The Coastal Sea-Level Response to Wind Stress in the Middle Atlantic Bight

Abstract

Analysis of 40 years of tide gauge data and reanalysis wind stresses from the Middle Atlantic Bight (MAB) indicate that along-shelf wind stresses are a dominant driver of coastal dynamic sea level (sea level plus atmospheric pressure) variability at daily to yearly time scales. The sea-level response to along-shelf wind stress varies substantially along the coast and is accurately reproduced by a steady, barotropic, depth-averaged model (Csanady, 1978, https://doi.org/10.1175/1520-0485(1978)008<0047:tatw>2.0.co;2, Arrested Topographic Wave). The model indicates that the sea-level response in the MAB depends primarily on the along-shelf distribution of the along-shelf wind stress, the Coriolis frequency, the bottom drag coefficient, and the cross-shelf bottom slope. The along-shelf wind stress varies along the MAB shelf due primarily to changes in the shelf orientation. The sea-level response depends on both the local and upstream (in the sense of Kelvin wave propagation) along-shelf wind stresses. Consequently, sea-level variability at daily, monthly and yearly time scales along much of the central MAB coast is more strongly driven by upstream winds along the southern New England shelf than by local winds along the central MAB shelf. The residual coastal sea-level variability, after removing the wind-driven response and the trend, is roughly uniform along the MAB coast. The along-coast average of the residual sea level at monthly and yearly time scales is caused by variations in shelf water densities primarily associated with the large annual cycle in water temperature and interannual variations in salinity.