Transient response of the North Pacific to glacial boundary conditions

Abstract

The transient response of the North Pacific Ocean to glacial boundary conditions was investigated using the coupled atmosphere-ocean-sea ice model developed at Canadian Centre for Climate Modelling and Analysis (CCCma). With the implementation of the glacial boundary conditions, the global-mean sea surface temperature (SST) decreases rather substantially and the surface cooling is larger for the first several decades by about 1.5 °C with in 10 years, 2 °C within 20 years, and by about 3°C within 80 years. Sea surface salinity also decreases with glacial conditions for the first decade, but it persists with that level with time. The North Atlantic overturning circulation increases markedly at the beginning of the perturbation by more than 40 Sv. In response to the glacial boundary conditions, sea surface salinity (SSS) markedly reduced by more than 1.5 psu with in 10 years in the East/Japan Sea associated with the limitation of salty water influx, which is a branch of the Kuroshio warm current. SSS is also reduced in the Okhotsk Sea, the Bering Sea, and the tropical Pacific, whereas it increases in the North and Southwest Pacific. With time, the freshening along the mid latitudes is becoming stronger and the low salinity feature in the tropical Pacific found in the first decade is changed into high salinity tongue. In the northeastern Okhotsk Sea and the northwestern margin of the Bering Sea SSS increases with time. In conclusion, with the implementation of glacial boundary conditions, the most distinctive change is found over the East/Japan Sea where SST and SSS are markedly reduced. This change is associated with the limitation of warm water influx to those regions due to the sea level lowering by about 120 m in the glacial time. The marked change in the East/Japan Sea subsequently influences the North Pacific ocean properties.