Diagnosing a meander of the shelf break current in the Middle Atlantic Bight

Robert S. Pickart, Daniel J. Torres, Theresa K. McKee, Michael J. Caruso, Jennifer E. Przystup

Research output: Contribution to journalArticlepeer-review

23 Scopus citations

Abstract

Two wintertime hydrographic crossings of the shelf break current in the Middle Atlantic Bight are analyzed. Separated by 3 days, the two sections sampled opposite phases of a meander of the current. The shipboard acoustic Doppler current profiler (ADCP) data reveal a strong, convergent jet during the first crossing, transporting 0.32 Sv of water equatorward. During the second crossing the transport is the same but the jet is weak and divergent. The measured Rossby numbers imply that the jet is significantly nonlinear in the convergent state. The associated potential vorticity Q distributions differ substantially; the core of the weak jet is characterized by a region of uniform Q, whereas the strong jet contains no such feature. Surface thermal imagery indicates that the leading edge of a steep meander trough was sampled during the first crossing, followed by a broad crest during the second crossing. This is consistent with the convergent versus divergent nature of the flow in the two sections. A nearby Gulf Stream ring likely caused the steepening of the trough. After integrating the spatially low-passed thermal wind shear, the resulting geostrophic sections are compared to the similarly low-passed ADCP fields. This, together with the scales of the meander deduced from the surface imagery, indicates that the trough was in gradient wind balance, whereas the crest was predominantly geostrophic. These observations are consistent with the structure and dynamics of modeled baroclinic jets.

Original languageEnglish (US)
Article number1998JC900066
Pages (from-to)3121-3132
Number of pages12
JournalJournal of Geophysical Research: Oceans
Volume104
Issue numberC2
DOIs
StatePublished - Feb 15 1999
Externally publishedYes

ASJC Scopus subject areas

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

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