Submesoscale Impacts on Mesoscale Agulhas Dynamics

Schubert, René, Schwarzkopf, Franziska U., Baschek, B. and Biastoch, Arne (In Press / Accepted) Submesoscale Impacts on Mesoscale Agulhas Dynamics Journal of Advances in Modeling Earth Systems . DOI 10.1029/2019MS001724.

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Mesoscale dynamics of the Agulhas Current system determine the exchange between the Indian and Atlantic oceans, thereby influencing the global overturning circulation. Using a series of ocean model experiments compared to observations we show that the representation of mesoscale eddies in the Agulhas ring path improves with increasing resolution of submesoscale flows. Simulated submesoscale dynamics are validated with time‐mean horizontal‐wavenumber spectra from satellite sea‐surface temperature measurements and mesoscale dynamics with spectra from sea‐surface height. While the Agulhas ring path in a non‐submesoscale resolving 1/20° configuration is associated with too less power spectral densities on all scales and too steep spectral slopes, the representation of the mesoscale dynamics improves when the diffusion and the dissipation of the model are reduced and some small‐scale features are resolved. Realistic power spectral densities over all scales are achieved when additionally the horizontal resolution is increased to 1/60° and a larger portion of the submesoscale spectrum is resolved. Results of an eddy‐detection algorithm applied to the model outputs as well as to a gridded sea‐surface height satellite product show that in particular strong cyclones are much better represented when submesoscale flows are resolved by the model. The validation of the submesoscale dynamics with sea‐surface temperature spectra provides guidance for the choice of advection schemes and explicit diffusion and dissipation as well as for further subgrid‐scale parameterizations. For the Agulhas ring path, the use of upstream biased advection schemes without explicit diffusion and dissipation is found to be associated with realistically simulated submesoscales.

Document Type: Article
Additional Information: This article has been accepted for publication and undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process, which may lead to differences between this version and the Version of Record. Please cite this article as doi: 10.1029/2019MS001724
Keywords: submesoscale dynamics; Agulhas; scale‐interaction; spectral analysis; model validation; satellite observations
Research affiliation: OceanRep > GEOMAR > FB1 Ocean Circulation and Climate Dynamics > FB1-OD Ocean Dynamics
Refereed: Yes
DOI etc.: 10.1029/2019MS001724
ISSN: 1942-2466
Date Deposited: 30 Jul 2019 08:48
Last Modified: 30 Jul 2019 08:48

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