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 glacial boundary conditions leads to deep ocean heat loss to the atmosphere at high latitude convection regions through an active vertical mixing and associated turbulent heat fluxes and deepwater temperature approaches to the freezing point. The LGM conditions also modify the fresh water 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 northern North Atlantic and associated reduction in North Atlantic Deep Water formation, while the saltiest water mass is found in the Southern Ocean as a result of the increase in the formation of sea ice and drier climate around Antarctica. The LGM thermohaline properties simulated by the coupled model are in reasonable agreement with paleoclimate proxy evidence.