Geostrophic Adjustment Problems in a Polar Basin

Luneva, Maria V.; Willmott, Andrew J.; Maqueda, Miguel Angel Morales. 2012 Geostrophic Adjustment Problems in a Polar Basin. Atmosphere-Ocean, 50 (2). 134-155.

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This is an Accepted Manuscript of an article published by Taylor & Francis in Atmosphere-Ocean on 28 Feb 2012, available online:
Luneva_WA_MAMM_submission.pdf - Accepted Version

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The geostrophic adjustment of a homogeneous fluid in a circular basin with idealized topography is addressed using a numerical ocean circulation model and analytical process models. When the basin is rotating uniformly, the adjustment takes place via excitation of boundary propagating waves and when topography is present, via topographic Rossby waves. In the numerically derived solution, the waves are damped because of bottom friction, and a quasi-steady geostrophically balanced state emerges that subsequently spins-down on a long time scale. On the f-plane, numerical quasi-steady state solutions are attained well before the system's mechanical energy is entirely dissipated by friction. It is demonstrated that the adjusted states emerging in a circular basin with a step escarpment or a top hat ridge, centred on a line of symmetry, are equivalent to that in a uniform depth semicircular basin, for a given initial condition. These quasi-steady solutions agree well with linear analytical solutions for the latter case in the inviscid limit. On the polar plane, the high latitude equivalent to the β-plane, no quasi-steady adjusted state emerges from the adjustment process. At intermediate time scales, after the fast Poincaré and Kelvin waves are damped by friction, the solutions take the form of steady-state adjusted solutions on the f-plane. At longer time scales, planetary waves control the flow evolution. An interesting property of planetary waves on a polar plane is a nearly zero eastward group velocity for the waves with a radial mode higher than two and the resulting formation of eddy-like small-scale barotropic structures that remain trapped near the western side of topographic features.

Item Type: Publication - Article
Digital Object Identifier (DOI):
Programmes: NOC Programmes
POL Programmes
ISSN: 0705-5900
Additional Keywords: geostrophic adjustment, polar circulation, Kelvin waves, vorticity waves
NORA Subject Terms: Marine Sciences
Date made live: 23 May 2012 10:57 +0 (UTC)

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