The Gulf of Maine Temperature Structure Between 



Bar Harbor, Maine, and Yarmouth, Nova Scotia, 



June 1975-November 1976 



ROBERT J. PAWLOWSKI' 



ABSTRACT 



Monitoring of the temperature structure on a vertical section between Bar Harbor, Maine, and 

 Yarmouth. Nova Scotia, has permitted observation of the seasonal warming and cooling trends in the 

 northern Culf of Maine. Data have revealed a rise in both temperature and salinity from 197.5 to 197fi. 



INTRODUCTION 



METHODS 



In .liine \91Fi the Northeast Fisheries Center and the 

 Atlantic Environmental Oroup of the National Marine 

 Fisheries Service (NMFS) began a cooperative tempera- 

 ture study of the northern Gulf of Maine as a part of the 

 continuinj; NMFS Ship of Opportunity Program. Obser- 

 vations were obtained monthly through November 1976, 

 except for February 1976, aboard the Canadian National 

 Railways Ferry (C/N), MV Bluenose, during its service 

 from Bar Harbor, Maine, to Yarmouth, Nova Scotia. The 

 purpose of this paper is to review and summarize the 

 data, compare them with historical data, and compare 

 the data for the summer and autumn of 1975 and 1976. 



Long-term and seasonal temperature trends in the 

 Gulf of Maine have been noted by Bumpus and Chase 

 (1967) and Colton and Stoddard (1972). Colton (1968) 

 reported on a warming trend that reached its maximum 

 from 19.'i2 to ig.'i^, followed by uninterrupted cooling into 

 1967 Davis- found an end to this cooling trend in 1968 

 and resumption of a warming trend that continued into 

 197.5. Present monthly temperature observations show 

 that the warming trend has continued into 1976. The 

 monitoring of these trends is being continued. The area 

 between Bar Harbor, Maine, and Yarmouth, Nova 

 Scotia, was chosen because of the year-round ferry ser- 

 vice and our assumption that it gave a representative 

 section across the Gulf of Maine. Analysis of the circula- 

 tion in the Gulf of Maine (Bumpus and Lauzier 1965; 

 Lauzier 1967) showed that this section crossed both water 

 of Scotian Shelf origin off Nova Scotia and waters mixed 

 with the Bay of Fundy to the west. The temperature 

 structure of water deeper than 150 m represents localized 

 movement in the deep Gulf of Maine and the influence of 

 waters entering through the Northeast Channel. 



'Northeast Fisheries Center, National Marine Fisheries Service, 

 NOAA, Woods Hole. Mass.; present address: NOAA Ship George B. 

 Kelez {R-441), POB 176, Ryder Station, Brooklyn. NY 11234. 



■^C. W. Davis. 1976. Spring and autumn water temperatures in the 

 Gulf of Maine and Georges Bank. 1968-1975. ICNAF Res. Doc. No. 85. 

 Ser. No. 3897. 13 p. Unpubi. manuscr. 



F,.\pen(lahk' bathythermograph (\BT) stations were 

 taken at 30-min intervals along the ferry track (Fig. 1) on 

 dates specified in Table 1. Temperature data were col- 

 lected on a Sippican Model R-60.'3C XBT system, which 

 [)rovided continuous vertical temperature profiling with 

 ±0.2°C temperature and ±0.2' r depth accuracy. The 

 recorder was calibrated to specifications prior to each 

 cruise and checked for reference temperature (16.7°C) 

 before each cast. At the station, a sea surface bucket 

 temperature was taken and compared with the recorder 

 surface temperature. Comparison was also made 

 between the ship's bathymetric sounding and the trace 

 bottom mark. As data compared within the system's ac- 

 curacy, temperatures were read for 0.1°C. 



At each station, a sea surface salinity sample was col- 

 lected for processing ashore on a Beckman Model RS-7B 

 inductive salinometer. The salinometer was calibrated at 

 the beginning and end of each set of samples by water of 

 known conductivity. This method met the manufac- 

 turer's specified accuracy (±0.003%.), with data reported 



to o.orAo. 



Data are presented as vertical temperature sections, 

 sea surface and bottom temperature plots, and sea sur- 

 face salinity plots. Position data were used in organizing 

 these figures. Each position was determined at sea 

 through Decca radio navigation or radar ranges and bear- 

 ings on navigational aids or coastal land ma.sses. A stan- 

 dard bathymetric profile was also developed using ship's 

 soundings and the Canadian Hydrographic Office Chart 

 #401 1 . Temperature was contoured to vertical section for 



Table I. — Dates of expandable bathythermograph observations from 

 MV Bluenose between Bar Harbor, Maine, and Yarmouth, Nova 

 Scotia. 



18 .June 1975 



16 July 1975 



13 Aug. 1975 



17 Sept. 1975 



14 Oct. 1975 



18 Nov. 1975 



16 Dec. 1976 

 25 Mar. 1976 

 20 Apr. 1976 

 25 May 1976 

 16 .lune 1976 



15 July 1976 

 17 Aug. 1976 

 14 Sept. 1976 

 19 Oct. 1976 

 09 Nov. 1976 



