HR: 15:10h
AN: GC53A-10    [Abstracts]
TI: Solar and Volcanic Modulation of Little Ice Age Climate in the Tropical Andes, Venezuela
AU: * Polissar, P J
EM: polissar@geo.umass.edu
AF: University of Massachusetts, Department of Geosciences Morrill Science Center, Amherst, MA 01003 United States
AU: Abbott, M B
AF: University of Pittsburgh, Geology and Planetary Science, Pittsburgh, PA 15260 United States
AU: Wolfe, A P
AF: University of Alberta, Department of Earth and Atmospheric Sciences, Edmonton, AB T6G 2E3 Canada
AU: Rull, V
AF: Universitat Autonoma de Barcelona, Departament de Biologia Animal, Vegetal i Ecologia Bellaterra, Barcelona, 08193 Spain
AU: Bezada, M
AF: Universidad Pedagogica Experimental Libertador, Departamento de Ciencias de la Tierra Avenida Paez, Caracas, El Paraˇso Venezuela
AB: The underlying causes of late-Holocene climate variability in the tropics are incompletely understood. Here, we report a 1500-year reconstruction of climate history in the Venezuelan Andes using lake sediment records from four sites. This reconstruction is based upon accelerator mass spectrometry (AMS) radiocarbon and Pb-210 dating, sedimentology, magnetic susceptibility, geochemistry, pollen and stable isotope (C, N) measurements. In the Laguna Mucubaji watershed four distinct glacial advances occurred between 1250 and 1810 A.D. The earliest advance began during an extended period of higher global volcanic activity. The subsequent three advances were coincident with minima in solar activity (reconstructed from Be-10 and C-14 records). The Mucubajˇ glacial activity in the Venezuelan Andes coincides with other records of Little Ice Age (LIA) glacial advances in S. America. Comparison of modern glacier equilibrium line altitudes (ELAs) in Venezuela with the Mucubaji LIA glacier ELA indicates an ELA depression of at least 300 m. Both a decline in temperature and increase in precipitation are required to explain the ELA depression. The precipitation increase is supported by increased catchment erosion recorded in L. Blanca sediments. Pollen records from two sites in the Venezuelan Andes also indicate wetter and colder conditions during the LIA.
DE: 9360 South America
DE: 3344 Paleoclimatology
DE: 1655 Water cycles (1836)
DE: 1625 Geomorphology and weathering (1824, 1886)
DE: 1650 Solar variability
SC: Global Climate Change [GC]
MN: 2004 AGU Fall Meeting