HR: 10:35h
AN: U22B-02    [Abstracts]
TI: Central American rainfall variations since 100 ka and moisture delivery to Greenland
AU: * Lachniet, M S
EM: matthew.lachniet@unlv.edu
AF: University of Nevada, Las Vegas, Department of Geoscience Box 4010, Las Vegas, NV 89128, United States
AU: Asmerom, Y
EM: asmerom@unm.edu
AF: University of New Mexico, Department of Earth and Planetary Sciences MSC03-2040, Albuquerque, NM 87131, United States
AU: Johnson, L
EM: lrj80@unm.edu
AF: University of New Mexico, Department of Earth and Planetary Sciences MSC03-2040, Albuquerque, NM 87131, United States
AU: Burns, S
EM: sburns@geo.umass.edu
AF: University of Massachusetts, Amherst, Department of Geosciences 611 North Pleasant St 233 Morrill Science Center, Amherst, MA 01003, United States
AU: Polyak, V
EM: polyak@unm.edu
AF: University of New Mexico, Department of Earth and Planetary Sciences MSC03-2040, Albuquerque, NM 87131, United States
AU: Polyak, V
EM: polyak@unm.edu
AF: University of Saskatchewan, Department of Geological Sciences 114 Science Place, Saskatoon, SK S7N 5E2, Canada
AU: Patterson, W
EM: Bill.Patterson@usask.ca
AF: University of Saskatchewan, Department of Geological Sciences 114 Science Place, Saskatoon, SK S7N 5E2, Canada
AB: We present a rainfall history for Central America based on oxygen isotope values in Uranium-series dated stalagmites collected from the Pacific Coast of Costa Rica over parts of the Holocene and from 25 to 100 ka. The oxygen isotope values of modern rainfall in our study area within the heart of the Intertropical Convergence Zone (ITCZ) are dominated by the amount effect and moisture source, and we interpret our data as a paleorainfall proxy. Our data show substantial oxygen isotope variability on centennial to multi-millennial time scales. Further, our paleorainfall time series is strongly correlated with the deuterium excess parameter in Greenland Ice, which suggests that the strength of the tropical hydrological cycle has modulated the flow of low-latitude moisture to Greenland on millennial time scales. Our results indicate a strong coupling between tropical and high latitude paleoclimate, that was likely linked via variations in the strength of the Hadley cell and its associated export of atmospheric moisture to the high latitudes. We observe the wettest periods in Central America when the Caribbean was warmer than 26.5 degrees C and the Caribbean to Pacific (cold tongue) SST gradient was largest, suggesting a combined Atlantic and Pacific Ocean control on ITCZ rainfall.
DE: 1041 Stable isotope geochemistry (0454, 4870)
DE: 1620 Climate dynamics (0429, 3309)
DE: 1635 Oceans (1616, 3305, 4215, 4513)
DE: 1655 Water cycles (1836)
DE: 3344 Paleoclimatology (0473, 4900)
SC: Union [U]
MN: 2007 Fall Meeting