The response of a baroclinic anticyclonic eddy to relative wind stress forcing

Wilder, T. ORCID: https://orcid.org/0000-0002-1108-4655, Zhai, X., Munday, D. and Joshi, M. (2022) The response of a baroclinic anticyclonic eddy to relative wind stress forcing. Journal of Physical Oceanography, 52 (9). pp. 2129-2142. ISSN 0022-3670 doi: 10.1175/JPO-D-22-0044.1

Abstract/Summary

Including the ocean surface current in the calculation of wind stress is known to damp mesoscale eddies through a negative wind power input, and have potential ramifications for eddy longevity. Here, we study the spin-down of a baroclinic anticyclonic eddy subject to absolute (no ocean surface current) and relative (including ocean surface current) wind stress forcing by employing an idealised high-resolution numerical model. Results from this study demonstrate that relative wind stress dissipates surface mean kinetic energy (MKE) and also generates additional vertical motions throughout the whole water column via Ekman pumping. Wind stress curl-induced Ekman pumping generates additional baroclinic conversion (mean potential to mean kinetic energy) that is found to offset the damping of surface MKE by increasing deep MKE. A scaling analysis of relative wind stress-induced baroclinic conversion and relative wind stress damping confirms these numerical findings, showing that additional energy conversion counteracts relative wind stress damping. What is more, wind stress curl-induced Ekman pumping is found to modify surface potential vorticity gradients that lead to an earlier destabilisation of the eddy. Therefore, the onset of eddy instabilities and eventual eddy decay takes place on a shorter timescale in the simulation with relative wind stress.

Item Type	Article
URI	https://reading-clone.eprints-hosting.org/id/eprint/108512
Identification Number/DOI	10.1175/JPO-D-22-0044.1
Refereed	Yes
Divisions	Science > School of Mathematical, Physical and Computational Sciences > NCAS
Publisher	American Meteorological Society
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