Abstract

Many periods of Abrupt Climate change during the last deglaciation begin with a catastrophic meltwater flood to the North Atlantic (e.g. Younger Dryas, 8.2-kyr-event). Yet, there appears to be no obvious connection between the volume of meltwater released to the ocean and the severity or duration of the cooling that followed. Here I present results from a series of very high-resolution numerical ocean model simulations to show that the geographical source of the meltwater plays a key role in the overall response of the AMOC to freshwater forcing. I will initially look at an ‘8.2-kyr’ simulation and show – somewhat contrary to the ‘classic’ idea that meltwater covered the subpolar North Atlantic with freshwater – that meltwater might have been transported to the subtropical North Atlantic. In a second experiment I use the same high-resolution model to try and figure out whether an Arctic (Mackenzie River) or Eastern (St. Lawrence River) freshwater route to the ocean triggered the Younger Dryas cold episode ~13,000 years ago. I conclude by discussing some of the ‘pros’ and ‘cons’ of using high-resolution models to study these events, and also discuss my ongoing research looking at the transport of icebergs into the subtropics during Heinrich Events.

For more information see: http://www.pnas.org/content/109/49/19928.full.pdf+html