ABSTRACT FROM:Sensitivity of sea ice to physical parameterizations in the GISS global climate model
Journal of Geophysical Research - Oceans, accepted pending revisions
The GISS coupled model is used to investigate the sensitivity of sea ice to each of the following parameterizations: a) two sea ice dynamic schemes (CF: cavitating fluid and VP: viscous-plastic), b) the specification of the oceanic isopycnal mixing coefficients in the Gent & Mcwillams isopyncal mixing scheme (GM) and c) Wajsowicz viscosity diffusion (WV). The large-scale sea ice properties are highly sensitive to sea ice dynamics. With the inclusion of the resistance to shear stress, the VP scheme captures the major observed sea ice drift features, and improves the simulations of sea ice concentrations, thickness and export through Fram Strait relative to the CF scheme. The GM scheme significantly improves the simulation of vertical temperature distributions in the Southern Ocean, although it leads to a dramatic reduction of Antarctic sea ice cover. A reduced oceanic isopycnal mixing coefficients (varying spatially and temporally) leads to Arctic sea ice that tends to be less and thinner in almost the entire Arctic except in the North Pacific and Labrador Sea, while Antarctic sea ice that extends more equatorward throughout the circumpolar regions. The response of sea ice to the WV scheme shows an enlargement and thickening of sea ice in the Arctic, within the ice packs around the Antarctic and a reduction and thinning of sea ice in the northern Weddell and Ross Seas. Based on these experiments, two composite experiments with the best parameterizations are investigated. The atmospheric responses associated with sea ice changes are discussed. While improvements are seen overall, there are still many unrealistic aspects that will require further improvements to the sea ice and ocean components.
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