HR: 10:35h
AN: PP52A-02    [Abstracts]
TI: Central American Rainfall Variations Over the Past 100,000 yr From Costa Rican Stalagmites: a Proxy for Cross-Isthmian Water Vapor Transport
AU: * Lachniet, M S
EM: matthew.lachniet@unlv.edu
AF: Department of Geoscience, University if Nevada, Las Vegas, Las Vegas, NV 89154, United States
AU: Asmerom, Y
EM: asmerom@unm.edu
AF: Department of Earth and Planetary Science, University of New Mexico, Albuquerque, NM 87131, United States
AB: We present results of oxygen isotope time series of several uranium-series dated stalagmites from Costa Rica that document decadal to multi-millennial scale variability in rainfall within the Intertropical Convergence Zone. Stalagmite samples recovered from caves along the Pacific Coast of Costa Rica largely reflect rainfall amount and moisture source on the Isthmus of Panama, and are direct proxies of the flux of moisture from the Caribbean to the Pacific Ocean. Such cross-isthmian transport is a key process involved in the thermohaline circulation of the North Atlantic Ocean and thus provides a direct link between low and high latitudes during the last glacial cycle. Our results indicate that Central American rainfall varied considerably over the past 100 ka, although our records do not cover marine isotope stage two. Rainfall was at a minimum at ca. 60 ka, with several rainfall maxima between 65-100 ka, at ca. 37 ka, and to a lesser extent during the Holocene. The data do not reveal any clear precessional insolation forcing of the Central American Monsoon. Rather, our data suggest an inverse correlation of Costa Rican rainfall with Galapagos sea surface temperatures, and wetter conditions associated with decreased salinity in the eastern equatorial Pacific Ocean.
DE: 1041 Stable isotope geochemistry (0454, 4870)
DE: 1620 Climate dynamics (0429, 3309)
DE: 1854 Precipitation (3354)
DE: 4958 Speleothems
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Joint Assembly