P2C2:Collaborative Research: A Speleothem Study of the Paleoclimatology of the Yucatan Peninsula: Testing Modes and Causes of Variability in the North American Tropics

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This project's goal is to reconstruct low latitude precipitation variability, from interannual to orbital time scales, to better understand hydrological responses to meso and large-scale atmosphere and ocean dynamics, external forcing, and feedbacks in the Yucatan Peninsula (YP). The mechanisms proposed for driving suborbital scale climate regimes in the region include ENSO, tropical cyclogenesis and shifts in precipitation associated with movements of the Inter Tropical Convergence Zone (ITCZ), but available paleoclimate records are contradictory in terms of causal factors.The project could potentially improve rainfall sensitivity estimates that would represent an empirical assessment independent of models. Current international climate model estimates of precipitation changes in the region by the end of this century vary over a significant range (-50% to +9% relative to today). The project would also support an underrepresented minority early-career scientist and provide an early experience in research to several undergraduate students. In addition, the research team will produce educational materials and exhibits for a general audience in Spanish and English language versions.The research team will use speleothems from caves of the YP to reconstruct the character of hydrological variability in the region during the Holocene, the last glacial interval, marine isotope stage (MIS) 5, and MIS 7 to 9. In particular, the team will make quantitative reconstructions of precipitation changes based on delta-18Oxygen isotopes in stalagmites. In combination with available lacustrine records from the YP, local speleothem records may provide a unique opportunity to quantitatively reconstruct the precipitation to evaporation balance in the region. Quantitative high-resolution Holocene and Late Pleistocene precipitation records will: 1) provide quantitative estimates of past rainfall variability; 2) test the relationship between rainfall variability and shifts in mean ITCZ; 3) investigate the role of ENSO, tropical sea surface temperatures and cyclones in driving climate regimes in the YP; and 4) provide estimates of the sensitivity of tropical hydrology.The researchers will leverage an active collaboration with the Rio Secreto Reserve, a commercial enterprise that leads ~50,000 tourists through a large, partially submerged cave system on the east coast of the YP for education and outreach aims. The cave system of Rio Secreto represents an ideal cave system for reconstructing precipitation changes from stalagmites in the region extending approximately 300,000 years before the present.