PHYSICAL OCEANOGEAPHY OF THE GULF OF MAINE 



545 



Meteif 



10 



Temperature, Centigrade 



r 2° 3° 4° 



The winter of 1913 (Bigelow, 1914a, p. 391) was 

 intermediate between 1920 and 1921 in temperature 

 at this locality, with readings of 2.83° on the surface 

 and 3.11° on bottom in 82 meters at a near-by loca- 

 tion on February 13 (station 10053), when the mini- 

 mum temperature for the winter was recorded. 



An equally interesting annual difference is that 

 the temperatures of late February and early March 

 were lowest at the surface in 1913 and 1921, whereas 

 in 1920 vernal warming already had raised the tem- 

 perature of the surface fractionally above that of the 

 underlying water by March 4. On February 24 to 

 28, 1925, the bottom was fractionally the warmest 

 level at one deep station {Fish Hawk station 18a), 

 while the surface was warmest at another (station 2) , 

 with the mid-stratum fractionally the coldest at 

 both. Thus, the date at which the vernal warming 

 of the surface begins to be appreciable does not 

 necessarily mirror the state of the preceding winter, 

 whether a cold one or a warm one in this part of the 

 gulf (1920 was a very cold winter), but depends 

 more on the degree of cloudiness, the precise condi- 

 tion of air, the direction of the wind, the tempera- 

 ture of the air, and on the snowfall from the middle 

 of February on. 



Turning now to the coastal belt just north of 

 Cape Ann we find very little difference in actual tem- 

 perature between readings of 2.4° to 3.7° at the Fish 

 Hawk stations (Nos. 20 to 28) for March 10, 1925, 

 and Welsh's records of 3.8° to 3.9° on March 19, 

 1913; but with the surface about 1° warmer than 

 the 30-meter level at all these Fish Hawk stations, 

 but the whole column virtually uniform in tempera- 

 ture down to 120 meters in 1913, it is evident that 

 the vernal warming of the surface commenced at 

 least two weeks earlier there in 1925 than in 1913. 

 The year 1920 was certainly colder at this general 

 locality than either 1913 or 1925, because the surface had warmed only to 3.05° 

 there by the 6th of April (station 20092). 



20 



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130 



140 



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160 



Fig. 21. — Vertical distribution of temperature 

 off Gloucester during the first week of 

 March of the years 1913, 1920, and 1921, to 

 show the annual variation. A, March 1, 

 1920 (station 20060); B, March 5, 1921 (sta- 

 tion 10511); 0, March 4, 1913 (station 10054) 



