Topocaustics

L. Y. Oey, Y. L. Chang, Z. B. Sun, X. H. Lin

    Research output: Contribution to journalArticlepeer-review

    10 Citations (Scopus)

    Abstract

    Deep (∼2000 m) observations near the Sigsbee escarpment in the Gulf of Mexico show short-period (approximately 5-12 days) energetic currents due to topographic Rossby waves (TRW's). We suggest that the phenomenon is due to the focusing and accumulation of TRW energy by the slopes coupled with a bend in isobaths, in a topographic caustic (topocaustic). The idea draws on a simple mathematical equivalence between the propagation of internal waves and of TRW's. Topocaustics occur near regions of maximum NT = N|∇h| (N = Brunt-Väisälä frequency; h = water depth). Because of the one-sided propagation property of TRW's, energy also tends to accumulate at the "western" end of closed contours of NT. The process is demonstrated here using a nonlinear primitive-equation numerical model with idealized bathymetry and forcing. A Gulf of Mexico simulation initialized with a data-assimilated analysis covering the period of the Sigsbee observation is then conducted. The mooring is near a localized maximum NT, and Intrinsic Mode Functions confirm the existence of energetic bursts of short-period deep-current events. The strong currents are locally forced from above, either by an extended Loop Current or a warm ring.

    Original languageEnglish
    Pages (from-to)277-286
    Number of pages10
    JournalOcean Modelling
    Volume29
    Issue number4
    DOIs
    Publication statusPublished - 2009 Jun 25

    Keywords

    • Deep currents
    • Gulf of Mexico
    • Internal waves
    • Topocaustics
    • Topographic Rossby waves

    ASJC Scopus subject areas

    • Computer Science (miscellaneous)
    • Oceanography
    • Geotechnical Engineering and Engineering Geology
    • Atmospheric Science

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