Temperature and salt balances on Georges Bank February–August 1995

Abstract

Temperature and salinity variability over the crest and southern flank of Georges Bank are investigated using moored observations obtained from February to August 1995 and historical data. There was a large seasonal variation in water temperature, which decreased 1°C–2°C in February to a minimum of 5°C due to surface cooling and wind‐forced cross‐bank advection, and then increased steadily due to surface heating, reaching 10°C (southern flank) to 17°C (crest) in August. The crest warmed more than the southern flank because it is shallower. Temperature variability at shorter timescales (days to weeks) was primarily due to surface heating on the crest and horizontal advection on the southern flank. Salinity variability over the southern flank was primarily associated with two processes. Intrusions of warm, salty, shelf‐slope‐front water in May and August were associated with Gulf Stream warm‐core rings, but did not cause longer‐term changes on the southern flank or penetrate onto the crest. Alongbank advection brought low‐salinity, cool Scotian Shelf Water to the southern flank sites in March and early May, about three weeks after crossing the Northeast Channel onto the northeastern flank of Georges Bank (≈130 km away). This low‐salinity water on the southern flank in the spring did not penetrate immediately onto the crest. Instead, the crest salinity steadily decreased from April to August due to both precipitation (evaporation was small) and, based on historical data, a tidally forced, cross‐frontal exchange flow (0.01–0.02 m s−1) that both freshens and cools the crest.