Portland Lightship (Figure 3, Table 3) 



Svirface temperatures from May through August, 1957 » were well 

 above the 1956 readings and above the mean for 19U7-1956, except for a 

 drop during the first 10 days of July. After Septeiaber, however, they 

 fell below both the mean and the 1956 values. 



Minimum temperatures of less than 38° occurred in March, and 

 were some two degrees warmer than the 19 5° minimum. The thermocline be- 

 gan to develop in raid-April and reached a maxim\m in early August with 

 surface tanperatures above 60"?, more than 2 degrees warmer than the 

 1956 maximum; bottom naxiinum was greater than 48° F in late August. By 

 raid-November the themocline had been destroyed, the water becoming iso- 

 thermal at Ii6° . Chilling continued nore rapidly during December than it 

 had the year before. 



Surface salinities were uniformly higher throughout the year 

 than the comparable 1956 values and showed less fluctuation. The mini- 

 mum in terms of 10 day means was 31.1i6 "/oo and occurred in late May; 

 the 1956 minimum was less than 29 °/oo in early May. Highest surface 

 salinities, just under 33 "/oo, appearea in February and again in Decem- 

 ber. 



Bottom salinities ranged from slightly above 33 °/oo in Feb- 

 ruary and again in the late fall to less than 3 Lit °/oo in July. There 

 was less difference between surface and bottom salinities in 1957 than 

 there had been the previous year. 



