642 



BULLETIN OF THE BUREAU OF FISHERIES 



In 1916 the temperature of the upper 30 raeters was about the same a few 

 miles off Cape Ann on October 31 (station 10399, surface 10°, 30 meters 9.18°) as it 

 was on the 3d to the 16th m Passamaquoddy Bay, showing a regional difference of 

 about two weeks in the autumnal schedule between the southwestern and the north- 

 eastern parts of the gulf. This corresponds both to the land climate and to the 

 difference in latitude. 



Our only records of autumnal temperatures for the offshore parts of the gulf 

 later than the first week of September are for its western and southwestern parts, 

 where serial readings were taken on November 1, 1916 (station 10401), and again 

 on the 8th of the month (station 10404). In this very cold year the autumnal 

 warming of the deeper layers may have lagged some weeks behind the normal; the 

 inflow of water of high sahnity into the bottom of the trough seems also to have been 

 in smaller volume than usual. Consequently, the temperatures of 1916 can hardly 

 be taken as typical for depths greater than 100 meters. 



Surface readings about 0.5° higher in the ofSng of Cape Ann (station 10401, 

 10.6°) than near Gloucester, 0.9° warmer than off the Isles of Shoals, and 1.3° 

 warmer than off Penobscot Bay on November 1 and 2 of that year show cooling 

 most rapid next to the land, as might be expected. Tliis regional difference is 

 slight, however, and the deeper strata show much the same autumnal change off- 

 shore as they do closer to land, with the 40 to 70 meter level warming slightly (fig. 

 72) while the surface cools. At depths greater than this annual differences entirely 

 overshadowed any seasonal alteration that may take place in the western side of 

 the basin between August and October. 



As a result of the progressive equalization of temperature, horizontal as well as 

 vertical, that takes place during the autumn, the regional variation in the temper- 

 ature of the western side of the gulf was only about 1.5° to 2° at any given level 

 deeper than 15 meters in the first week of November, 1916. This close approach 

 to uniformity is probably typical of the season, though the precise temperature at 

 any level varies slightly from year to year. 



The average temperature of the region west of the longitude of Penobscot Bay 

 and north of Cape Cod is approximately as follows by the first of November in 



No records of the subsurface temperatures have been taken on Georges Bank 

 in autumn. In the shallow water of Nantucket Shoals autumnal cooling may at first 

 reduce the temperature of the sm-face slightly below that of the bottom, the Halcyon 

 having recorded surface readings of 11.6° to 12.2° on October 1, 1925, on the shoal, 

 when the bottom water was 12° to 13.5° in a depth of about 25 meters (p. 1013). 



