Accueil > Actualités > Séminaires > Séminaire d'Alexey Fedorov


Titre : The Pacific meridional overturning circulation (PMOC) in past warm climates
Nom du conférencier : Alexey Fedorov
Son affiliation : Yale university
Laboratoire organisateur : LOCEAN
Date et heure : 13-07-2016 11h00
Lieu : UPMC - 4 place Jussieu - Paris 5e - LOCEAN, tour 45/55, 4eme étage - salle de réunion
Résumé :

The Atlantic meridional overturning circulation (AMOC), which involves deep water formation in northern high latitudes, is a critical element of modern ocean circulation and climate. For the warm Pliocene, 4 to 3 million years ago, we present complementary measurements and modeling evidence of a comparable meridional overturning circulation cell in the Pacific (PMOC), indicating a dramatically different Atlantic/Pacific “double conveyor”. In particular, in Pliocene Subarctic Pacific ocean sediments, calcium carbonate accumulation rivaled that of the modern North Atlantic. Together with high accumulation rates of biogenic opal during that time this requires vigorous bi-directional communication between surface waters and the waters overlying the deep seafloor in the North Pacific, implying deep convection. Other data provide additional evidence of higher deep ocean oxygen concentrations. A Pliocene-like climate simulation reproduces this deep water formation, generating two co-occurring, Atlantic and Pacific overturning cells of comparable strength. The PMOC emerges as a result of the less intense hydrological cycle under warm conditions leading to the erosion of the subarctic halocline in the North Pacific (that prevents deep convection in the modern Pacific).