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Fluids 2018, 3(2), 32; https://doi.org/10.3390/fluids3020032

Submesoscale Turbulence over a Topographic Slope

California Institute of Technology, 1200E California Blvd., Pasadena, CA 91125, USA
Current address: Israel Oceanographic and Limnological Research, Tel-Shikmona, Haifa 31080, Israel.
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Received: 27 December 2017 / Revised: 29 April 2018 / Accepted: 2 May 2018 / Published: 7 May 2018
(This article belongs to the Collection Geophysical Fluid Dynamics)
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Abstract

Regions of the ocean near continental slopes are linked to significant vertical velocities caused by advection over a sloping bottom, frictional processes and diffusion. Oceanic motions at submesoscales are also characterized by enhanced vertical velocities, as compared to mesoscale motions, due to greater contributions from ageostrophic flows. These enhanced vertical velocities can make an important contribution to turbulent fluxes. Sloping topography may also induce large-scale potential vorticity gradients by modifying the slope of interior isopycnal surfaces. Potential vorticity gradients, in turn, may feed back on mesoscale stirring and the generation of submesoscale features. In this study, we explore the impact of sloping topography on the characteristics of submesoscale motions. We conduct high-resolution (1 km × 1 km) simulations of a wind-driven frontal current over an idealized continental shelf and slope. We explore changes in the magnitude, skewness and spectra of surface vorticity and vertical velocity across different configurations of the topographic slope and wind-forcing orientations. All of these properties are strongly modulated by the background topography. Furthermore, submesoscale characteristics exhibit spatial variability across the continental shelf and slope. We find that changes in the statistical properties of submesoscale motions are linked to mesoscale stirring responding to differences in the interior potential vorticity distributions, which are set by frictional processes at the ocean surface and over the sloping bottom. Improved parameterizations of submesoscale motions over topography may be needed to simulate the spatial variability of these features in coarser-resolution models, and are likely to be important to represent vertical nutrient fluxes in coastal waters. View Full-Text
Keywords: turbulence; submesoscale; topography; slope; potential vorticity turbulence; submesoscale; topography; slope; potential vorticity
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).
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Lazar, A.; Zhang, Q.; Thompson, A.F. Submesoscale Turbulence over a Topographic Slope. Fluids 2018, 3, 32.

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