UMR CNRS 5805 EPOC
Environnements et Paléoenvironnements
Océaniques et Continentaux

        

Consignes de Sécurité et Numéros d'Urgence
(à l'usage des personnels du laboratoire)

le 26-10-2012 à 11:00

Lieu Salle Stendhal, DGO, Bâtiment B18 Intervenant(s) Julie DESHAYES, Laboratoire de Physique des Oceans, LPO-CNRS

Abrupt climate changes in the past 20,000 years are, in part, explained by switches of the Meridional Overturning Circulation (hereafter MOC), associated with fluctuations in freshwater (hereafter FW) content in the North Atlantic. Climate models predict a freshening of high latitude North Atlantic that may induce an abrupt change of the MOC, if it resides in an unstable regime. The latter, which depends on salt advection feedback, remains uncertain as there is no consensus among observations, ocean reanalyses and climate models.
I will first come back to the impact of FW on the circulation in the North Atlantic. Inter-comparison of 4 state-of-the-art climate models underscores the large differences in their representations of the North Atlantic FW budget and impact on MOC. Second, I will use a series of four global 1/12◦ hindcast simulations of the last decades to diagnose FW transport by the MOC in the South Atlantic, an indicator of MOC stability. In all simulations, present-day MOC is unstable, which is opposite to what most climate models suggest. This advocates more inter-comparison studies of models of varying complexity in order to understand better the role of oceanic FW in MOC variability hence climate.