Influence of the freshwater forcing pathway on the AMOC during 8.2k event

Abstract:

The collapse of the proglacial lakes Agassiz and Ojibway and the discharge of the lake water into the Hudson Bay were identified as the cause of the cold event occurred around 8.2 thousand years before present day (8.2kybp). This event has been widely studied using coupled climate models by adding freshwater forcing into the subpolar North Atlantic. However, results from the coarse resolution coupled models differ from that of a high resolution forced standalone ocean model simulation. Here we use a state-of-art fully coupled high-resolution climate model with 1/10 degree horizontal resolution for the ocean and sea ice, and ¼ degree for the atmosphere and land components to study the influence of the freshwater forcing to the Atlantic Meridional Overturning Circulation (AMOC). In this simulation, 2 Sv freshwater is added into the North Atlantic along a narrow band of west Baffin Bay to North of Labrador Sea for two years, then the freshwater forcing is switched off. Our preliminary results show that AMOC weakens by over 30% within the first 10 years, and recovers afterwards. The added freshwater were partly transported into the subpolar North Atlantic and partly into the subtropical gyre. The latter part was carried by Gulf Stream into the subpolar North Atlantic about 25 years later.