Tropical Pacific Decadal Variability plays an important role in the global climate as evident from its influence on the recent slowdown of the globally-averaged surface temperature trend as well as its impacts on fisheries, onset of Spring over the western US, and other quantities relevant for society. A CLIVAR Tropical Pacific Decadal Variability Working Group (TPDV WG) was established by the CLIVAR Pacific Region Panel (PRP), with 28 participants that include both PRP members and other experts and early-career scientists from the broader scientific community. The motivation for the WG stems from the open questions identified by the PRP-led workshops and review paper on TPDV, which have highlighted the need to synthesize our state-of-knowledge on different mechanisms of TPDV involving ocean dynamics and assess their relative importance. The WG will also investigate the influence of inter-basin interactions on TPDV.

The CLIVAR TPDV WG was launched with its first telecon organised on 19 May 2021. During the telecon, an overview presentation entitled ‘Observations of Decadal Variability in the Pacific Subtropical Cells (STCs)’ was given by Dr. Mike McPhaden, ex officio member of the PRP, highlighting the main hypotheses and open questions on TPDV research. The discussion then focused on some specific open questions related to TPDV, including the role of the Low Latitude Western Boundary Currents in the mass balance of equatorial thermocline; the role of tropical vs. extratropical wind forcing; the relative contribution of the Northern and Southern Hemispheres’ influences on TPDV, and the simulation of the STCs in the CMIP3 climate models.

Work in this WG will be primarily conducted virtually through email exchanges and monthly conference calls. The WG will first systematically review the role of oceanic processes in the origin of decadal timescales prior to examining coupled ocean-atmosphere feedbacks, and atmospheric influences from regions outside the tropical Pacific. A proposal for a hybrid session on Pacific Decadal Variability, with emphasis on TPDV, has been prepared by the WG and submitted for the 2022 Ocean Sciences Meeting.