PHYSICAL OCEANOGRAPHY OP THE GULP OP MAINE 919 



of the Gulf of Maine eddies. This same distribution of temperature, however, 

 reappearing in April, is reminiscent of a past state of circulation, not of a present 

 one, because the corresponding charts of salinity show the dominant set to have 

 assumed a southwesterly course, more nearly parallel to the coast line, from the one 

 month to the next (p. 743). Neither of these early spring charts of temperature 

 suggest any drift of warmer water into the eastern side of the gulf from offshore; 

 but some drift of this sort is indicated on the 40-meter chart for March (p. 525) by a 

 band warmer than 3° entering via the Eastern Channel. This indraft appears 

 more clearly at deeper levels (p. 526). 



With the advance of spring the regional inequalities of temperature become 

 increasingly significant, from the standpoint of circulation, as they outline the lines of 

 dispersal followed in the gulf by the cold water of the Nova Scotian current. In 

 general, temperature corroborates salinity to the effect that the current did not begin 

 to flood westward past Cape Sable until after the middle of April in the year 1920, 

 though it had exerted its chilling effect in this direction as far as the eastern side of 

 the basin of the gulf by the last of March the year before (p. 553). The isotherms 

 for May (fig. 27), however, suggest more of a tendency for this Nova Scotian water 

 to spread northward toward Maine and the Bay of Fundy, as well as westward in 

 the gulf, when at its head, than do the isohalines (p. 745). 



Rising temperature, like rising salinity, reflected a slackening in the current in 

 1915 from May to the last half of June, when an abrupt transition in the temperature 

 of the coldest stratum, from the Eastern Channel (about 8.1°) to the vicinity of 

 Cape Sable (about 0.7°), located its southwestern boundary at Browns Bank. This 

 is also indicated by the abrupt transition from colder to warmer water along the 

 western slope of the bank at 40 meters; but the low temperatures recorded over the 

 southwest slope of Georges Bank on the July profile for 1914 (fig. 58, p. 616)*° is 

 readiest explained as reminiscent of a cool current skirting the bank from northeast 

 to south some time previous. It seems that in the cold year 1916 such a drift of 

 cool water was either in much greater volume or persisted until later in the season, 

 for it is difficult to account otherwise for the band of low temperature which the 

 Grampus encountered over the southwestern slope of the bank that July (p. 629). 



. "The facts that the cold band of 1916 lay almost exactly in the prolongation 

 of that of 1914; that a similar streak of comparatively low temperature (6.4°) was 

 encountered at the same relative position on the shelf some 60 miles farther west in 

 1913 (station 10062) ; and that the axis of the coldest water noted on the shelf south 

 of Nantucket in 1889 (Libbey, 1891) merely prolongs this general zone, practically 

 amount to proof that a northeast to southwest flow of cold water takes place there 

 annually in late spring or summer, dovetailing in between the warmer and fresher 

 bank water on the north and the Gulf Stream on the south." (Bigelow, 1922, p. 166.) 

 Its source is discussed elsewhere (p. 848). The July isotherms for 1914 locate its 

 extreme western boundary between longitude 68° and 69°, where the 40-meter chart 



>' This also appears on the corresponding chart for the 40-meter lerel, but is complicateti there by active vertical mixing that 

 maintains a higher temperature over the shoal parts of the bank at this depth (lower at the surface) than on its southern side; 

 the alternation of a warm with a cold belt along the bank, outlined in the 40-meter chart (fig. 53), is therefore partly of local 

 origin. 



