HR: 0800h
AN: PP51E-0646    [Abstracts]
TI: Late Holocene Variability of Rainfall and the El Niño Southern Oscillation from a Costa Rican Speleothem
AU: * Azouz, A D
EM: azouza@unlv.nevada.edu
AF: University of Nevada, Las Vegas, 4505 S. Maryland Pkwy. Department of Geoscience, Las Vegas, NV 89154-4010 United States
AU: Lachniet, M S
EM: matthew.lachniet@ccmail.nevada.edu
AF: University of Nevada, Las Vegas, 4505 S. Maryland Pkwy. Department of Geoscience, Las Vegas, NV 89154-4010 United States
AU: Asmerom, Y
EM: asmerom@unm.edu
AF: University of New Mexico, Department of Earth and Planetary Sciences, Albuquerque, NM 87131 United States
AU: Polyak, V P
EM: polyak@unm.edu
AF: University of New Mexico, Department of Earth and Planetary Sciences, Albuquerque, NM 87131 United States
AU: Burns, S J
EM: sburns@geo.umass.edu
AF: University of Massachusetts, Amherst, Department of Geosciences Morrill Science Center, Amherst, MA 01003
AB: Although the El Niño/Southern Oscillation (ENSO) is the most important source of interannual climate variability in the tropics, its Holocene history is poorly understood, particularly in Central America. Further investigations are needed to constrain the onset and variability of ENSO throughout the Holocene, and to determine its role in generating regional climate anomalies. To generate a Holocene El Niño-linked rainfall history, stalagmite CT-7 was collected from Terciopelo cave in Barra Honda National Park on the Nicoya Peninsula of Costa Rica. An age model of stalagmite CT-7, developed through high precision U-series analysis of 16 calcite subsamples, suggests that CT-7 grew from ~8110-6300 years B.P., with an oxygen isotope sampling interval of ~4 yr /sample, providing us with a high resolution record of ENSO rainfall variability. In the tropics, δ¹⁸O values of rainfall are inversely correlated with rainfall via the amount effect. Therefore, the δ¹⁸O time series will provide us with a rainfall δ¹⁸O proxy spanning the interval of growth. The δ¹⁸O values range from -7 to -10‰ and the δ¹³C values range from ~ -6 to -12‰. The δ¹⁸O values do not show a dramatic shift in values during the interval of growth, suggesting that rainfall was variable about a consistent mean. We suggest drier periods, forced by El Niño, are represented by higher δ¹⁸O values, while lower δ¹⁸O values reflect La Niña events of increased rainfall. CT-7 grew during a key interval in which many researchers suggest modern ENSO conditions initiated. By evaluating the δ¹⁸O values, we will develop a high resolution record of ENSO and determine its frequency and variability throughout the late Holocene.
DE: 1041 Stable isotope geochemistry (0454, 4870)
DE: 1616 Climate variability (1635, 3305, 3309, 4215, 4513)
DE: 3344 Paleoclimatology (0473, 4900)
DE: 4922 El Nino (4522)
SC: Paleoceanography and Paleoclimatology [PP]
MN: Fall Meeting 2005