Freshwater Composition and Connectivity of the Connecticut River Plume During Ambient Flood Tides

The Connecticut River plume interacts with the strong tidal currents of ambient receiving waters in eastern Long Island Sound. formed during flood tides is studied as an example river plumes entering into energetic environments estuaries or continental shelves. Conservative passive freshwater tracers within a high-resolution nested hydrodynamic model are applied to determine how source from different parts cycle contribute composition and interact bounding fronts. connection can be cut off only under low-discharge conditions, when reverse surface flow through mouth after max flood. Upstream extent limited because arrest opposing propagation, internal Froude number exceeds one. downstream always 20 km mouth, which less than twice excursion. Freshwaters preceding ebb oldest found new plume. Connectivity fronts exhibits upstream-to-downstream asymmetry. arrested upstream front has high connectivity, all freshwaters exiting immediately this boundary. lowest overall interaction since younger interior do not overtake front. offshore inshore boundary exhibit progression older decreasing connectivity waters. Plume-averaged tracer concentrations variances both initial growth period followed by longer decay for remainder period. plume-averaged variance increased inputs, decreased entrainment, destroyed mixing. Peak entrainment velocities higher values waters, indicating stronger closer mouth. Entrainment mixing time scales (1–4 h at flood) shorter half period, vigorous enough rapidly diminish