Application of Ocean Models for the Interpretation of Atmospheric General Circulation Model Experiments on the Climate of the Last Glacial Maximum

We examined the response of our ocean models of physical circulation and geochemical tracer distributions on atmospheric glacial forcing. The CLIMAP Project Members (1981) sea surface temperature (SST) was taken directly as a boundary condition. The wind stress and freshwater flux were derived from the ice age response of an atmospheric general circulation model (AGCM). Near the surface, the ocean response in temperature and circulation reflects primarily the imposed glacial forcing fields. The simulated deep ocean response, especially in the North Pacific, is in conflict with the observational evidence. The glacial changes in the physical ocean circulation appear to be qualitatively as derived from sediment cores, but, probably, highly overestimated. The misfit between model and data is established clearly in the distribution of δ 13 C, where a direct comparison with sediment core data is possible. The simulated AGCM freshwater flux, which is linked for example by the evaporation to the imposed SST field, is suspected to be the most probable reason for this conflict.