the spring as the vernal warming of the 

 gulf proceeds. Only once (March 29, 1919) have we found this icy Scotian water, 

 0° in temperature (p. 553) and low in salinity (p. 727) , flooding the surface as far west 

 in the gulf as the eastern side of the basin; and, as pointed out (p. 558), the duration 

 of this intrusion of zero water seems to have been brief, because the temperature of 

 this side of the gulf had risen to 2° to 4° by the 28th of April and to 4° to 6° by the 

 end of May (p. 560). 



I can not state whether the cold stream from Banquereau brings water as cold 

 as this to the Gulf of Maine every spring. In 1920 it certainly did not do so until 

 after mid April ^^ (if at all) , when the temperature was still no lower from German 

 Bank and Cape Sable out across the Northern Channel to Browns Bank in the 

 eastern side of the gulf than in the northern and western parts; in fact, slightly 

 higher than in Massachusetts Bay, though the latter is so much farther removed 

 from any possible effect of cold water from the east and north. In 1915 the band 

 of zero water had extended westward past Halifax by the end of May, probably as 

 far west as Shelburne. However, it is unlikely that the Gulf of Maine received any 

 water so cold during that spring; surface readings as high as 3° to 3.5° in the region 

 of German Bank on May 6 to 7 (stations 10270 and 10271) certainly do not suggest 

 this. So sudden a dislocation in temperature had developed by June of that year 

 between the eastern side of the gulf (5° to 8°, surface to bottom) and the coldest 

 band on the Shelburne profile* (0.7 to 0.9°, p. 582) that the latter no longer exerted any 

 cooling effect on the temperature to the westward of Cape Sable. 



This evidence suggests that while icy water from the Banquereau region (p. 832) 

 reaches the Gulf of Maine as cold as zero for a brief period during some springs, in 

 most years it is so warmed en route by mixture with water of higher temperatures 

 in the neighborhood of Cape Sable that it enters the eastern side of the gulf only a 

 degree or two colder than the water it meets there. 



The thermal effect which the Nova Scotian current exerts on the Gulf of Maine 

 is also limited by the fact that it passes Cape Sable as a surface and not a bottom 

 drift (p. 712), its deeper strata being deflected past the Northern Channel and into 

 the so-called "Scotian Eddy" by the obstruction offered to its westward movement 

 by the rising slope of Roseway Bank (p. 836) . With the advance of spring the surface 

 of the Nova Scotian current warms, by the sun's rays, as the source of low temper- 

 ature (ice melting to the eastward) is gradually exhausted, until by July the surface 

 attains a higher temperature all along Nova Scotia (12° to 13°)^^ than around Cape 

 Sable or in the eastern side of the Gulf of Maine, although the bottom water only 

 20 to 30 meters down continues icy cold. In consequence of this solar warming of 

 the superficial stratum the surface drift that persists from the eastward past Cape 



i8 On the 17th lo 19th of that March the coldest water (+0.3° to 0.5°) was then apparently flowing westward between La 

 Have and Eoseway Banks at the 20 to 40 meter level. 



»• For summer temperatures over the Scotian shelf see Bjerkan (1919) and Bigelow (1917). 



