686 BULLETIN OP THE BUREAU OP PISHERIES 



source and by the Cape Sable "dead water" (p. 834) reaches the eastern side of the 

 gulf as a warming, not as a chilling, agency, actually 1° to 3° higher in temperature 

 than the water with which it mixes to the westward of Cape Sable. 



One more thermal aspect of the Nova Scotian current (this the most important 

 of all) demands brief examination — namely, its more general influence on the tem- 

 perature of the gulf as distinct from any regional differences which it may cause 

 within the latter. In other words, to what extent is the Nova Scotian current 

 responsible for the boreal character of the gulf? Would the latter be considerably 

 warmer without it? 



Until systematic exploration of the gulf was undertaken in 1912 it was gener- 

 ally assumed that the considerable contrast in temperature between the Gulf of 

 Maine, on the one hand, and the tropic water outside the edge of the continent abreast 

 of its mouth, on the other, resulted directly from the chilling effect of some such cold 

 stream from the north and east, though the Labrador and not the Nova Scotian cur- 

 rent was usually given this credit. There is no escape from the conclusion that 

 with water at least 3° lower in temperature than that of the gulf flooding into the 

 latter for several weeks every spring, the gulf must be somewhat cooler than it 

 would be if this source of cold should be dammed off. 



The older view, that some Arctic current or other controlled the temperature all 

 along the seaboard of the gulf, was largely based on the supposition that the latter 

 is a very cold body of water. It is a truism that the gulf, with a mean annual sur- 

 face temperature of about 8° to 9°, is considerably colder than the average for its 

 latitude over the oceans as a whole, which is given by Kjiimmel (1907) as about 

 14°; so, in fact, is the whole coastal belt along the North American seaboard from 

 Nova Scotia to Florida. However, "cold for its latitude" is by no means synony- 

 mous with "cold for its geographic position", and it is more because of its contrast 

 with the tropic waters of the so-called "Gulf Stream" than because of its absolute 

 temperature that the coolness of the Gulf of Maine has impressed students and 

 laity alike. In attempting to estimate whether the gulf is actually colder, and if so, 

 how much colder, than it would be if its offshore banks were to rise above water 

 and so dam it off from currents, warm or cold, the situation of the gulf to leeward 

 of the continent, and the air climate over the land mass from which the chilling 

 winds of winter blow out over the sea, are factors of primary importance. The 

 actual effect which winter chilling by cold air exerts on the temperature of the gulf 

 is discussed in some detail in a later section (p. 692) . For clarity, however, I must 

 repeat here that owing to the great difference in capacity for heat between air and 

 water the gulf is but little warmed by warm air blowing over it in summer (drawing 

 its vernal warming almost wholly from direct solar radiation) , but is very efl'ectively 

 chilled by the cold ak of winter. 



If the Nova Scotian current did cool the surface of the gulf generally to a tem- 

 perature more than a degree or two lower than would result from this winter chilling 

 alone we might expect the mean temperature of the upper 40 meters to prove consid- 

 erably lower in the eastern side of the gulf than in the western the year round; but 

 by actual observation the difference is no wdder in this respect between the parts of 

 the gulf most and least open to the cold current than might be expected to accom- 

 pany the difference in latitude between the stations in question. 



