[A-CG31] Climate Variability and Predictability on Subseasonal to Centennial Timescales

[ACG31-P04] Heat budget in the surface layer related to the Pacific Decadal Oscillation

*Satoshi Osafune¹, Shinya Kouketsu¹ (1.Japan Agency for Marine-Earth Science and Technology)

Keywords:PDO, heat content, geostrophic current, multi-decadal variability

The Pacific Decadal Oscillation (PDO) is a dominant year-round pattern of monthly North Pacific sea surface temperature (SST), and is often used as a key time-series to understand various variations in ocean and climate. As a result of numerous studies on PDO to date, a consensus is forming that the PDO is not a single physical mode but caused by a combination of different processes, which includes not only local forcings but also ocean gyre dynamics. To better understand the PDO, it is necessary to quantitatively compare the impacts of each process and to understand the mechanisms driving ocean circulation variability that affect the PDO. In this study, we focus on the heat content in the center of action of the PDO, and investigate its budget using an ocean state estimation, ESTOC, in which heat budget is closed. Our result indicates that the convergence of heat transport by the geostrophic current cannot be ignored to reproduce the multi-decadal variation of the heat content, while the local forcing, the sum of surface heat flux and Ekman transport largely explain short-period (within a few years) variation. We will summarize the periodicity of each process and discuss their roles and mechanisms.