Vendredi 9 février à 11h, salle de séminaires IRPHE
Abstract: The Greenland ice cores that recorded the abrupt Northern Hemispheric climate variations of the past 100 kiloyears bear witness to one of the most exciting periods of Earth's recent climate history. These millennial-scale Dansgaard-Oeschger (D--O) cycles are characterized by an oscillation between relatively warm interstadial periods and cold stadial periods. Most theories that have been proposed to explain the DO cycles suggest an interplay between the Meridional Overturning Circulation (MOC), the ice sheets/shelves, and sea ice cover, but the exact combination of these physical mechanisms is still debated.
Here, we use recent progress in our theoretical understanding of the MOC to develop a simple predictive framework that captures the main characteristics of the DO cycles using a minimal number of physical variables. The theoretical model predicts that global atmospheric temperature and salinity fluxes control the relative length of stadial vs interstadial conditions. The robustness of the framework is tested against equilibrium solutions of a 3D ocean General Circulation Model.
The results suggest that the prominent Northern Hemisphere climate variability recorded in the Greenland ice cores is governed directly by the gradual evolution of global temperatures and can be explained by a relatively simple physical mechanism that involves coupled ocean--sea-ice dynamics.
Louis-Philippe Nadeau / ISMER (UQAR), Université du Québec, Canada