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A large-amplitude meander of the shelfbreak front during summer south of New England : observations from the Shelfbreak PRIMER experiment

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Authors
Gawarkiewicz, Glen G.
Brink, Kenneth H.
Bahr, Frank B.
Beardsley, Robert C.
Caruso, Michael J.
Lynch, James F.
Chiu, Ching-Sang
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2004-03-04
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American Geophysical Union
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en_US
Abstract
In order to examine spatial and temporal variability of the shelfbreak front during peak stratification, repeated surveys using a towed undulating vehicle (SeaSoar) are used to describe the evolution of shelfbreak frontal structure during 26 July to 1 August 1996 south of New England. Spatial correlation (e-folding) scales for the upper 60 m of the water column were generally between 8 and 15 km for temperature, salinity, and velocity. Temporal correlation scales were about 1 day. The frontal variability was dominated by the passage of a westward propagating meander that had a wavelength of 40 km, a propagation speed of 0.11 m s−1, and an amplitude of 15 km (30 km from crest to trough). Along-front geostrophic velocities (referenced to a shipboard acoustic Doppler current profilers) were as large as 0.45 m s−1, although subject to significant along-front variations. The relative vorticity within the jet was large, with a maximum 0.6 of the local value of the Coriolis parameter. Seaward of the front, a small detached eddy consisting of shelf water was present with a diameter of approximately 15 km. Ageostrophic contributions to the velocity field are estimated to be as large as 0.3 m s−1 in regions of sharp curvature within the meander. These observations strongly suggest that during at least some time periods, shelfbreak exchange is nonlinear (large Rossby number) and dominated by features on a horizontal scale of order 10 km.
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This work was performed under grants N-00014-95-1-0575 and N-00014-98-1-0059. as part of the ONR Shelfbreak PRIMER Initiative. Some additional analysis and writing was done under ONR grants N-00014-00-1-0931 and N-00014-01-1-0247.
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Journal of Geophysical Research 109 (2004): C03006, doi:10.1029/2002JC001468.
Journal of Geophysical Research 109 (2004): C03006
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