A coupled model simulation of Ocean thermohaline properties of the last glacial maximum

Abstract

The temperature and salinity of the ocean during the last glacial maximum (LGM) are simulated using a coupled ocean‐atmosphere‐sea‐ice climate model. The imposition of boundary conditions representitive of the LGM leads to deep ocean heat loss to the atmosphere in high latitude convection regions through active vertical mixing and associated turbulent heat fluxes with deepwater temperatures approaching the freezing point. The LGM conditions also modify the freshwater distribution at the ocean surface and cause a marked change in the ocean convection, overturning circulation, and ocean salinity distribution. In the LGM, the ocean becomes substantially fresher in the Atlantic basin due to a freshening of the northern North Atlantic and an associated reduction in North Atlantic Deep Water formation, while the most saline water mass is found in the Southern Ocean as a result of the increase in the formation of sea ice and the drier climate around Antarctica. The LGM thermohaline properties simulated by the coupled model are in reasonable agreement with palaeoclimatic proxy evidence.