690 BULLETIN OF THE BUREAU OF FISHERIES 



The evidence just outlined leads to the conclusion that the Nova Scotian water 

 flowing into the Gulf of Maine from the eastward in spring does not lower the gen- 

 eral temperature of even the coldest localities and levels in the gulf more than a 

 degree or two below the values that would prevail were the gulf as nearly inclosed 

 as are the Black Sea or the Norwegian fjords. Nevertheless, the Nova Scotian 

 current does act as a decidedly effective cooling agent, for without the cold 

 water from this source the comparatively high temperature of the slope water, of 

 the surface inflows from the region off Browns Bank, and of occasional overflows of 

 tropic water (p. 836), would hold the gulf several degrees warmer than it actually is. 

 These warm sources the Nova Scotian current counteracts, and in counteracting 

 them it has its chief thermal importance in the Gulf of Maine. 



THERMAL EFFECT OF THE SLOPE WATER 



Were the gulf an inclosed basin, with little or no inflow over its floor, we should 

 expect to find its bottom temperature certainly no higher then 5° to 6° and proba- 

 bly as cold as the mean annual temperature actually is in the deep sinks in the 

 western side of the gulf, namely 4° to 5° (p. 688). In reality, however, we have only 

 once found the bottom water in the basin of the gulf colder than 4° in depths of 

 175 meters, or deeper, at any locality, season, or year.'' Only 4 out of 64 deep 

 stations in the basin have given bottom readings lower than 4.5°. On the other 

 hand, 26 have been warmer than 6° on bottom; and the bottom temperature for all 

 as deep as 175 meters has averaged about 6°, or lJ/^° warmer than the mean annual 

 temperature at the 100-meter level around the shores of the gulf and 2° warmer 

 than the mean bottom temperature in the trough of the Bay of Fundy. The high 

 salinity, coupled with the precise temperature of this bottom water, identifies it 

 beyond dispute as slope water flowing in along the trough of the Eastern Channel 

 (see discussion p. 842) . The slope water, then, brings warmth to the deeps of the 

 gulf suflacient to raise the bottom temperature of the basin a degree or two higher 

 than would be the case if no such current flowed in; consequently it must be named 

 a warm current as it affects the gulf, not a cold one. 



The physical characteristics of the slope water, as it drifts inward along the 

 bottom of the Eastern Channel, have proved so uniform from season to season and 

 from year to year (temperature about 6° to 7° and saHnity about 34.6° to 35° per mille 

 in spring and summer) that the causes for the variations recorded in the temperature 

 and salinity of the deepest water within the gulf are to be sought in fluctuations in 

 the volume and velocity of the inflowing bottom drift rather than in vai'iations in 

 the temperature or salinity of the latter. Such fluctuations, in turn, almost certainly 

 have a two-fold cause. In part they result from corresponding variations in the 

 amount of slope water being manufactured along the continental slope to the east- 

 ward shortly prior to the date of observation, and in the proportional amounts of 

 the various waters, cold and warm, that enter into its composition. The seasonal or 

 or other secular differences in the density gradient over the continental slope from 

 Browns Bank to La Have Bank, however, probably play a more important role in 



"Bottom temperature 3.54° at ISO meters at station 10283 ofl the Bay of Fundy, June 10, 1915. 



