Portland Lightship 



Surface temperatijres for 1956 were, on the whole, warmer than 

 the means for the period 1925-19U1, but cooler than the means for 19U7-195i6. 

 (Bmous, 1957). 



Mniinum temperatures occiirred during the latter two-thirds of 

 January with temperatures of slightly less than 37°F and during the last 

 third of March at less than 36°?. By mid-April, a thermocline had begun 

 to develop which reached a maxima in mid-August m.th surface temperatures 

 in the high 50's and bottom temperatures in the low UO's. During the first 

 third of September, the bottom temperatures suddenly increased 7 or 8 F and 

 remained high, ca. U8°F, until mid-November when temperatures at the sur- 

 face had dropped to such a level that complete turnover was taking place 

 in the water column. Ihroughout the remainder of the year, temperatures 

 between the surface and bottom were within a degree of each other, the sur- 

 face being slightly cooler. 



The year commenced with surface and bottom salinity at approxi- 

 mately 33°/00. The salinity gradually declined toward the end of March to 

 ca. 320/00. Beginning in April, the surface salinity lowered abruptly, 

 reaching a minimum of 290/OO dtiring the first third of May. Sijrface sali- 

 nity tended to remain less than 31°/00 until August, followed by a gradual 

 increase to 32.5°/00 at year end. 



Bottom salinities tended to remain at about 32°/00 between April 

 and August but descended to less than 31°/00 during the first third of May 

 and again during the last half of July whereupon bottom salinities remained 

 slightly higher than surface sal5.nities until the last third of December. 



11 



