PHYSICAL OCEANOGBAPHY OF THE GULF OF MAINE 613 



Notwithstanding the paucity of August data for the open gulf proper south of 

 the Cape Cod-Cape Sable line (p. 594), it is possible to estimate the 100-meter tem- 

 perature of the southeastern part of the basin, of the Northern and Eastern chan- 

 nels, and along the oceanic slope of Georges Bank from the July stations for 1914, 

 because the general cycle of temperature makes it practically certain that these 

 localities would have been found sHghtly warmer in August. On this assumption, 

 the 100-meter level is about 3° colder in the Northern ChanneP^ than in the neigh- 

 boring part of the basin of the gulf to the west, with still lower temperatures (2° 

 to 5°) over the inner half of the continental shelf along the outer coast of Nova 

 Scotia (Bigelow, 1917, p. 182, fig. 16). The rather abrupt east-west transition 

 in temperature at the western end of this channel (fig. 56) also is evidence that no 

 general movement was taking place in either direction along its trough at the time. 



In the Eastern Channel, however, the 100-meter water (8° to 9°) is about as 

 warm as it is in the eastern side of the gulf, with a gradual transition to still higher 

 readings (11°) along the continental edge and to 14° and higher a few miles farther 

 offshore. However, the precise distance it is necessary to run out from the edge of 

 the continent to find water as warm as this at the 100-meter level, on any given 

 date, depends on the cu-culatory interaction between the cool banks water and the 

 much warmer and Salter oceanic water of the Atlantic Basin. Probably, how- 

 ever, the isotherm for 14° is always closer to the edge of the banks to the west of 

 longitude 68° than to the east of that meridian. 



The low temperature (8.98°) on the southeastern face of Georges Bank at 90 

 meters (station 10222) deserves attention because it suggests a drift of cool water 

 out of the gulf around the peak of the bank, salinity being too low there (34.18 per 

 mille) to allow of upwelling up the continental slope from the mid depths offshore as a 

 possible cause. This is corroborated by the density there, as explained below (p. 958) . 



The 100-meter level remains much more nearly constant in temperature through- 

 out the summer than do the overlying waters, with readings only about 1° higher 

 in the western side of the gulf at the first of September, 1915, than they had been 

 during the last week of the preceding June. 



In the eastern side of the gulf, where solar heat is more rapidly dispersed down- 

 ward by more active vertical circulation, the 100-meter level may be expected to warm 

 by 2° to 3° from June to the end of August; most rapidly along the eastern slope 

 of the basin and in the Bay of Fundy, where Mavor (1923) records an increase in 

 the 100-meter temperature from 3.92° on June 15 to 6.13° on September 7, 1919.'^ 



TEMPERATURE AT 150 METERS AND DEEPER 



Annual variations in temperature have proved wider than the regional dift'erences 

 at depths greater than 100 to 150 meters; nor has the regional distribution at differ- 

 ent levels been parallel from summer to summer. The following table shows the 

 western, central, and northeastern deeps of the basin fractionally warmer than its 

 eastern side in August, 1913. 



"The 100-meter temperature was 6.96° on July 25, 1916, at station 10229. 

 " At Prince station 3, about 10 miles southeastward from the western end of Orand Manan. 

 37755—27 8 



