Spring 1976 



The spring I97fi warming trend (Fig. 5) began in sur- 

 face waters during March. Minimum temperatures at 50 

 to 150 m were reached in March, while waters deeper 

 than 150 m continued a cooling trend until April and 

 May. As the spring progressed, coastal waters warmed 

 from the shores outward, while a thermocline developed 

 in the central gulf area above 50 m. These two processes, 

 along with the relatively constant temperature in deep 

 water, constricted the winter-cooled water into a 

 minimum temperature layer between 50 and 100 m. This 

 layer was similar to that found in summer 1975 (Fig. 2), 

 but lacked the cellular structure noted previously. 



Summer 1976 



The data from summer 1976 (Fig. 6) showed tempera- 

 ture characteristics similar to those of the previous year, 

 but generally 2°C warmer. The thermocline developed 

 through the summer, with rapid surface warming (>2°C) 

 in .lune and July, followed by a decrease in the warming 

 rate during August as waters neared maximum tem- 

 perature. The minimum temperature layer dissipated by 

 July, with continued warming at middepths through 

 August. Temperatures below 1.50 m warmed into June, 

 followed by a rapid increase in the eastern basin during 



July and continued increases in both basins through 

 August. 



Autumn 1976 



Autumn 1976 (Fig. 7) was characterized by a continu- 

 ation of stable water cohimn conditions and warming 

 into September, with yearly maximum temperatures be- 

 ing 1° to :\°C higher than in 1975. A change to cooling 

 and loss of stability occurred in October with a break- 

 down of the thermocline. This cooling continued into 

 November bringing temperatures and structure similar 

 to the previous year. Waters deeper than 100 m showed a 

 westerly shift of the 9°("^ isotherm, but otherwise main- 

 tained constant temperatures in September. October fol- 

 lowed with cooling and development of an 8°C cell in the 

 western basin. This cell dissipated with an unexplained 

 return to warming in November. 



The historical mean data (Figs. 8-13) show the same 

 major features found in the 1975 and 1976 data: the 

 development of a surface water thermocline, the spring- 

 summer minimum temperature layer, and a bottom tem- 

 perature inversion. Seasonal trends were consistent 

 between historical and present sections. Variations ex- 

 isted in the extent of thermocline development into 

 coastal waters and the change in deep bottom tempera- 

 ture structure. Temperatures were 1° to 5°C warmer in 

 1975 and 1976 than the mean historical temperatures. 



BAR HARBOR 



YARMOUT>< 

 10 n 12 



MARCH 76 

 BAR HARBOR 



Figures. — Vertical temperture sections {°C) for the Gulf 

 of Maine between Bar Harbor. Maine, and Yarmouth. 

 Nova Scotia, spring 1976. 



