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Low frequency variability of Southern Ocean jets

Thompson, Andrew F. and Richards, Kelvin J. (2011) Low frequency variability of Southern Ocean jets. Journal of Geophysical Research C, 116 . C09022. ISSN 0148-0227.

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Both observations and high resolution numerical models show that the Southern Ocean circumpolar flow is concentrated in a large number (approximately 8 to 12) of narrow filamentary jets. It is shown here that coherent jets exhibit a range of low frequency variability, on timescales of months to years, that can lead to displacement and to intermittent formation and dissipation of jets. Using output from an eddy-resolving ocean general circulation model in local regions near topographic features, the impact of energy exchange between eddy and mean flow components on jet persistence and variability is examined. A novel approach that uses a time-dependent definition of the mean flow provides a clearer picture of eddy-mean flow interactions in regions with spatially and temporally varying flow structure. The dynamics are largely consistent with those in idealized quasi-geostrophic models, including topographically-organized and surface-enhanced Reynolds stress forcing of the mean flow. Jets form during periods of enhanced eddy activity, but may persist long after the eddy activity has decayed. Similarly, jets may evolve in a downstream sense, with jet formation localized near topography and undergoing modification in response to changing bathymetry. The evolution of both temperature and potential vorticity is used to show that the low-frequency variability of the jets impacts water mass structure and tracer transport. This study highlights various examples of Southern Ocean dynamics that will prove difficult to capture through parameterizations in coarser climate models.

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Thompson, Andrew F.0000-0003-0322-4811
Additional Information:© 2011 American Geophysical Union. Received 26 October 2010; revised 11 June 2011; accepted 23 June 2011; published 20 September 2011. The authors gratefully acknowledge the provision of OFES output by Hideharu Sasaki. We thank two reviewers for their comments, which significantly improved this manuscript. We also acknowledge helpful conversations with Chris Wilson. AFT was supported by a NERC postdoctoral fellowship, NE/E013171/1.
Funding AgencyGrant Number
Natural Environment Research Council (NERC)NE/E013171/1
Subject Keywords:Antarctic Circumpolar Current; Southern Ocean; fronts; jets; potential vorticity; topography
Record Number:CaltechAUTHORS:20111025-085916664
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Official Citation:Thompson, A. F., and K. J. Richards (2011), Low frequency variability of Southern Ocean jets, J. Geophys. Res., 116, C09022, doi:10.1029/2010JC006749.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:27398
Deposited By: Jason Perez
Deposited On:25 Oct 2011 20:13
Last Modified:03 Oct 2019 03:23

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