Dynamics of contrasting pattern formation of thermocline and mixed layer temperature in the Pacific Ocean across interannual, decadal and climate change timescales

Columbia University, New York NY

Investigators

Abstract

The Pacific Ocean is a key region for coupled atmosphere-ocean phenomena that influence global climate across different timescales. Currently, seasonal-to-interannual climate predictions predominantly rely on forecasting El Niño-Southern Oscillation (ENSO) while there are emerging efforts on Pacific-rim decadal predictions based on forecasting phases of Pacific Decadal Variability (PDV). In turn global climate change projections hinge on predicting forced changes in the tropical Pacific. On this, however, there is substantial disagreement between models which favor a reduced zonal sea surface temperature gradient and observations which show an increase. The discrepancy reduces confidence in models’ future projections; the differences are critical for associated regional climate change, tropical cyclone behavior and climate sensitivity. By integrating observational analyses, theoretical demonstrations, and model experiments, this research will significantly advance our fundamental understanding of key aspects of Pacific dynamics. The gained understanding is essential for reconciling why climate models struggle to simulate historical trends in the tropical Pacific Ocean and how the models can be improved so as to provide more reliable and accurate predictions and projections of regional climate change and the rate of global warming. The lead investigator is an early career researcher and this work will advance her career focused on the ocean’s role in climate variability and change. This project aims to explain why the patterns of thermocline depth and mixed layer temperature change are meridionally broader for PDV than interannual ENSO and why the climate change patterns are again more meridionally confined and generally distinct from those of PDV. In this context, the research aims to comprehensively investigate the dynamics of contrasting pattern formation of thermocline and mixed layer temperature in the Pacific Ocean across interannual, decadal, and climate change timescales by understanding the different ocean dynamics, surface heat flux and cloud-radiation-sea surface temperature feedbacks involved. Of particular interest is to determine why the climate change signal does not amplify via Bjerknes feedbacks into a pattern more akin to ENSO or PDV and, instead, remains stable. In addition, the study will quantify the connections across timescales of the tropical Pacific Ocean and the Southern Ocean and determine the role of the latter in influencing the climate change pattern in the tropics. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.