Accueil > Actualités > Séminaires > Séminaire de Bunmei Taguchi


Titre : Large-scale ocean-atmosphere interaction enhanced by oceanic frontal variability in the North Pacific
Nom du conférencier : Bunmei Taguchi
Son affiliation : Jamstec
Laboratoire organisateur : LOCEAN
Date et heure : 27-06-2014 11h00
Lieu : UPMC, LOCEAN, tour 45-55, 4e étage
Résumé :

In the North Pacific, western boundary current extensions (WBCs) exhibit large interannual-to-decadal variability, as the response of the ocean to basin-scale wind forcing tends to focus on narrow oceanic frontal zones such as Kuroshio Extention (KE) and subarctic front (SAF). Whether such WBC variability can have any up-scale effects on well-known basin-scale feature of North Pacific decadal variability (PDV) is an open question. Here we argue that the WBC variability, particularly the latitudinal shift of the SAF, has prominent basin-scale impacts both on the atmosphere and the ocean in the North Pacific. Namely, our analysis of historical observations and a long-term, ocean front-resolving coupled GCM simulation consistently suggest that decadal-scale SST anomalies induced by the SAF’s latitudinal shift can excite large-scale, deep atmospheric circulation anomalies similar to the Pacific–North American pattern during early winter, through the modulation of storm track activity and its feedback forcing. On the ocean side, the SAF is characterized by large gradients of upper ocean mean spiciness (temperature that is density-compensated with salinity). Thus, the shift of the SAF also generates distinct upper ocean temperature anomalies that are density-compensated with salinity and can be advected eastward by background mean flows. In our CGCM simulation, the oceanic spiciness anomalies thus generated and propagated lead to large decadal-scale variability of the upper ocean heat content in the WBC region. These results suggest that the WBC region in the North Pacific is a crossroad that bridges large-scale atmospheric circulation variations and upper-ocean heat content variability on decadal time scale. Better simulating the WBC variability in climate models may provide additional source of variability and predictability for PDV.