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Abstract Numerous eddies in the coastal ocean may experience distortion due to interactions with the ambient flow. Here we investigate how coastal submesoscale eddy distortion affects the cross‐shore and vertical tracer transport using a high‐resolution, wave‐current coupled model in the La Jolla Canyon region within the Southern California Bight. Model dye is released representing freshwater discharges. Model validations show that the coupled model has weaker stratification and weaker currents. Analyses primarily focus on an eddy‐induced cross‐shore dye transport event. The results show that, the coastal eddy is squeezed in the alongshore direction and extends in the cross‐shore direction, driving cross‐shore dye transport. Along a mid‐shelf boundary, the total cross‐shore transport is found to be dominated by the along‐boundary perturbation flow, which is linked to the eddy distortion. In addition, this coastal eddy also possesses vigorous vertical motions. The vertical velocity is more negative on the eddy northern side, favoring local dye subduction. This N‐S vertical velocity asymmetry may largely be induced by the topographic beta effect and the weaker modeled stratification may strengthen this effect. Overall, coastal eddy distortion contributes to the offshore tracer transport and induces spatially non‐uniform vertical dye flux.
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This content will become publicly available on May 1, 2026
Semidiurnal Inner Shelf Flow in the Southern California Bight
Abstract Semidiurnal variability of alongshore currents on the inner shelf of the Southern California Bight is investigated using a 7‐year velocity and pressure time series. Analysis reveals that the ‐frequency alongshore current varies significantly over spatial scales of O(10 km), inconsistent with the expected progressive surface tide. Instead, the observed variability is attributed to the influence of a northward‐propagating, superinertial baroclinic coastal trapped wave (CTW) that generates a quasi‐barotropic flow, defined as the portion of the depth‐averaged alongshore current that is not directly driven by the surface tide. A superinertial CTW model, forced by realistic bathymetry and stratification conditions, suggests that the dominant mode of variability is likely a mode‐1 CTW with a wavelength of approximately 40 km. The observations and model also reveal that seasonal changes in stratification modulate the wavelength and phase speed of the CTW, leading to a seasonal pattern in the phasing of the quasi‐barotropic alongshore flow. These findings provide a new perspective on the complex dynamics governing semidiurnal variability of alongshore currents on the inner shelf of the Southern California Bight and highlight the importance of considering the effects of superinertial CTWs when examining coastal dynamics.
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- Award ID(s):
- 2220439
- PAR ID:
- 10630997
- Publisher / Repository:
- American Geophysical Union
- Date Published:
- Journal Name:
- Journal of Geophysical Research: Oceans
- Volume:
- 130
- Issue:
- 5
- ISSN:
- 2169-9275
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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