Millennial-scale Tropical Rainfall Variability From 100 to 20 ka: Testing Cross-Isthmian Water Vapor Transport and Feedbacks on Thermohaline Circulation

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This project investigates the utility of speleothems (i.e., cave deposits) as a means to develop climate proxy data that could help constrain terrestrial rainfall variability, on millennial time scales, with sufficient temporal resolution to evaluate a possible tropical feedback mechanism related to oceanic thermohaline circulation. The general science goals are to constrain the tropical hydrological cycle through evaluation of rainfall amount as a proxy for cross-isthmian water vapor transport, as well as document tropical climate variability over the last 100,000 years.Specifically, the research team will work to generate high resolution (decadal to multidecadal) oxygen isotope time series, a proxy for tropical rainfall amount, from Uranium series dated stalagmites from Costa Rica and Mexico, sites that are currently under the influence of the Intertropical Convergence Zone (ITCZ). The guiding scientific hypothesis is that tropical rainfall during the last glacial period is dominated by millennial-scale Dansgaard/Oeschger (D/O) variability, which is forced by thermohaline circulation variability and sea surface temperatures in the tropical Atlantic Ocean. The researchers also hypothesize that Heinrich events are associated with deficient rainfall over Central America resulting from a southward displacement of the ITCZ.