A near-inertial mode observed within a Gulf Stream warm-core ring

Type Article
Date 2013-04
Language English
Author(s) Joyce Terrence M.1, Toole John M.1, Klein Patrice2, Thomas Leif N.3
Affiliation(s) 1 : Woods Hole Oceanog Inst, Woods Hole, MA 02543 USA.
2 : IFREMER, Lab Phys Oceans, Plouzane, France.
3 : Stanford Univ, Dept Environm Earth Syst Sci, Stanford, CA 94305 USA.
Source Journal Of Geophysical Research-oceans (0148-0027) (Amer Geophysical Union), 2013-04 , Vol. 118 , N. 4 , P. 1797-1806
DOI 10.1002/jgrc.20141
WOS© Times Cited 33
Keyword(s) near-inertial waves, warm-core ring, velocity fine structure
Abstract Layering of ocean velocity fine structure has been coherently observed across the entire extent of a Gulf Stream warm-core ring using a shipboard acoustic Doppler current profiler system in September 2009 and independently sampled as the ring transited a moored array. Lines of constant velocity phase generally followed isopycnals as they deepened within the ring center. We also observed a clear separation of the vertical structure of the flows associated with the ring (of order 0.5m/s) with the shorter (200m) and less energetic (similar to 0.2m/s) flows of the velocity fine structure, which was further observed to rotate clockwise with increasing depth, consistent with downward propagating near-inertial waves (NIWs). Observations are consistent with a ring-scale NIW packet, probably wind forced, that shows enhanced NIW energy within the sloping pycnocline at depths of 300-700m. Evidence of wind-forced NIWs within anticylonic eddies in a numerical simulation shows some similar features to our observations, which we try to understand physically with basic WKB-type wave/current dynamics along the lines of previously published work and a new calculation of NIW trapping within an isolated, baroclinic vortex.
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