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This study investigates the dispersal of the Hudson River outflow across the New York Bight and the adjacent inner- through midshelf region. Regional Ocean Modeling System (ROMS) simulations were used to examine the mean momentum dynamics; the freshwater dispersal pathways relevant to local biogeochemical processes; and the contribution from wind, remotely forced along-shelf current, tides, and the topographic control of the Hudson River shelf valley. The modeled surface currents showed many similarities to the surface currents measured by high-frequency radar [the Coastal Ocean Dynamics Applications Radar (CODAR)]. Analysis shows that geostrophic balance and Ekman transport dominate the mean surface momentum balance, with most of the geostrophic flow resulting from the large-scale shelf circulation and the rest being locally generated. Subsurface circulation is driven principally by the remotely forced along-shelf current, with the exception of a riverward water intrusion in the Hudson River shelf valley. The following three pathways by which freshwater is dispersed across the shelf were identified: (i) along the New Jersey coast, (ii) along the Long Island coast, and (iii) by a midshelf offshore pathway. Time series of the depth-integrated freshwater transport show strong seasonality in dispersal patterns: the New Jersey pathway dominates the winter–spring seasons when winds are downwelling favorable, while the midshelf pathway dominates summer months when winds are upwelling favorable. A series of reduced physics simulations identifies that wind is the major force for the spreading of freshwater to the mid- and outer shelf, that remotely forced along-shelf currents significantly influence the ultimate fate of the freshwater, and that the Hudson River shelf valley has a modest dynamic effect on the freshwater spreading. [ABSTRACT FROM AUTHOR]

The dispersal of the Hudson River plume in response to idealized wind forcing is studied using a three-dimensional model. The model domain includes the Hudson River and its estuary, with a realistic coastline and bottom topography of the New York Bight. Steady low river discharge typical of mean conditions and a high-discharge event representative of the spring freshet are considered. Without wind forcing the plume forms a southward coastally trapped current at low river discharge and a large recirculating bulge of low-salinity water during a high-discharge event. Winds affect the freshwater export through the mouth of the estuary, which is the trajectory the plume takes upon entering the waters of the Mid-Atlantic Bight inner shelf, and the rate at which freshwater drains downstream. The dispersal trajectory is also influenced by the particular geography of the coastline in the apex of the New York Bight. Northward wind causes offshore displacement of a previously formed coastally trapped plume and drives a new plume along the Long Island coast. Southward wind induces a strong coastal jet that efficiently drains freshwater to the south. Eastward wind aids freshwater export from the estuary and favors the accumulation of freshwater in the recirculating bulge outside the mouth of Raritan Bay. Westward wind delays freshwater export from Raritan Bay. The momentum balance of the modeled plume shows that buoyancy and wind forces largely determine the pattern of horizontal freshwater dispersal, including the spreading of freshwater over ambient, more saline water and the bulge formation. [ABSTRACT FROM AUTHOR]