522 BULLETIN OF THE BUEEAXJ OF FISHERIES 



TEMPERATURE 

 FEBRUARY AND MARCH 



It is most convenient to begin the account of the temperature of the Gulf of 

 Maine with the late winter and early spring, when the water has cooled to its 

 minimum for the year and before vernal warming has proceeded to an appreciable 

 degree. 



No definite date can be set for this state because of regional and annual varia- 

 tions, but experience in 1913, 1920, and 1921 suggests that the lowest temperatures 

 are to be expected over the gulf as a whole during the last week of February and 

 first few days of March, except from Cape Sable out to the neighboring part of the 

 basin, where the surface is coldest some weeks later, when the Nova Scotian current 

 is flowing from the east nast Cape Sable in greatest volume (p. 832). The tempera- 

 tures recorded during the February-March cruise of 1920 may not have been the 

 absolute minimum for that year, but the preceding winter had been so cold, with 

 snowfall so heavy, that probably the open gulf is never more than fractionally colder 

 than we then found it. The coastal belt may then be expected to chill below 2° at 

 the surface all around the gulf by the end of winter (fig. 1), its central and offshore 

 parts continuing slightly warmer (about 2.5° to 3.5°). In 1920 a surface tongue 

 equally cold had also developed off southern Nova Scotia by the middle of March, 

 spreading westward across Browns Bank but separated from the coast by slightly 

 warmer (2.2° surface) water close to Shelburne. Present knowledge of the seasonal 

 fluctuations of the Nova Scotian current (p. 832) also make it likely that some such 

 development is to be expected yearly. 



SURFACE 



The surface temperature falls fractionally below 0° in Cape Cod Bay during 

 winters when ice forms there in any amount. Thus in 1925, for example, the whole 

 column of water in its central and eastern sides, in 12 to 34 meters depth, chilled 

 to -0.4° to -0.7° by February 6 to 7, warming again to 1° to 2° by February 24. 

 Passamaquoddy Bay chills to nearly as low a figure (0.77° at 20 meters, February 

 23,1917; Willey, 1921). 



If the mnter of 1924-25 can be taken as typical (as seems fair, because rather a 

 greater amount of ice formed in Cape Cod Bay than usual, although the air tem- 

 peratures averaged warmer than normal and the snowfall less), a line from the tip 

 of Cape Cod to Boston Harbor will bound this 0° water in the Massachusetts Bay 

 region. Equally low temperatures no doubt prevail on the surface in the inner parts 

 of the bays and among the islands along the coast of Maine in winters when much 

 ice forms there. 



By contrast it is not likely that the surface of the basin of the gulf, including 

 the western part of the Bay of Fundy, ever cools below 2° at any season except for 

 a brief period later in the spring (p. 681), when the surface in the eastern side may be 

 chUled to 0° by the icy Nova Scotian current flowing past Cape Sable from the east. 

 Minimum readings of 3° to 4° are to be expected over the southern side of the basin 

 and on the eastern part of Georges Bank; 4° to 5° over its western half and off its 

 southwestern slope. 



