Slope Water 

 Surface Layer 



In 1969 the pocket of warm water centered 

 around station 20 noted under tlie temperature 

 discussion was also characterized by salinity 

 values typical of Gulf Stream water (>36°/„o) 

 (fig. 54). Vertical gradients are apparent in the 

 surface layer waters in section 1 of the 1968 

 salinity profiles. However, to the west (sections 

 2 and 3) there was a shift to moderate horizontal 

 gradients. This feature is similarly exhibited in 

 the temperature and sigma-t profiles. 



Intermediate and Bottom Waters 



Both years were manifest of weak gradients. 

 Salinity values ranged from 35.3°/o„ at the 150 

 meter level to 34.9°/oo in the deeper waters in 

 1968 while 1969 values averaged 0.2°/oo higher. 



SIGMA-T 



Examination of profiles of sigma-t for both 

 cruises revealed one feature of particular interest. 

 Isopycnals for ICNAF 69-1 sigma-t se<"tion 4 

 (fig. 62) indicated a moderate current through 

 the Eastern Channel. Isopycnals with a slope 

 of one meter per nautical mile or greater were 

 observed in this vicinity. Salinity and tempera- 

 ture profiles for the same section (figs. 48 and 

 55) also suggested this same movement as the 

 isohalines and isotherms were nearly congruent 

 with the isopycnals. 



The comparatively warm (6°-7° C.) and 

 highly saline (>34°/„o) bottom water in the 

 Gulf of ]\raine basin alludes to an origin of Slope 

 Water or even, perhaps. Gulf Stream Water. 

 Dissolved oxygen content of the water in the 

 basin (4.3-5.4ml/l) (fig. 68) was typical of 

 Gulf Stream Water. 



The distribution of density along the edge of 

 the continental slope is probably the motive 

 power that brings water of these characteristics 

 into the Gulf of IMaine via the Eastern Channel. 

 A considerable body of evidence has been ac- 

 cumulated to the effect that the zone along which 

 coastal and oceanic waters mix and where Slope 

 Water is formed averages somewhat higher in 

 density than water on the continental slope. 

 Bigelow (1927) confirmed the findings of several 

 earlier surveys in this region. He concluded that 

 lower densities exist along the outer edge of the 

 offshore banks, abreast of the Gulf of Maine and 



off Xova Scotia, than along the continental slope 

 that bounds the banks on the offshoi-e sides. 



Examination of sigma-t profiles for stations 

 2-5 of section 1. and for stations 12-14 of section 

 2, reveals strikingly steep density gradients down 

 to 250 meters, with the higher values toward the 

 offshore side of the slope. Consequently, the 

 mass of water on the shelf above 250 meters had 

 a tendency to drift seaward (to the south). 



With dynamic forces tending to drive Slope 

 Water out to sea from the continental shelf 

 (southerly off Cape Sable and La Have Bank), 

 the Coriolis force would deflect this drift to the 

 right. In this manner a dominant drift from 

 east to west develops along the upper part of the 

 continental slope off La Have and Browns Banks. 



So long as the dynamic motion for this drift 

 jiersists, the entrance of the Eastern Channel is 

 supplied with the Slope Water from the east. 

 In this fashion, the current that flows into the 

 bottom of the Gulf of Elaine basin draws from 

 Slope Water formed at approximately equal 

 depths on the Xova Scotian slope. This is con- 

 firmed by the fact that temperatures and salini- 

 ties pro\ed to be very nearly the same in the 

 bottom of the Channel (7°-8° C. and 33.50%„- 

 34.75°/oo at 150-200 meters) as at equal depths 

 on the slope off La Have and Browns Banks 

 (6.5°-9° C. and 33.50°/oo-35.25%o). 



The Slope Water, moving westward is forced 

 against Browns Bank by the earth's rotation 

 (Coriolis force). Consequently with the Eastern 

 Channel offering an open route for this water to 

 the right, Bigelow (1927) has suggested that 

 ". . . it is reasonable to think of a screwing mo- 

 tion as taking place into the Eastern Channel . . ." 

 so long as the necessary density gradients exist 

 off the Scotian Slope. 



CIRCULATION 



A knowledge of the circulation patterns in the 

 Gulf of JNIaine should provide further insight 

 into the seasonal variance of isothermal and 

 isohaline conditions. 



Circulation patterns in this region have been 

 described by various authors. Bigelow (1927) 

 determined the circulation pattern in the Gulf 

 of Maine to be a general counterclockwise eddy 

 augmented by an inflow of water on the eastern 

 side from over the Nova Scotian banks. The 

 inflow causes a displacement of water south and 



