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The Impact of Small-Scale Topography on the Dynamical Balance of the Ocean

The Impact of Small-Scale Topography on the Dynamical Balance of the Ocean
The Impact of Small-Scale Topography on the Dynamical Balance of the Ocean
The impact of small-scale topography on the ocean’s dynamical balance is investigated by quantifying the rates at which internal wave drag extracts (angular) momentum and vorticity from the general circulation. The calculation exploits the recent advent of two near-global descriptions of topographic roughness on horizontal scales on the order of 1–10 km, which play a central role in the generation of internal lee waves by geostrophic flows impinging on topography and have been hitherto unresolved by bathymetric datasets and ocean general circulation models alike. It is found that, while internal wave drag is a minor contributor to the ocean’s dynamical balance over much of the globe, it is a significant player in the dynamics of extensive areas of the ocean, most notably the Antarctic Circumpolar Current and several regions of enhanced small-scale topographic variance in the equatorial and Southern Hemisphere oceans. There, the contribution of internal wave drag to the ocean’s (angular) momentum and vorticity balances is generally on the order of ten to a few tens of percent of the dominant source and sink terms in each dynamical budget, which are respectively associated with wind forcing and form drag by topography with horizontal scales from 500 to 1000 km. It is thus suggested that the representation of internal wave drag in general circulation models may lead to significant changes in the deep ocean circulation of those regions. A theoretical scaling is derived that captures the basic dependence of internal wave drag on topographic roughness and near-bottom flow speed for most oceanographically relevant regimes.
0022-3670
647-668
Naveira Garabato, Alberto C.
97c0e923-f076-4b38-b89b-938e11cea7a6
Nurser, A.J. George
2493ef9a-21e9-4d8b-9c32-08677e7e145a
Scott, Robert B.
f82756a5-f04c-41f1-a6c8-12574b9814cf
Goff, John A.
3677617d-c1a0-4c27-b6e5-acb4e734e7f1
Naveira Garabato, Alberto C.
97c0e923-f076-4b38-b89b-938e11cea7a6
Nurser, A.J. George
2493ef9a-21e9-4d8b-9c32-08677e7e145a
Scott, Robert B.
f82756a5-f04c-41f1-a6c8-12574b9814cf
Goff, John A.
3677617d-c1a0-4c27-b6e5-acb4e734e7f1

Naveira Garabato, Alberto C., Nurser, A.J. George, Scott, Robert B. and Goff, John A. (2013) The Impact of Small-Scale Topography on the Dynamical Balance of the Ocean. Journal of Physical Oceanography, 43 (3), 647-668. (doi:10.1175/JPO-D-12-056.1).

Record type: Article

Abstract

The impact of small-scale topography on the ocean’s dynamical balance is investigated by quantifying the rates at which internal wave drag extracts (angular) momentum and vorticity from the general circulation. The calculation exploits the recent advent of two near-global descriptions of topographic roughness on horizontal scales on the order of 1–10 km, which play a central role in the generation of internal lee waves by geostrophic flows impinging on topography and have been hitherto unresolved by bathymetric datasets and ocean general circulation models alike. It is found that, while internal wave drag is a minor contributor to the ocean’s dynamical balance over much of the globe, it is a significant player in the dynamics of extensive areas of the ocean, most notably the Antarctic Circumpolar Current and several regions of enhanced small-scale topographic variance in the equatorial and Southern Hemisphere oceans. There, the contribution of internal wave drag to the ocean’s (angular) momentum and vorticity balances is generally on the order of ten to a few tens of percent of the dominant source and sink terms in each dynamical budget, which are respectively associated with wind forcing and form drag by topography with horizontal scales from 500 to 1000 km. It is thus suggested that the representation of internal wave drag in general circulation models may lead to significant changes in the deep ocean circulation of those regions. A theoretical scaling is derived that captures the basic dependence of internal wave drag on topographic roughness and near-bottom flow speed for most oceanographically relevant regimes.

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Published date: March 2013
Organisations: Marine Systems Modelling, Physical Oceanography

Identifiers

Local EPrints ID: 352263
URI: http://eprints.soton.ac.uk/id/eprint/352263
ISSN: 0022-3670
PURE UUID: d3452b51-9c2e-4155-80b3-f51c7761a35f
ORCID for Alberto C. Naveira Garabato: ORCID iD orcid.org/0000-0001-6071-605X

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Date deposited: 08 May 2013 10:41
Last modified: 15 Mar 2024 03:24

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Contributors

Author: A.J. George Nurser
Author: Robert B. Scott
Author: John A. Goff

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