Instability and Mixing of Zonal Jets along an Idealized Continental Shelf Break
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Stern-2015-Instability and Mixi.pdf
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4.99 MB
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Author(s)
Stern, Alon
Nadeau, Louis-Philippe
Holland, David
Date Issued
September 2015
Journal
Journal of Physical Oceanography
Publisher
American Meteorological Society
Citation
Stern, Alon, Louis-Philippe Nadeau, and David Holland. “Instability and Mixing of Zonal Jets Along an Idealized Continental Shelf Break.” Journal of Physical Oceanography 45, no. 9 (September 2015): 2315–2338. © 2015 American Meteorological Society
Version
Final published version
Abstract
The interaction between an Antarctic Circumpolar Current–like channel flow and a continental shelf break is considered using eddy-permitting simulations of a quasigeostrophic and a primitive equation model. The experimental setup is motivated by the continental shelf of the West Antarctic Peninsula. Numerical experiments are performed to study how the width and slope of an idealized continental shelf topography affect the characteristics of the flow. The main focus is on the regime where the shelfbreak width is slightly greater than the eddy scale. In this regime, a strong baroclinic jet develops on the shelf break because of the locally stabilizing effect of the topographic slope. The velocity of this jet is set at first order by the gradient of the background barotropic geostrophic contours, which is dominated by the slope of the topography. At statistical equilibrium, an aperiodic cycle is observed. Initially, over a long stable period, an upper-layer jet develops over the shelf break. Once the vertical shear reaches the critical condition for baroclinic instability, the jet becomes unstable and drifts away from the shelf break. The cross-shelf mixing is intrinsically linked with the jet drifting, as most of the meridional flux occurs during this instability period. Investigation of the zonal momentum budget reveals that a strong Reynolds stress divergence inversion across the jet is associated with a drifting event, accelerating one flank of the jet and decelerating the other. The hypothesis that jet drifting may be due to one flank of the jet being more baroclinically unstable than the other is tested using topographic profiles with variable curvatures.
MIT Department
Massachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences
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Article is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use.
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DOI of Published Version
https://doi.org/10.1175/jpo-d-14-0213.1
