PHYSICAL OCBANOGKAPHY OF THE GULF OF MAINE 



695 



from the deeper strata, by its opacity to this process (p. 694), that the water only a 

 meter or two down would lose heat much less rapidly than happens in reality, so 

 that the 20 to 30 meter level probably would not show enough cooling during the 

 winter months for the change in temperature to be measurable on our ordinary deep- 

 sea thermometers. 



Actually, however, vertical circulation is most active during the cold half of the 

 year; consequently, the mixing of the various strata of water is constantly bringing 

 up fresh water from below, to radiate its heat out into the atmosphere. The fact 

 that the upper 100 meters, or so, cools off so uniformly during the winter, instead of 

 only a thin surface film, is therefore wholly the result of convectional movements 

 of the water particles, induced either mechanically (by winds or tides) or dynami- 

 cally, if the surface water so chills that it becomes heavier than the underlying layer, 

 which, however, seems never to take place in the open gulf (p. 929). 



The rigorous climate of northern New England and of the Canadian Province 

 of New Brunswick so profoundly influences the sea temperature of the Gulf of 

 Maine that the following tables of the air temperatures at stations bordering the 

 gulf may be of interest.^* 



Normal air temperatures {Fahrenheit) 



Mean winter temperatures °F, with departures from normal {J. IF. Smith, 191S-1921) 



1911-12 



Boston... 

 Portland. 

 Eastport.. 



-1-0.08 

 -1- .02 

 -1.00 



'< From the XJ. S. Weather Bureau. 



