Surface Ocean Enstrophy, Kinetic Energy Fluxes and Spectra from Satellite Altimetry

Hemant Khatri, Jai Sukhatme, Abhishek Kumar, Mahendra K. Verma

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    Abstract

    Enstrophy, kinetic energy (KE) fluxes and spectra are estimated in different parts of the mid-latitudinal oceans via altimetry data. To begin with, using geostrophic currents derived from sea-surface height anomaly data provided by AVISO, we confirm the presence of a strong inverse flux of surface KE at scales larger than approximately 250 km. We then compute enstrophy fluxes to help develop a clearer picture of the underlying dynamics at smaller scales, i.e., 250 km to 100 km. Here, we observe a robust enstrophy cascading regime, wherein the enstrophy shows a large forward flux and the KE spectra follow an approximate $k^{-3.5}$ power-law. Given the rotational character of the flow, not only is this large scale inverse KE and smaller scale forward enstrophy transfer scenario consistent with expectations from idealized studies of three-dimensional rapidly-rotating and strongly-stratified turbulence, it also agrees with detailed analyses of spectra and fluxes in the upper level midlatitude troposphere. Decomposing the currents into components with greater and less than 100 day variability (referred to as seasonal and eddy, respectively), we find that, in addition to the eddy-eddy contribution, the seasonal-eddy and seasonal-seasonal fluxes play a significant role in the inverse (forward) flux of KE (enstrophy) at scales larger (smaller) than about 250 km. Taken together, we suspect, it is quite possible that, from about 250 km to 100 km, the altimeter is capturing the relatively steep portion of a surface oceanic counterpart of the upper tropospheric Nastrom-Gage spectrum.
    Original languageEnglish
    Pages (from-to)3875-3892
    Number of pages18
    JournalJournal of Geophysical Research: Oceans
    Volume123
    Issue number5
    DOIs
    Publication statusPublished - 4 May 2018

    Bibliographical note

    This is the peer reviewed version of the following article: Khatri, H, Sukhatme, J, Kumar, A & Verma, MK 2018, 'Surface Ocean Enstrophy, Kinetic Energy Fluxes and Spectra from Satellite Altimetry' Journal of Geophysical Research: Oceans, vol. 123, no. 5, pp. 3875-3892, which has been published in final form at https://dx.doi.org/10.1029/2017JC013516

    This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.

    Keywords

    • physics.ao-ph

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