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| Titel |
Contribution of eddies to the salt transport in the global ocean as revealed by DRAKKAR eddy-resolving simulations |
| VerfasserIn |
Anne Marie Treguier, Julie Deshayes, Thierry Penduff, Claude Talandier |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250078583
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| Zusammenfassung |
| The spatial distribution of salinity in the world ocean is governed by the ocean circulation
that transports salt from evaporative subtropical regions to precipitation-dominated regions
(at high latitudes and in the tropics). Observations suggest that in a steady state, up to 30. 106
kg/s of salt must be carried by circulation cells with correlated velocities and salinities,
in order to compensate for the effect of surface forcings. This transport is both
advective and diffusive, the diffusive component being mainly due to mesoscale
eddies that are the most energetic agents of lateral mixing at the scale of ocean
basins; however this eddy-driven transport cannot be quantified from observations
alone.
A suite of global simulations at 1/12° resolution using the NEMO-based ORCA12 model
have been performed by the DRAKKAR group. These simulations allow to calculate
precisely the eddy contribution to salt transports resulting from the correlation between
fluctuating velocities and salinities. At mid latitudes, 40°S and 40°N, the eddy salt transport
reaches almost -10. 106 kg/s and 10. 106 kg/s respectively. This contribution almost as large
as the transport by the mean circulation cells at 40°S and 40°N. The latitudinal structure of
eddy salt transport agrees qualitatively with estimates from observations based on the
hypothesis that mesoscale eddies diffuse high salinity anomalies away from the saline
subtropical regions.
Sensitivity experiments demonstrate the robustness of these estimates with respect to
atmospheric forcing datasets and numerical parameters, even though these differences
between the simulations lead to significant modifications of the eddy distribution and western
boundary current characteristics. The comparison with a global eddy-permitting simulation at
1/4° allows us to assess the dependency of the eddy fluxes on model resolution and on
subgrid-scale parameterizations. Our calculation of eddy contribution to salt transport
at the global scale demonstrates that eddies are likely to play a major role in the
redistribution of salinity that is presently occuring due to anthropogenic climate
change. |
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