Task 1.3: Use inverse methods to make a physically consistent map of climate and circulation of the North Atlantic/Arctic during a chosen stadial and insterstadial state of the last glacial.
Ocean surface data as derived from the marine proxies will be used as input to an inverse model in order to optimize the physical circulation and sea ice conditions during two time periods of Marine Isotope Stage (MIS) 3: one representing cold stadial conditions with extensive Arctic sea ice cover; and one representing warm interstadial conditions with reduced sea ice. We will use is the adjoint version of the MITgcm and produce two state estimates, which is consistent with both the instrumental data and the physical laws as represented by the climate model. The surface fields from the adjoint ocean model will be used as input to stand-alone atmosphere GCM experiments where the signature of the atmospheric circulation (temperature, precipitation and isotopic composition) will be evaluated against Greenland ice cores and other terrestrial proxies. This evaluation will guide further refinements to North Atlantic and Arctic Ocean surface conditions in an iterative fashion, using the ocean adjoint model and the AGCMs to produce consistent sea ice cover and SST patterns for the time slices.