1. Wind‐Enhanced Separation of Large‐Scale River Plumes From Coastal Corners.
- Author
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Whitney, Michael M.
- Subjects
REGIONS of freshwater influence ,BULGING (Metalwork) ,WIND pressure ,COMPUTER simulation ,FRESH water - Abstract
Idealized models are analyzed to quantify how large‐scale river plumes interact with coastal corners with and without wind‐driven currents. The configuration has a corner formed by two perpendicular shelves (with constant slope) that are joined with a coastal radius of curvature (rc). The buoyant plume originates from an upstream point source. The rc and wind forcing are varied among runs. Steep‐ and gentle‐slope runs are compared for some situations. Without winds, plumes separate from corners with rc smaller than two inertial radii (ri); this threshold is twice the rc < ri theoretical separation criterion. After separation, no‐wind plumes form an anticyclonic bulge, and reattach farther downstream. Offshore excursion increases as rc decreases. A downwelling‐favorable wind component along the upstream coast (τsx) favors separation by increasing total plume speed. An upwelling‐favorable wind component along the downstream coast (τsy) also increases offshore excursion. Winds blowing obliquely offshore with both these wind components advect the plume farther offshore. Wind‐driven currents that steer plumes in this situation include a downshelf jet originating on the upstream shelf and continuing around the coastal corner and beyond, offshore and upshelf surface transport downstream of the corner, and surface Ekman transport on the outer shelf. Multiple linear regressions quantify plume position sensitivity to rc, τsx, and τsy; results are discussed in a dynamical context. Globally, many river plumes interact with coastal corners under various wind conditions. Plain Language Summary: Freshwater from rivers can form long plumes that flow along the coast far from river mouths. When these plumes reach a sharp coastal corner, like the tip of a peninsula, the flow can detach from the coast and carry freshwater far offshore. This study applies a computer model to study river plume behavior at perpendicular coastal corners with and without wind influences. Without winds, plumes separate from the most tightly turning corners, form a bulge, and reattach to the coast farther downstream. Flows forced by winds are important in steering river plumes. Plume waters move farthest offshore when winds blow obliquely away from the coastal corner. Globally, many river plumes interact with coastal corners and wind influence can enhance offshore transport of freshwater in these areas. Key Points: Without winds, plumes separate from corners turning more tightly than two inertial radii, form a bulge, and reattach farther downstreamOffshore plume excursion is maximized when winds blow obliquely away from the coastal cornerWind‐driven flow favoring offshore plume transport includes a downshelf jet and offshore and upshelf transport downstream of the corner [ABSTRACT FROM AUTHOR]
- Published
- 2024
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