Effects of sinking of salt rejected during formation of sea ice on results of an ocean‐atmosphere‐sea ice climate model

Abstract
We show that results of an ocean‐atmosphere‐sea‐ice model are sensitive to the treatment of salt rejected during formation of sea ice. In our Control simulation, we place all rejected salt in the top ocean‐model level. In the Plume simulation, we instantaneously mix rejected salt into the subsurface ocean, to a maximum depth which depends on local density gradients. This mimics the effects of subgrid‐scale convection of rejected salt. The results of the Plume simulation are more realistic than those of the Control simulation: the spatial pattern of simulated salinities (especially in the Southern Ocean), deep‐ocean temperatures, simulated sea‐ice extents and surface air temperatures all agree better with observations. A similar pair of simulations using horizontal tracer diffusion instead of the Gent‐McWilliams eddy parameterization show similar changes due to instantaneous mixing of rejected salt.

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