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Energetic Submesoscale Dynamics in the Ocean Interior

Siegelman, Lia (2020) Energetic Submesoscale Dynamics in the Ocean Interior. Journal of Physical Oceanography, 50 (3). pp. 727-749. ISSN 0022-3670.

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Submesoscale ocean processes, characterized by order-1 Rossby and Richardson numbers, are currently thought to be mainly confined to the ocean surface mixed layer, whereas the ocean interior is commonly assumed to be in quasigeostrophic equilibrium. Here, a realistic numerical simulation in the Antarctic Circumpolar Current, with a 1/48° horizontal resolution and tidal forcing, is used to demonstrate that the ocean interior departs from the quasigeostrophic regime down to depths of 900 m, that is, well below the mixed layer. Results highlight that, contrary to the classical paradigm, the ocean interior is strongly ageostrophic, with a pronounced cyclone–anticyclone asymmetry and a dominance of frontogenesis over frontolysis. Numerous vortices and filaments, from the surface down to 900 m, are characterized by large Rossby and low Richardson numbers, strong lateral gradients of buoyancy, and vigorous ageostrophic frontogenesis. These deep submesoscales fronts are only weakly affected by internal gravity waves and drive intense upward vertical heat fluxes, consistent with recent observations in the Antarctic Circumpolar Current and the Gulf Stream. As such, deep submesoscale fronts are an efficient pathway for the transport of heat from the ocean interior to the surface, suggesting the presence of an intensified oceanic restratification at depth.

Item Type:Article
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URLURL TypeDescription Information
Siegelman, Lia0000-0003-3330-082X
Additional Information:© 2020 American Meteorological Society. Manuscript received 24 October 2019, in final form 28 December 2019. Thanks are given to Patrice Klein for his wise and always inspiring advices and to Andrew F. Thompson for stimulating discussions. Thanks are also given to Hector S. Torres for his invaluable assistance in navigating the tricks of NASA Advanced Supercomputing (NAS), to Dimitris Menemenlis for running the LLC4320 simulation, to Christopher Henze at NASA Ames Hyperwall, and to the MITgcm developers and NAS scientists that made available the model outputs. This research was carried out, in part, at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with NASA. Author Siegelman is a NASA-JVSRP affiliate and is supported by a joint CNES–Région Bretagne doctoral fellowship. High-end computing resources for the numerical simulation were provided by the NAS Division at the Ames Research Center.
Funding AgencyGrant Number
Centre National d’Études Spatiales (CNES)UNSPECIFIED
Région BretagneUNSPECIFIED
Subject Keywords:Ageostrophic circulations; Eddies; Frontogenesis/frontolysis; Mesoscale processes; Ocean dynamics; Potential vorticity
Issue or Number:3
Record Number:CaltechAUTHORS:20200416-133244080
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:102582
Deposited By: Tony Diaz
Deposited On:16 Apr 2020 20:50
Last Modified:16 Apr 2020 20:50

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