PHYSICAL OCEANOGRAPHY OF THE GULF OF MAINE 
691 
this connection by governing the Archimedian force that tends to pump the slope 
water westward to the Eastern Channel and so into the Gulf of Maine. This works 
most effectively in spring and early summer, but fluctuates so narrowly from season 
to season that only very narrow variations are to be expected in the temperature or 
salinity of any part of the gulf deeper than about 150 meters, from season to season 
or from year to year, or have actually been recorded there. 
This uniformity in the physical state of the bottom water on the floor of the 
deep trough of the gulf proves that the effects of the alternate seasonal warming 
and chilling of the surface do not penetrate deep enough to obscure the dominance 
of the slope water there; but the slight seasonal rise and fall of temperature that 
has been recorded at the bottom of the deep sink off Gloucester and between 
Jeffreys Ledge and the mainland (from which the slope water is barred by inclosing 
rims too shoal for it to overflow) is evidence that slight (but measureable) winter 
cooling and summer warming from above may be detected down to 200 meters, so 
far as the depth alone is concerned. 
It is because the slope water is warm, by comparison with the water with which 
it mixes within the gulf, that the bottom of the latter is usually warmest in the 
eastern side of the basin, at depths greater than 150 meters, where the inflowing cur- 
rent is chiefly localized (p. 921), coldest in the “sinks” in the inner parts of the gulf, 
from which the slope water is more or less effectually barred by submarine rims. 
The following differential table shows that the slope water has little effect on 
the deep temperature in such situations, as exemplified by the sink off Gloucester 
and by the trough between Jeffreys Ledge and the Isles of Shoals. This generaliza- 
tion applies also to the Bay of Fundy, from which most of the slope water is deflected 
by the topography of the bottom. In summer and autumn, it is true, the 175 to 
200 meter level may be as warm within the bay (6° to 7°) as without; but low salin- 
ity proves that this high bottom temperature chiefly reflects the active convectional 
currents of the bay by which solar heat received at the surface is dispersed more 
evenly downward there than it is anywhere else in the gulf in water equally deep. 
Depth, meters 
Cape Ann bowl, deepest level 
taken 
Basin outside, corresponding 
level i 
Date 
Station 
Temper- 
ature 
Date 
Station 
Temper- 
ature 
°C. 
°C. 
150 
Mar. 1, 1020 
20050 
1.68 
Feb. 23,1920 
20049 
6.66 
150—. 
Apr. 9, 1920 
20090 
( 2 ) 
Apr. 18,1920 
20115 
5. 38 
120 
20090 
2. 2.5 
do 
20115 
±3.80 
4. 69 
130— - 
May 4,1915 
102G6 
3. 55 
May 5, 1915 
10267 
110 - 
July 10, 1912 
Aug. 9, 1913 
10002 
4. 61 
July 15,1912 
10007 
±4.61 
128... 
180 
10087 
5. 17 
Aug. 9,1913 
10088 
10088 
3±5. 50 
6. 28 
140. 
Aug. 22, 1914 
10253 
4. 49 
Aug. 22,1913 
10254 
±5.30 
140 
Aug. 31, 1915 
10306 
5. 78 
Aug. 31, 1915 
10307 
±5. 10 
120 
Oct. 31, 1916 
10399 
5. 23 
Nov. 1, 1916 
10400 
±4.40 
150 
Dec. 29, 1920 
10489 
7.00 
Dec. 29,1920 
10490 
±6.00 
1 The table shows only the differential existing on the given dates between the deepest level, where a reading was taken 
within the bowl, and the corresponding level in the basin outside. It does not represent the seasonal cycle for the latter because 
of the difference in levels from station to station. 
> 150-meter reading not taken. 
8 130 meters. 
