2023 NESSI Presentations - Nishchitha Etige

Watch 2023 NESSI intern Nishchitha Etige's end-of-summer presentation, "Influence of Large-scale Kuroshio Extension Variability on the Pacific Decadal Precession in the High-Resolution Version of the Community Earth System Model."

The large-scale variations of the meridional sea surface temperature gradient associated with the Kuroshio Extension (KE) set up a north-south dipole pressure pattern over the North Pacific Ocean. This dipole represents the north-south phase of the Pacific Decadal Precession (PDP), a quasi-decadal mode of climate variability in the North Pacific atmosphere. Further, these KE variations alter the jet over the North Pacific modifying the zonal propagation of stationary wave energy. As a result, a downstream pressure response is established, giving rise to the east-west phase of the PDP. Empirical and dynamic investigations on ocean and atmospheric reanalyses have revealed this causal link between KE and PDP. In present work, we explore the representation of these causal links in the high-resolution version of the Community Earth System Model (CESM). By analyzing the model's piControl and historic (1878-2007) output, we obtained large-scale KE indices. The model successfully simulated the observed meridional SST gradient associated with KE's variability in both experiments. Consequently, it reproduced the PDP's dipole patterns over the North Pacific and the downstream atmosphere as observed in reanalysis. The presence of these KE and PDP causal links in the high-res CESM model will enable us to investigate the future of the KE and PDP relationship in a changing climate.