This is consistent with Colton (1968) in which no 

 seasonal trends were noted for bottom temperatures in 

 the Gulf of Maine. Colton pointed out: 



It would appear that trends in subsurface temperatures can 

 be traced to variation in the composition of these offshore 

 waters as well as to the volume of their indraft through the 

 Northeast Channel. 



A review of the sections showed abrupt warming in Oc- 

 tober and December 197.5, and in July and August 1976. 

 These changes are presumably due to influence from 

 mixed slope water. The bottom circulation for the Gulf of 

 Maine inferred from seabed drifters indicates (Lauzier 

 1967) inflow to this area. However, due to lack of subsur- 

 face salinity data, the amount of slope water present can- 

 not be determined. Davis (see footnote 2) noted a bot- 

 tom-water warming trend from 1971 through 1974, with 

 abrupt cooling by autumn 1975 in the Gulf of Maine. The 

 slow rise in deep temperatures for these sections (Fig. 13) 

 and the differences between 1975 and 1976 for summer 

 and fall temperatures (Figs. 2, 3, 7, 8) indicate fall 1975 

 as a break in the existing warming trend, followed by a 

 return to warming in 1976. 



SUMMARY 



All sections showed similar water column structure 

 and seasonal changes when compared to historical sec- 

 tions, but temperatures were generally 1° to 5°C warmer 

 in the 1975-76 sections. 



Warming trends began in late winter and continued 

 through summer, progressing from the coast outward in 

 waters inshore of the 100-m isobath. Central gulf waters 

 developed a spring and summer thermocline above 50 m 

 that restricted rapid warming (>2°C/month) to surface 

 waters. Maximum temperatures occurred from late 

 August to September. Cooling trends began in Septem- 

 ber and October, developed homogeneous conditions by 

 late fall, and cooled through January. Reversal to a 

 warming trend occurred during February to March. 



A minimum temperature layer developed in the spring 

 months at middepths with constriction of winter-cooled 

 water by the surface thermocline and offshore progres- 

 sion of warmer coastal waters. This layer continued 

 warming with influence from surrounding layers and dis- 



sipated by late summer. The minimum temperature 

 layer appeared in 1975 to consist of two cold spells 

 separated by warmer water. Such structure may be 

 related to deep flow into and out of the northern Gulf of 

 Maine. Waters deeper than 150 m fluctuated in tem- 

 perature regardless of season, probably due to influence 

 from sporadic slope water inflow at the Northeast Chan- 

 nel. 



Oceanogra|)hic conditions in the Gulf of .Maine were 

 warmer in 1976 than in 1975. Fall 1976 followed with 

 cooling that brought similar temperatures for both years 

 by November. Surface waters in summer and fall 1976 

 were more saline (1%.) than in 1975. 



ACKNOWLEDGMENTS 



I thank the members of the .Atlantic Environmental 

 Group for the preparation of historical sections and for 

 assistance in gathering the data. A special word of thanks 

 is also in order to the officers and crew of the Canadian 

 National Ferry, MV Rluennse. for their outstanding as- 

 sistance throughout this project. 



LITERATURE CITED 



RUMPUS. D. F.. and -J. CHASE. 



196.'i. Changes in hydrography observed along the east coast of the 

 United States. ICNAF Spec. Publ. 6:847-8.'i:i. 

 BUMPUS. D. ¥.. and L. M. LAUZIER. 



196."). Surface circulation on the continental shelf off eastern North 

 America between Newfoundland and Florida. Ser. Atlas Mar. 

 F.nviron.. Folio 7. Am. Geogr. Soc. 14 ol. 

 CHAMBERLIN, J. L., J. J. KOSMARK, and S. K. COOK. 



1978. Initiation of monthly temperature transects acro.ss the north- 

 ern C.ulf of Maine, [n .J. R. Goulet and E. D. Haynes (editors), 

 Ocean variability: Effects on U.S. Marine Fishery Resources, p. 

 ■>h-i-->m. NOAA Tech. Rep. NMFS Circ. 

 COLTON. .1. B.. .Jr. 



1968. Recent trends in subsurface temperatures in the Gulf of 

 Maine and contiguous waters. .J. Fish. Res. Board Can. 25:2427- 

 24:!7. 

 COLTON. J. B.. .Jr., and R. .STODDARD. 



1972. .Average monthly sea water temperatures. Nova Scotia to 



Long Island, 1940.19.'S9. Ser. Atlas Mar. Environ.. Folio 22, Am. 



Geogr. Soc, [2 p]. 



197:i Bottom water temperatures on the continental shelf. Nova 



Scotia to New Jersey. NOAA Tech. Rep. NMFS Circ. 376, 55 p. 



LAUZIER. L. M, 



1967. Bottom residual drift on the continental shelf area of the 

 Canadian Atlantic coast. J. Fish. Res. Board Can. 24:1845-1859. 



10 



I Q npn iq7fl_fiq7ynriQ-S9 



