Sensitivity of simulated salinities in a three-dimensional ocean general circulation model to vertical mixing of destabilizing surface fluxes |
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Authors: | P B Duffy K G Caldeira |
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Institution: | (1) Climate System Modeling Group, Lawrence Livermore National Laboratory, L-103, P.O. Box 808, Livermore, CA 94550, USA E-mail: pduffy@llnl.gov, US |
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Abstract: | We present simulations performed with a three dimensional global ocean general circulation model which show that simulated
salinities and amounts of convective mixing are very sensitive to vertical mixing of surface buoyancy fluxes. If, as usual,
surface buoyancy fluxes are placed entirely in the topmost model level, our model produces excessive convective mixing in
the Southern Ocean. This results in poor stimulated salinity in the Southern Ocean. In this simulation, we assume, as usual,
that both surface buoyancy forcing and vertical mixing are homogeneous within each grid cell. If, on the other hand, destabilizing
surface fluxes are instantaneously mixed into the subsurface ocean, the model produces much less convective mixing and much
more realistic salinities. The vertical mixing of surface buoyancy fluxes performed in this simulation is equivalent to assuming
that those fluxes affect only a small fraction of each grid cell, and cause vertical mixing only in that limited area. Our
interpretation of these results is that the usual assumption that both surface buoyancy forcing and vertical mixing are uniform
within each grid cell has a detrimental effect on model results; these results could be significantly improved by good parametrizations
which treat the horizontal inhomogeneity of surface buoyancy forcing and of vertical mixing.
Received: 25 February 1998 / Accepted: 9 September 1998 |
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