Topocaustics

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

Research output: Contribution to journalArticle

8 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

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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

Cite this

Oey, L. Y., Chang, Y. L., Sun, Z. B., & Lin, X. H. (2009). Topocaustics. Ocean Modelling, 29(4), 277-286. https://doi.org/10.1016/j.ocemod.2009.05.006