Circulation On the Continental Shelf of the Southeastern United States. Part I: Subtidal Response to Wind and Gulf Stream Forcing During Winter

Abstract

Abstract Subtidal current and sea level response to wind and Gulf Stream forcing are investigated for the South Atlantic Bight shelf during winter conditions. Low-frequency flow variability in the outer shelf results primarily from wavelike meanders and eddies in the Gulf Stream front that occur in a 2-day to 2-week period band. Current meter derived vertically integrated momentum balances indicated that these large amplitude flow events are in approximate geostrophic balance with baroclinic pressure gradients induced by northward propagating Gulf Stream disturbances. Low-frequency flow at midshelf is primarily a local Ekman response to wind forcing. Cross-shelf momentum balance for the total water column is between the along-shelf geostrophic current and the cross-shelf barotropic pressure gradient resulting from wind induced sea level changes at the coast. This balance holds for both mean and fluctuating parts of the flow, with the along-shelf barotropic current lagging sea level by 6 to 12 hours and al...