Late Quaternary moisture export across Central America and to Greenland: evidence for tropical rainfall variability from Costa Rican stalagmites |
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| Authors: | Matthew S Lachniet Leah Johnson Yemane Asmerom Stephen J Burns Victor Polyak William P Patterson Lindsay Burt April Azouz |
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| Institution: | 1. Department of Geography, University of Georgia, Athens, GA 30602, USA;2. Department of Geology, University of Georgia, Athens, GA 30602, USA;3. Department of Geography, Western Illinois University, Macomb, IL 61455, USA;4. Department of Anthropology, Trent University, Peterborough, ON, K9L 0G2, Canada;6. Bayer School of Natural and Environmental Sciences, Duquesne University, Pittsburgh, PA 15282, USA;7. College of Global Environmental Change, Xi''an Jiaotong University, Xi''an, Shaanxi 710049, PR China;8. Department of Geology and Geophysics, University of Minnesota, Minneapolis, MN 55455, USA |
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| Abstract: | We present a high-resolution terrestrial archive of Central American rainfall over the period 100–24 and 8.1–6.5 ka, based on δ18O time series from U-series dated stalagmites collected from a cave on the Pacific Coast of Costa Rica. Our results indicate substantial δ18O variability on millennial to orbital time scales that is interpreted to reflect rainfall variations over the cave site. Correlations with other paleoclimate proxy records suggest that the rainfall variations are forced by sea surface temperatures (SST) in the Atlantic and Pacific Oceans in a fashion analogous to the modern climate cycle. Higher rainfall is associated with periods of a warm tropical North Atlantic Ocean and large SST gradients between the Atlantic and Pacific Oceans. Rainfall variability is likely linked to the intensity and/or latitudinal position of the intertropical convergence zone (ITCZ). Periods of higher rainfall in Costa Rica are also associated with an enhanced sea surface salinity gradient on either side of the isthmus, suggesting greater freshwater export from the Atlantic Basin when the ITCZ is stronger and/or in a more northerly position. Further, wet periods in Central America coincide with high deuterium excess values in Greenland ice, suggesting a direct link between low latitude SSTs, tropical rainfall, and moisture delivery to Greenland. Our results indicate that a stronger tropical hydrological cycle during warm periods and large inter-ocean SST gradients enhanced the delivery of low latitude moisture to Greenland. |
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