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Vorticity Balance in the ECCO Global WOCE Synthesis |
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Y. Lu and D. Stammer for the ECCO Consortium. |
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From an ocean model that was constrained by WOCE data sets as |
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part of the NOPP-funded ECCO assimilation project, we analyze |
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the barotropic vorticity budget of the global ocean. |
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For the depth-integrated circulation, it is found that the |
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bottom pressure torque (BPT) dominates over the curl of friction |
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in the western boundary currents and in the Southern Ocean. |
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This important role played by BPT in the dynamics of the western |
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boundary currents and the Antarctic Circumpolar Current (ACC), |
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as found in this 2 degree-resolution simulation, is consistent |
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with the recent theoretical argument and the analyses of |
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eddy-resolving simulations. |
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In the upper layer of the model, the classical Sverdrup balance |
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holds only in the eastern sub-tropical basins. The vorticity |
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stretching/compressing associated with the vertical velocity |
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is important near western boundary currents and in at high latitudes. |
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In the intermediate layer, the vorticity stretching/compressing |
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associated with vertical motions drive the meridional flow |
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in the interior basins. |
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For the deep ocean, it is the combination of BPT and the vertical |
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velocity that balances the advection of planetary vorticity. |
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The meridional flow in the abyssal ocean is driven |
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by the combined effect of BPT and vertical motions. |
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The simulated abyssal circulation in the interior basins bears |
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little resemblance with the prediction of the Stommel-Arons theory. |
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