Transport, Heat, and Freshwater Fluxes within a Diagnostic Numerical Model (FRAM)

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  • 1 Institute of Oceanographic Sciences, Godalming, Surrey, United Kingdom
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Abstract

Results are presented from the integration of a fine-resolution numerical model of the ocean operating in a diagnostic mode. The region covered lies south of 24°S, as depicted in the FRAM Atlas. Here transports, heat, salt, and freshwater fluxes are examined at 60°S and near 30°S in all three oceans. Results are found to be generally realistic.

At midlatitude the meridional heat flux is largely determined by the structure of the mean meridional motions and to a lesser degree by the gyre-scale horizontal motions. These roles are reversed for freshwater fluxes. At a fixed high latitude the freshwater flux is determined by the mean meridional motions and the heat flux principally by the large-scale wandering of the circumpolar current across the latitude. Only in this latter case, namely for the heat flux at 60°S, do mesoscale motions contribute to a significant extent.

The model underestimates the production and export of abyssal water; the climatological state with which it is initialized is identified as the likely cause. A suggestion is offered for assessing the accuracy of diagnostic integrations.

Abstract

Results are presented from the integration of a fine-resolution numerical model of the ocean operating in a diagnostic mode. The region covered lies south of 24°S, as depicted in the FRAM Atlas. Here transports, heat, salt, and freshwater fluxes are examined at 60°S and near 30°S in all three oceans. Results are found to be generally realistic.

At midlatitude the meridional heat flux is largely determined by the structure of the mean meridional motions and to a lesser degree by the gyre-scale horizontal motions. These roles are reversed for freshwater fluxes. At a fixed high latitude the freshwater flux is determined by the mean meridional motions and the heat flux principally by the large-scale wandering of the circumpolar current across the latitude. Only in this latter case, namely for the heat flux at 60°S, do mesoscale motions contribute to a significant extent.

The model underestimates the production and export of abyssal water; the climatological state with which it is initialized is identified as the likely cause. A suggestion is offered for assessing the accuracy of diagnostic integrations.

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