Wave-induced abyssal recirculations

Spall, Michael A. (1994) Wave-induced abyssal recirculations Journal of Marine Research, 52 (6). pp. 1051-1080. DOI 10.1357/0022240943076830.

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The forcing of abyssal recirculation gyres by cross-isopycnal mixing and wave fluxes near the deep western boundary is investigated. A three-layer isopycnal primitive equation model is applied in a series of experiments to an idealized basin with bottom topography. In the absence of deep western boundary current instabilities, cross-isopycnal mixing forces a cyclonic recirculation gyre, modified by topography, which is consistent with the traditional Stommel-Arons model. Instabilities of the boundary current fundamentally alter the mean basin-scale deep flow from a cyclonic recirculation to an anticyclonic recirculation. Bottom topography plays a key role in destabilizing the mean flow. The forcing mechanism for the interior recirculation is the horizontal divergence of momentum and potential vorticity fluxes carried by topographic waves that are forced by the boundary current instabilities. The strength of the recirculation gyre is linearly proportional to the kinetic energy of the waves, which is controlled in the present model by bottom drag, and well predicted by a simple scale analysis. This is essentially an adiabatic process. The addition of cross-isopycnal mixing forces the large-scale interior recirculation toward the pole, partially into boundary currents, through linear vorticity dynamics. Vorticity budgets reveal three dynamical regimes for the eddy-driven flows, the western boundary current, the recirculation region, and the interior. Similarities and differences between the mean flow and recent observations in the Brazil Basin are discussed.

Document Type: Article
Research affiliation: OceanRep > Institute for Marine Science Kiel
Refereed: Yes
DOI etc.: 10.1357/0022240943076830
ISSN: 0022-2402
Date Deposited: 15 Jun 2018 09:09
Last Modified: 15 Jun 2018 09:10
URI: http://eprints.uni-kiel.de/id/eprint/43407

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