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| Titel |
Changing mid-latitude westerlies and their impact to Southern Ocean eddies in a coarse resolution ocean model. |
| VerfasserIn |
Matthias Hofmann, Miguel Angel Morales Maqueda |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250056513
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| Zusammenfassung |
| State-of-the-art models of the Earth’s climate system usually comprise - among other
components - coarse resolution non-eddy permitting ocean general circulation models
(OGCMs). Therein, the effects of baroclinic eddies are used to be highly parameterized
mainly following the concept by Gent and McWilliams (1990), where the bolus velocity is
calculated from the product of a constant Gent-McWilliams diffusivity (KGM) times the
gradient of the isopycnal slopes. In such models an intensification of the mid-latitude
westerlies over the Southern Ocean (SO) leads to a steepening of the slopes of the isopycnals
and a strengthening of the Antarctic Circumpolar Current (ACC) and the Atlantic meridional
overturning circulation (AMOC) in association with a more vigorous northbound Ekman
flux. However, recent simulations employing eddy resolving OGCMs reveal an accelerated
increase of the southward eddy transport when amplifying the SO mid-latitude
westerlies, which nearly entirely compensate the enhanced Ekman flux. As a result, the
increase in the strength of the ACC and the AMOC is considerably smaller in eddy
resolving than in non-eddy resolving models when subjected to elevated SO wind
stresses.
Here we present simulations employing a coarse resolution OGCM on base of
MOM-3 incorporating an eddy parameterization in which eddy compensation is
considerably enhanced by the use of a non-constant spatially varying value of KGM. We
will show, that parameterized effective diffusivities KGM attain maximum values
comparable to those derived from eddy resolving simulations. Although the degree of
eddy compensations under changing SO mid-latitude westerlies remains below
the level as suggested by eddy resolving models and observations, our approach
permits a more physical representation of the effects of eddies in non-eddy resolving
OGCMs. |
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