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Title

Divergent eddy heat fluxes in the Kuroshio Extension at 144°-148°E. Part I: Mean structure

Abstract

The Kuroshio Extension System Study (KESS) provided 16 months of observations to quantify eddy heat flux (EHF) from a mesoscale-resolving array of current- and pressure-equipped inverted echo sounders (CPIES). The mapped EHF estimates agreed well with point in situ measurements from subsurface current meter moorings. Geostrophic currents determined with the CPIES separate the vertical structure into an equivalent-barotropic internal mode and a nearly depth-independent external mode measured in the deep ocean. As a useful by-product of this decomposition, the divergent EHF (DEHF) arises entirely from the correlation between the external mode and the upper-ocean thermal front. EHFs associated with the internal mode are completely rotational. DEHFs were mostly downgradient and strongest just upstream of a mean trough at ~147°E. The downgradient DEHFs resulted in a mean-to-eddy potential energy conversion rate that peaked midthermocline with a magnitude of 10 × 10⁻³ cm² s⁻³ and a depth-averaged value of 3 × 10⁻³ cm² s⁻³. DEHFs were vertically coherent, with subsurface maxima exceeding 400 kW m⁻² near 400-m depth. The subsurface maximum DEHFs occurred near the depth where the quasigeostrophic potential vorticity lateral gradient changes sign from one layer to the next below it. The steering level is deeper than this depth of maximum DEHFs. A downgradient parameterization could be fitted to the DEHF vertical structure with a constant eddy diffusivity κ that had values of 800-1400 m2 s⁻¹ along the mean path. The resulting divergent meridional eddy heat transport across the KESS array was 0.05 PW near 35.25°N, which may account for ~⅓ of the total Pacific meridional heat transport at this latitude.

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http://n2t.net/ark:/85065/d70v8dpq

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eng

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geoscientificInformation

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publication

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2016-01-01T00:00:00Z

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2013-08-01T00:00:00Z

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Copyright 2013 American Meteorological Society (AMS). Permission to use figures, tables, and brief excerpts from this work in scientific and educational works is hereby granted provided that the source is acknowledged. Any use of material in this work that is determined to be "fair use" under Section 107 or that satisfies the conditions specified in Section 108 of the U.S. Copyright Law (17 USC, as revised by P.L. 94-553) does not require the Society's permission. Republication, systematic reproduction, posting in electronic form on servers, or other uses of this material, except as exempted by the above statements, requires written permission or license from the AMS. Additional details are provided in the AMS Copyright Policies, available from the AMS at 617-227-2425 or amspubs@ametsoc.org. Permission to place a copy of this work on this server has been provided by the AMS. The AMS does not guarantee that the copy provided here is an accurate copy of the published work.

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OpenSky Support

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UCAR/NCAR - Library

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