Paper 19 



197A/' and 2C warmer than in 1975. The extent and timing of this 

 cooLinc may be controlled by movement of the Slope Front. 

 However^ the fact that the deepenino of the isotherms on the 

 outer shelf had occurred in Aoril during each of the three years/ 

 suggested the alternative explanation that the minimum Shelf 

 Water temperatures of early spring promoted cross-frontal mixing 

 with the warm Slope Water. Salinity data will te necessary to 

 determine which explanation is correct. 



Shoreward of the 50-m isobath/ the bottom water began to warm by 

 mid-March/ rising to about 7C (warmer inshore) before thermal 

 stratification set in by early May/ and established this water as 

 an isolated cold core. Although data were were not obtained 

 during June and July/ it appeared that summer temperatures in the 

 cold core were similar to those in 1^74, but about 1C warmer than 

 in 1975. 



The pdssaqe of hurricane Relle across the shelf on 9-10 August/ 

 with its center about 100 nTi (185 km) west of where data were 

 collected for this analysis/ was apparently quite influential in 

 coolino and deepening the surface layer south of New England (see 

 discussion of section 9)/ but had no obvious effect on bottom 

 temperatures as seen in the sections. 



FoLlowincj an incursion of Slope Water toward the end of October/ 

 which interrupted the seasonal progression/ Shelf Water cooling 

 at the bottom was rapid to a deoth of 75 m/ and by the end of the 

 year reachec values/ at that lower depth/ about 4C lower than in 

 1974 and 1975. The early breakdown of stratification and strong 

 cooling presumably resulted from unusually cold atmospheric 

 conditions during October and f^ovember following below normal air 

 temperatures during the summer (see Chamberlin and Armstrong/ 

 Paper 11). 



SLoE;e Water Events 



The Slope Water/ a band lying between the Shelf Water and the 

 Gulf Stream and having intermediate temperature values/ is 

 separated from the Shelf Water by a thermal gradient that Wright 

 (1976)/ in an analysis of historical data from 1941 to 1972/ 

 found to have an average midpoint temperature of IOC in the 

 region south of New England/ except for a brief period following 

 the fall overturn when the minimum temperature Shelf Water is 



322 



