CLIMATE AND THE DISTRIBUTION OF MARINE ANIMALS 



311 



torn, on May 3-5, 1953, than on April 16, 1920 

 (table 9). But the difl'erence between the two 

 sets of observations is seemingly no wider than can 

 be credited to the warming to be expected to take 

 place over the Bank, in any given spring, during 

 the 3-week interval between the dates when the 

 observations were made in the 2 3'ears. The dif- 

 ference, also, between slightly higher readings in 

 the deep channel north of Georges Bank (area M, 

 fig. 12) on March 23, 1953, than on the 20th of that 

 month in 1920 (table 9), is no greater than is to be 

 expected there from one spring to another during 

 any run of years, depending on the relative sever- 

 ity of the preceding winter, and on the seasonal 

 schedule and temperature of the Nova Scotian 

 drift from the east. But bottom temperatures 

 reported from Browns Bank in 1952, of about 41° 

 to 43° F. between February 15 and March 18 and 

 of about 39° to 46° between April 29 and May 11 

 (McLellan 1954, p. 408, figs. 2 and 3), contrasted 

 with bottom readings there in 1920 of 38.1° on 

 March 13 and of 37.8° on April 16, point to slightly 

 warmer bottom water on Browns Bank in early 

 spring in 1952 than in 1920. The surface, how- 

 ever, was about as cool in late March of 1953 as 

 in 1920 over the east-central part of the basin, 

 and about 1° colder than in 1920 over the south- 

 eastern slope of Georges Bank. 



The existence of an area occupied by water as 

 cold as 36° to 40° F., as outlined in the surface- 

 temperature charts for the eastern part of the 

 Gulf of Maine (fig. 14), shows that the responsible 

 factor was the cold Nova Scotian drift, which had 

 spread westward past Cape Sable before the last 

 week of March in 1953 but did not do so until April 

 in 1920, or, seemingly, in 1915 (Bigelow 1927: 

 p. 554, fig. 25; p. 578). In the seasonal schedule 

 of the drift, 1953 paralleled 1919, when a U. S. 

 Coast Guard cutter on ice patrol reported a 

 surface water temperature of 32° (but 38.7° to 41° 

 in the underlying water) on MaiTJi 29, 1919, in the 

 east-central part of the basin of the Gulf (Bigelow 

 1927, p. 553) where the temperature was 38° to 40° 

 at about the same date (March 23) in 1953. 



The contrast in this connection between 1953 

 (a warm spring in the sea), on tlie one hand, 

 and 1919 (a cold spring) and 1920 (a cold and 

 tardy spring), on the other, is good evidence that 

 the date on which the cold Nova Scotian drift 

 affects the temperature of the surface beyond 

 Cape Sable and the extent to which it does so are 



not correlated with the minimum to which water 

 has chilled during the preceding winter in the Gulf 

 of Maine, or with the relative forwardness of vernal 

 warming there, but that they are governed by 

 events along the Nova Scotian shelf to the east- 

 ward and within the Gulf of St. Lawrence. 



In 1953, surface water slightly colder than 40° 

 still occupied the area off Cape Sable (fig. 15) as 

 late as the first week in May. The westward 

 drift must have ceased soon thereafter, however, if 

 it had not done so already, for tiie temperature of 

 the surface water on Browns Bank had risen to 

 46.5°-48.5° by the last of May. It appears, 

 thus, that any tempering effect mild air tempera- 

 tures over tlie land mass in winter may have on 

 water temperatures off southern Nova Scotia 

 early in the following spring is counteracted more 

 or less completel3' by the chilling effect of the drift 

 from the east. 



August-September 



It is clear, from the evidence we have presented, 

 that the waters of the Gulf from the surface down 

 to 150 meters entered the season of vernal warming 

 between 1° to 2° and 4° to 4.5° warmer in 1953 

 than in the period 1913-25, though perhaps no 

 warmer than in the warmest of the years included 

 within that period. The data also show that the 

 temperatures of the Gulf continued about that 

 much warmer during the summer of 1953, though 

 with certain regional exceptions. In Boston 

 Harbor, the mean temperature of the warmest 

 month of 1953 (August, 67.2° F.) was about 2.6° 

 higher than the corresponding mean (64.6°) for 

 the 5-year period 1922-26. Similarly, Frank J. 

 Mather III reported surface readings of 70.5° to 

 71.5° in the eastern side of Cape Cod Bay, with 

 70° in the central part, as early in 1953 as July 19. 

 This contrasts with 64.6° recorded by the Halcyon 

 for tlie center of tlie Bay on August 24, 1922, 

 when the surface there was no doubt near its 

 warmest for the year. In 1953, as late as the 

 first week of September, the surface was still as 

 warm as 68° to 70° over the southwestern part 

 of the open basin of the Gulf, where 62.8° had 

 been reported on August 4, 1913, 67.2° to 68.0° 

 August 2.3-24, 1914, and 66.9° on August 12. 1926. 

 Similarly the surface readings in tiie general oflling 

 of Cape Ann (area A, fig. 16) averaged about 2.7° 

 liigher at stations in August 1953 than at 15 

 stations in that same montii in 1912, 1913, 1914, 



