PHYSICAL OCEANOGRAPHY 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 slightly warmer in August. On this assumption, 
the 100-meter level is about 3° colder in the Northern Channel 32 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 circulatory 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. 33 
TEMPERATURE AT 150 METERS AND DEEPER 
Annual variations in temperature have proved wider than the regional differences 
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. 
32 The 100-meter temperature was 5.96° on July 25, 1915, at station 10229. 
33 At Prince station 3, about 10 miles southeastward from the western end of Grand Manan. 
8951—28 40 
