Wind Effects on Small-Scale River and Creek Plumes

Date

2022-12-01

Author

Başdurak, Nüvit Berkay
Largier, J.L.

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In contrast to large river plumes, Coriolis effects are weak, and inertia is quickly depleted so that the fate and structure of small-scale plumes are more sensitive to tide and wind. Advected alongshore by reversing tidal currents in absence of wind forcing, small buoyant plumes are persistently deflected downwind in presence of alongshore winds and exhibit little tidal variability. The effect of different upwelling/downwelling winds on buoyant outflows ∼10 m3 s−1 is explored. With increasing wind, tidal variability decreases, as does asymmetry in plume characteristics—for strong winds upwelling/downwelling plume structure is similar as the plume is retained closer to the shore. Wind forcing is exerted directly by wind stress on the surface of the plume and indirectly by wind-driven currents that deflect the upwind boundary of the plume. While inertia and buoyancy dominate the inner plume, and wind dominates the outer plume, the mid-plume responds to an interaction of wind and buoyancy forcing that can be indexed by a Plume Wedderburn Number Wpl (wind stress vs. density gradients): for weaker winds (Wpl 1) surface stress mixes the plume vertically, shortening the reach of low-salinity waters. However, dilute plume waters extend furthest in strong winds, passively advected several kilometers downwind. Shoreline exposure to outflow transitions from a quasi-symmetrical tide-averaged zone of impact under zero-wind to a heavily skewed zone with persistent weak wind and a one-sided zone for strong wind.

Subject Keywords

creek plumes, high resolution river plume dynamics, idealized numerical model, small-scale river plumes, upwelling downwelling winds

URI

https://hdl.handle.net/11511/107633

Collections

Graduate School of Marine Sciences, Article