The Physical Oceanography Processes in the Hudson River Estuary

W. Rockwell Geyer and Robert Chant abstract The Hudson River has the attributes of a typical, partially mixed estuary - a moderate salinity gradient, significant vertical stratification, and a vigorous, two-layer circulation regime. Yet it also displays considerable variability, both in space and in time. In its northern reaches, the estuary becomes a tidal river, with no trace of oceanic salt but vigorous tidal currents. The salinity intrusion extends 100 kilometers (km) into the estuary during low discharge conditions, but it retreats to within 25 km of New York Harbor during the high river flows of the spring freshet. Fortnightly variations of tidal amplitude also result in pronounced variations in the estuarine regime, becoming well-mixed during strong spring tides and highly stratified during the weakest neaps. At the mouth of the Hudson is a complex network of tidal channels that link the es-tuarine regime of the Hudson to Long Island Sound, Newark Bay, and the Atlantic Ocean. The influence of the Hudson extends into the Mid-Atlantic Bight in the form of a low-salinity plume, which forms a coastal current and flows south along the New Jersey shore during favorable wind-forcing conditions.

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