Seasonal variation of residual drift in Long Island Sound

Abstract

Residual drift in Long Island Sound (LIS) is analyzed based on the recovery of 346 out of 951 surface and bottom drifters released at 86 locations in 1973 and 1974. Two periods of distinctly differing drift correlate with wind and freshwater discharge variation. The summer period (June to early November 1973) is characterized by relatively weak southwest winds and low freshwater discharge. In the winter period (after early November 1973) there are strong northwest winds and relatively high freshwater discharge. An estuarine circulation (surface outflow and bottom inflow) exists in eastern LIS throughout the year. Bottom drifter returns received in the summer period indicate that the westward flux of near bottom waters does not extend into central LIS past Mattituck Sill. During the winter season near bottom waters move well into central LIS and upwelling against the Connecticut coast is apparent. There is little evidence for significant near bottom exchange between western and central LIS.