PHYSICAL OCEANOGBAPHY OF THE GULF OF MAINE 



665 



Massachusetts Bay is warmest) , the 20-meter level early in September, 40-meter 

 level about the 1st of October, and the 70-meter and 100-meter levels during that 

 month or the next. 



3. NEAR MOUNT DESERT ISLAND 



Off Mount Desert, where tidal stirring keeps the water thoroughly mixed, surface 

 to bottom, throughout the year, the column cools nearly uniformly at all levels 

 during the autumn and warms only slightly more rapidly at the surface than in the 

 deeper strata during the spring (fig. 88) , so that the period when the surface is more 

 than 1.5° to 2° warmer than the 20 to 40 meter level averages 2 to 3 months instead 

 of 5 to 6 months, as in Massachusetts Bay; and the 40-meter level warms to its 



"- 5! Si ■>< 5; !^" 

 Nov. Oec. 



S> S S S S S "> 



^arr. feA 



A7tprc/2 Afir /7i:7y 



<0«3SNKr^NK 



JO » 10 « 



~/u/7e ^u/y 



Au^. Je/>t Oct A/ov £>ec. 



Fig. 87.— Composite diagram of tlie seasonal variations of temperature at Prince station 3, in the Bay of Fundy, between 

 Grand Manan and Petite Passage, from November, 1916, to November, 1917, from Mayor's (1923) data 



maximum for the year only a month or so later than the surface, instead of about 2 

 months later. The autumnal equalization of temperature also takes place by the 

 first week of October near Mount Desert, a month earlier than in the deep part of 

 the Bay of Fundy (fig. 87) but only a week or two earlier than in Massachusetts 

 Bay (fig. 86). 



4. WESTERN SIDE OF THE BASIN 



Probably the western arm of the basin (fig. 89) is less subject to tidal stirring in 

 its upper strata than any other part of the gulf. Therefore, it is not surprising to 

 find the seasonal rise and fall of temperature of its superficial stratum (surface to 40 

 meters) closely reproducing that of Massachusetts Bay, except that the temperature 



