Simulations of two last glacial maximum ocean states

Abstract

Two stable thermohaline circulation states were produced in simulations of the last glacial maximum (LGM) ocean, both forced by the same prescribed atmosphere. Direct application of this atmosphere led to an equilibrium state with strong North Atlantic Deep Water formation (northern sinking state (NSS)). Upon applying a weak freshwater flux anomaly to the North Atlantic for a short time a state was entered with little North Atlantic, but significant Southern Ocean, Deep Water formation (southern sinking state (SSS)). A fully dynamic and thermodynamic iceberg trajectory model was developed, and icebergs were seeded into both states. Distinctly different pathways were found, particularly in the eastern Atlantic where the SSS icebergs tend to move south along the European coast while they move north in the NSS. While neither ocean state is claimed to be a definitive model for the LGM ocean, paleoclimate data are more consistent with the characteristics of the NSS.