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Abstract In the surfzone, breaking‐wave generated eddies and vortices transport material along the coast and offshore to the continental shelf, providing a pathway from land to the ocean. Here, surfzone vorticity is investigated with unique field observations obtained during a wide range of wave and bathymetric conditions on an Atlantic Ocean beach. Small spatial‐scale [O(10 m)] vorticity estimated with a 5 m diameter ring of 14 current meters deployed in ∼2 m water depth increased as the directional spread of the wave field increased. Large spatial‐scale [O(100 m)] vorticity calculated from remote sensing estimates of currents across the surfzone along 200 m of the shoreline increased as alongshore bathymetric variability (channels, bars, bumps, holes) increased. For all bathymetric conditions, large‐scale vorticity in the inner surfzone was more energetic than in the outer surfzone.
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Diagnosing surfzone impacts on inner-shelf flow spatial variability using realistic model experiments with and without surface gravity waves
Abstract Rip currents are generated by surfzone wave breaking and are ejected offshore inducing inner-shelf flow spatial variability (eddies). However, surfzone effects on the inner-shelf flow spatial variability have not been studied in realistic models that include both shelf and surfzone processes. Here, these effects are diagnosed with two nearly identical twin realistic simulations of the San Diego Bight over summer to fall where one simulation includes surface gravity waves (WW) and the other that does not (NW). The simulations include tides, weak to moderate winds, internal waves, submesoscale processes, and have surfzone width L sz of 96(±41) m (≈ 1 m significant wave height). Flow spatial variability metrics, alongshore root mean square vorticity, divergence, and eddy cross-shore velocity, are analyzed in a L sz normalized cross-shore coordinate. At the surface, the metrics are consistently (> 70%) elevated in the WW run relative to NW out to 5 L sz offshore. At 4 L sz offshore, WW metrics are enhanced over the entire water column. In a fixed coordinate appropriate for eddy transport, the eddy cross-shore velocity squared correlation betweenWWand NW runs is < 0.5 out to 1.2 km offshore or 12 time-averaged L sz . The results indicate that the eddy tracer ( e.g. , larvae) transport and dispersion across the inner-shelf will be significantly different in the WW and NW runs. The WW model neglects specific surfzone vorticity generation mechanisms. Thus, these inner-shelf impacts are likely underestimated. In other regions with larger waves, impacts will extend farther offshore.
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- PAR ID:
- 10411723
- Date Published:
- Journal Name:
- Journal of Physical Oceanography
- ISSN:
- 0022-3670
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1175/JPO-D-20-0324.1
