Glacial ocean circulation and property changes in the North Pacific

Abstract

The glacial water properties and circulation changes in the North Pacific Ocean are investigated using a coupled ocean-atmosphere-sea-ice climate model. With glacial boundary conditions, an increase in potential density in the upper layers of the northern North Pacific makes the water column highly unstable and eventually results in the enhancement of North Pacific Intermediate Water (NPIW) production, consistent with proxy evidence. The NPIW outflow reaches deeper layers than in the present-day ocean, but remains largely confined to the North Pacific. The increase in potential density is predominantly caused by the increase in salinity and, to a lesser extent, by decreases in temperature. The increase in surface salinity is especially high in the Sea of Okhotsk and the western Bering Sea, which are possible source areas of glacial NPIW production. In these regions, an increase in brine release due to a marked increase in sea ice, evaporation exceeding precipitation, and a reduction in river discharge contribute to the increase in surface salinity. In short a reduction in freshwater input to the northern North Pacific is the main reason for the increase in the production and outflow of glacial NPIW.