A tale of two eddies

Diagnosing coherent eddies through acoustic remote sensing

T. Rossby, C. Flagg, P. Ortner, C. Hu

Research output: Contribution to journalArticle

9 Citations (Scopus)

Abstract

A 38 kHz vessel-mounted acoustic Doppler current profiler is used to explore in detail the dynamics of an anticyclonic and a cyclonic eddy during two transits of the cruise vessel Explorer of the Seas from the Caribbean to New Jersey in July 2007. The radial scale of the two eddies is similar, but whereas the cyclone is strongly surface intensified, the anticyclone has its maximum expression with near-solid body rotation between 200 and 800 m depth. The anticyclone has a minimum in relative vorticity very close to-f at 800 m depth and the cyclone has a maximum of about +1.6 f close to the surface where f is the local Coriolis parameter. By integrating the momentum equation the geopotential anomaly field and hence the potential energy of the eddies can be determined quite accurately, which means that the kinetic and potential energy of the eddies can be determined purely through acoustic remote sensing. Given a density profile just outside the eddy one can integrate the gradient wind equation to obtain an estimate of the density and hence potential vorticity fields through the two eddies. The acoustic backscatter patterns in the eddies are quite distinct from the surrounding waters. The backscatter intensity of the main scattering layer at ∼600 m depth decreases by ∼10 dB in the core of both eddies. In the cyclonic eddy three identifiable scattering layers in the main thermocline show a strong tendency for the scattering layer to track the shoaling density structure toward the center of the eddy.

Original languageEnglish
Article numberC12017
JournalJournal of Geophysical Research: Oceans
Volume116
Issue number12
DOIs
StatePublished - Jan 1 2011

Fingerprint

remote sensing
Remote sensing
eddy
acoustics
Acoustics
Scattering
vortices
Potential energy
Vorticity
Kinetic energy
anticyclones
Momentum
Temperature distribution
cyclones
anticyclone
scattering
potential energy
Water
cyclone
vorticity

ASJC Scopus subject areas

  • Geochemistry and Petrology
  • Geophysics
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science
  • Oceanography

Cite this

A tale of two eddies : Diagnosing coherent eddies through acoustic remote sensing. / Rossby, T.; Flagg, C.; Ortner, P.; Hu, C.

In: Journal of Geophysical Research: Oceans, Vol. 116, No. 12, C12017, 01.01.2011.

Research output: Contribution to journalArticle

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