Cross‐shelf transport of freshwater on the New Jersey shelf

Repeated hydrographic surveys off New Jersey about 100 km south of the Hudson River mouth were conducted during spring and summer 2006. Glider observations reveal a strong seasonal variation in the surface salinity. Buoyant water is restricted to an area close to the coast during spring, but spans the entire shelf width during summer. During late July and August, freshwater lenses with large density anomaly are found up to 100 km from the coast. Surface velocity maps, satellite imagery and drifters' trajectories revealed the existence of a jet directed offshore and to the south, from near the river mouth toward the study region. This provides a direct pathway for transporting freshwater and any biogeochemical material it contains, including phytoplankton, dissolved organic and nonalgal particulate matter, across the shelf. The highest frequency of observation of the freshwater lenses offshore occurs when the jet transport is large, and the river discharge is relatively high. The transport in the jet is correlated with upwelling winds on scales of a few days.