Five Fathom Bank Lightship 



Surface temperatures at Five Fathom Bank Lightship were 

 somewhat lower, month by month, during the first half of the year than 

 the mean for 19li7-195$ (Bumpus, 19^7), were conparable during the autumn, 

 and significantly warmer at year end. The annual mean was a degree lower 

 than the 19U7-19^5 mean. 



Minimum temperatures of less than 39°F occurred surface to 

 bottom during the last third of January and first two-thirds of Feb- 

 ruary and again during the last third of %rch, A winter maximum of 

 Itl°F"^was observed during the second third of March. Ihe thermocline 

 began to develop in early April. Maximum temperatures of greater than 

 7l;°F at the surface were observed in mid-August. Maximum temperatures 

 at the bottom were not observed vmtil the fall overturn began during 

 the first third of October. "Hie year ended with the water about 7°F 

 warmer throughout the whole colujim than at the beginning. 



As at Winter Quarter and Chesapeake Lightships the summer 

 warminr* throu-^hout the water column appears interrupted from time to 

 time. This is most conspicuous during mid-July and late September. 



The salinity at the surface commenced between 32. 6°/°° ^^^ 

 33° /oo in January, gradually declined to 30.5°/oo in early Jime and re- 

 covered to 32.5°/oo at year end. Salinity at the bottom tended to fol- 

 low the salinity at the surface during the winter and spring months un- 

 til the thermocline began to develop, following which the bottom sa- 

 linity tended to keep lo/oo more saline than the surface. 



74 



