Talk by Francesco Muschitiello – Københavns Universitet

Talk by Francesco Muschitiello

(Lamont-Doherty Earth Observatory of Columbia University)

Title: "Deep-water circulation leads North Atlantic climate during the last deglaciation".

Abstract: Constraining the response time of the climate system to changes in Atlantic Meridional Overturning Circulation (AMOC) is fundamental to improve climate predictability. Here we present a precise synchronization of terrestrial, marine and ice-core records that reveals for the first time the ocean-atmosphere lead-lag nature during rapid North Atlantic climate transitions of the last deglaciation. Using a continuous record of deep water ventilation from the Nordic Seas, we identify a systematic ~250-year lead of deep-water export on abrupt climate changes recorded in Greenland ice cores –in and out of the Younger Dyas stadial (YD)– in response to gradual changes in freshwater forcing. Supported by transient climate model simulations, our results also point at a delayed response of atmospheric CO2 rise to AMOC slowdown at the onset of the YD. We conclude that variations in North Atlantic deep-water formation are precursors to large-scale climate and pCO2 changes, which highlights the need for improved long-term future AMOC projections.