Oceanic processes as potential trigger and amplifying mechanisms for Heinrich events

Marine sediments recorded a series of Heinrich events during the last glacial period, massive ice surges that deposited prominent layers of ice-rafted debris in the North Atlantic. Here we explore oceanic mechanisms that can potentially trigger and amplify the observed ice calving events. Simulations of abrupt glacial climate change with a coupled ocean-atmosphere- sea ice model show a substantial regional sea level rise in the North Atlantic in response to a collapse of the Atlantic meridional overturning circulation (MOC). The increased heat uptake of the global ocean after the MOC collapse leads to an additional rise in global sea level. We hypothesize that these sea level changes have the potential to destabilize Northern Hemisphere ice shelves and ice sheets and to trigger ice surges. Sea level rise due to ice calving and subsurface ocean warming provides two positive feedback mechanisms contributing to further destabilization of ice shelves and ice sheets.