Collaborative Research: Characterizing Northern Hemisphere Atmospheric Variability from Central American Wind Gap-Induced Upwelling

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There are three locations along the Central American Sierra Madre mountains that are low enough to allow winds to pass from the Atlantic to the Pacific Ocean. The northernmost of these wind gaps is the ‘Tehuantepec Gap’ (along the southwest coast of Mexico). These locally known winds (here simply Tehuantepec Gap Winds) drive intense upwelling of cool, nutrient-rich water in the Gulf primarily in the winter when high atmospheric pressures over North America establish a pressure gradient across the Isthmus of Tehuantepec. Despite the potential importance of the Tehuantepec Gap Winds as an Atlantic-Pacific teleconnection, there has been no attempt to predict the response of these winds to changes in regional climate dynamics in the context of rapid and global climate change. The researchers suggest to combine past climate records of upwelling (from sedimentary radiocarbon over the last 30.000 years) and model simulations to characterize atmospheric dynamical processes over the North Atlantic, and to examine both the sensitivity of these winds to ‘upstream’ factors as well as the ‘downstream’ implications of this inter-basin coupling. A novel Atlantic-Pacific Ocean-atmosphere feedback mechanism is suggesting in the methodological framework and hypothesis testing of this project in which the Tehuantepec Gap Winds and atmospheric Rossby waves play a central role. This collaborative project will support two early career scientists, and the education and scientific training of undergraduate students at UC Irvine (both a Hispanic Serving Institution and Native American Pacific Islander-Serving Institution). The researchers will continue engagement in their institution’ broadening participation efforts, including ATOC REU in Atmospheric, Oceanic, and Cryospheric Sciences (NSF 2150262), a program that primarily recruits from Hispanic Serving Institutions to introduce students to data science and geoscience research. Additionally, a lesson plan focused on long-term variations in Earth’s climate will be developed as part of this project and piloted through Environmental Climate Change and Literacy Projects in California’s outreach programs and posted in an openly available national online repository for climate pedagogy (called “Subject to Climate”).The Gulf of Tehuantepec is an ideal location to characterize ‘upstream’ atmospheric processes linking the Pacific and Atlantic sectors because a prominent gap in the Sierra Madre mountains forces low-level winds to flow through the Isthmus of Tehuantepec toward the Pacific, driving local upwelling of deeper, lower radiocarbon waters to the surface. A preliminary model results and sediment core measurements leverage this wind-to-radiocarbon relationship to provide a precious constraint on Northern Hemisphere atmospheric dynamics over the past 23,000-years. Previous studies of contemporary climate variability and preliminary examinations of models and observational products indicate that higher atmospheric pressure over North America is associated with high near-surface pressure in the Gulf of Mexico, leading to stronger Tehuantepec winds. The project suggested here—including new sediment proxy measurements, model (Paleoclimate GCM) and data product examinations, and forward modeling—aims to discover the driving mechanisms behind the variability in Tehuantepec gap wind strength over paleoclimate timescales, which will provide a crucial new constraint on glacial-interglacial atmospheric dynamics in addition to controls on tropical Pacific Sea Surface Temperature and inter-basin moisture fluxes.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.