HR: 11:20h
AN: U22B-05 INVITED    [Abstracts]
TI: An 85-ka Record of Climate Change in Lowland Central America
AU: * Hodell, D
EM: hodell@ufl.edu
AF: Department of Geological Sciences and Land Use and Environmental Change Institute (LUECI), University of Florida, PO Box 112120, Gainesville, FL 32611, United States
AU: Anselmetti, F
EM: flavio.anselmetti@eawag.ch
AF: Swiss Federal Institute of Aquatic Science & Technology (Eawag), Ueberlandstrasse 133, P. O. Box 611, Dubendorf, 8600, Switzerland
AU: Anselmetti, F
EM: flavio.anselmetti@eawag.ch
AF: Geological Institute, Swiss Federal Institute of Technology (ETH), Universitätstrasse 16, Zurich, 8092, Switzerland
AU: Ariztegui, D
EM: daniel.ariztegui@terre.unige.ch
AF: Section of Earth Sciences, University of Geneva, r. des Maraà®chers 13, Geneva, 1205, Switzerland
AU: Brenner, M
EM: brenner@ufl.edu
AF: Department of Geological Sciences and Land Use and Environmental Change Institute (LUECI), University of Florida, PO Box 112120, Gainesville, FL 32611, United States
AU: Curtis, J
EM: curtisj@ufl.edu
AF: Department of Geological Sciences and Land Use and Environmental Change Institute (LUECI), University of Florida, PO Box 112120, Gainesville, FL 32611, United States
AU: Escobar, J
EM: jaimee@ufl.edu
AF: Department of Geological Sciences and Land Use and Environmental Change Institute (LUECI), University of Florida, PO Box 112120, Gainesville, FL 32611, United States
AU: Gilli, A
EM: agilli@geology.ufl.edu
AF: Department of Geological Sciences and Land Use and Environmental Change Institute (LUECI), University of Florida, PO Box 112120, Gainesville, FL 32611, United States
AU: Gilli, A
EM: agilli@geology.ufl.edu
AF: Geological Institute, Swiss Federal Institute of Technology (ETH), Universitätstrasse 16, Zurich, 8092, Switzerland
AU: Grzesik, D
EM: dustin.grzesik@gmail.com
AF: Department of Geological Sciences and Land Use and Environmental Change Institute (LUECI), University of Florida, PO Box 112120, Gainesville, FL 32611, United States
AU: Guilderson, T
EM: tguilderson@llnl.gov
AF: Center for Accelerator Mass Spectrometry, Lawrence Livermore National Laboratory, PO Box 808, L-397, Livermore, CA 94550, United States
AU: Mueller, A
EM: andreas.mueller@erdw.ethz.ch
AF: Geological Institute, Swiss Federal Institute of Technology (ETH), Universitätstrasse 16, Zurich, 8092, Switzerland
AB: Drill cores obtained from Lake Peten Itza, Guatemala, contain a ~85-kyr record of terrestrial climate from lowland Central America that was used to reconstruct hydrologic changes in the northern Neotropics during the last glaciation. We found that Peten climate varied between wetter conditions during interstadials and a drier state during stadials of Marine Isotope Stage (MIS) 3. The most arid periods were associated with Heinrich Events in the North Atlantic and reductions in the strength of meridional overturning circulation. The pattern of clay-gypsum (wet-dry) oscillations during MIS 3 closely resembles the temperature record from Greenland ice cores and North Atlantic marine sediment cores and precipitation proxies from the Cariaco Basin. Contrary to previous findings, the Last Glacial Maximum (LGM) was moist in the Peten lowlands and vegetation consisted of a temperate pine- oak forest. Greater moisture availability was likely related to increased winter precipitation associated with frequent polar outbreaks (i.e., cold fronts) or "Nortes" (northerly winds,), which occasionally bring rain to northern Guatemala today during the dry season. At the end of the LGM, Peten climate switched from moist to arid conditions during the so-called "Mystery Period" from 18 to 14.7 ka. Moister conditions prevailed during the warmer Bolling-Allerod (14.7 to 12.8 ka), with the exception of a brief return to dry conditions at ~13.8 ka. The onset of the Younger Dryas at 12.8 ka marked the return of dry conditions. Pollen assemblages indicate that a mesic forest had been largely established by ~11.3 ka, but sediment properties suggest that the lake continued to precipitate gypsum until ~10.35 ka. Our results support the hypothesis that summer precipitation was controlled by migrations in the meridional position of the Atlantic ITCZ during the MIS 3 and the last deglaciation. The ITCZ was located farther south during cold periods, especially during Heinrich Events, and arid conditions prevailed in the northern hemisphere Neotropics. During the LGM, however, northern Guatemala may have received significant winter precipitation that is not recorded farther south in the marine record from the Cariaco Basin.
DE: 4914 Continental climate records
SC: Union [U]
MN: 2007 Fall Meeting