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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. Thercand wind forcing are varied among runs. Steep‐ and gentle‐slope runs are compared for some situations. Without winds, plumes separate from corners withrcsmaller than two inertial radii (ri); this threshold is twice therc < ritheoretical separation criterion. After separation, no‐wind plumes form an anticyclonic bulge, and reattach farther downstream. Offshore excursion increases asrcdecreases. 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 torc,τsx, andτsy; results are discussed in a dynamical context. Globally, many river plumes interact with coastal corners under various wind conditions.
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Circulation and Retention of River Plumes Around Capes
Abstract River plumes often interact with capes in the coastal ocean, impacting local hydrodynamics and the transport of scalars. However, our current knowledge on how capes affect river plume separation, mixing, and retention is limited. Here, we conducted idealized numerical experiments with Gaussian‐shaped capes of varying curvature radii, constant river discharge, a sloping bottom, and scenarios with and without downwelling winds. We found that river plumes separate from capes when the Rossby number is above 1, a criterion that had not been tested for plume separation. This Rossby number is based on the plume velocity, the Coriolis factor, and the radius of curvature of the cape. Freshwater accumulation is greatest at the lee of narrow (i.e., pointy) capes under calm winds, but decreases significantly in downwelling winds or around broader capes.
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- PAR ID:
- 10499621
- Publisher / Repository:
- DOI PREFIX: 10.1029
- Date Published:
- Journal Name:
- Journal of Geophysical Research: Oceans
- Volume:
- 129
- Issue:
- 4
- ISSN:
- 2169-9275
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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