[A-CG33] Multi-scale ocean-atmosphere interaction in the tropics

[ACG33-10] Long-term variability of the Pacific shallow overturning circulation reproduced by the OFES2 hindcast simulation

*Takeshi Anami¹, Yukio Masumoto¹ (1.The University of Tokyo)

Keywords:Subtropical Cells, Tropical Pacific Decadal Variability

The decadal to interdecadal climate variability in the tropical Pacific, often referred to as Tropical Pacific Decadal Variability (TPDV), is known to have significant impacts on climate modes around the world and identifying their underlying mechanisms is crucial for better understanding and prediction of TPDV. It is believed that such decadal variability in ocean heat content anomaly can be modulated by the changes of the heat transport from the subtropics to the tropics through shallow meridional overturning circulation called the Subtropical Cells (STC). Two scenarios have been suggested to explain the heat transport anomaly by the STC; (i) anomalous temperature transported by mean circulation and (ii) mean temperature transported by anomalous circulation. However, the relative importance between the two scenarios and temporal modulation of this relation are still under debate.
In this study, we investigate the spatiotemporal long-term variations of the STC in the Pacific using results from a high-resolution OGCM, OFES2, driven by atmospheric forcing (JRA55-do) for the years 1958-2016. The OFES2 results reproduce the decadal variations in the tropical Pacific and the STC reasonably well. The variations of meridional heat transport across the section at 10º latitude in the northern and southern hemisphere are analyzed. The analysis indicates that the contribution of scenario (ii) is dominant throughout the whole period, whereas scenario (i) showed significant contribution in certain periods (1970s and 1990s).