HR: 08:25h
AN: A41F-02    [Abstracts]
TI: Multi-centennial Climate Variability in the Tropical Andes--a Product of Tropical Atlantic Variability
AU: * Baker, P A
EM: pbaker@duke.edu
AF: Duke University, Earth and Ocean Sciences Box 90227, Durham, NC 27708, United States
AU: Fritz, S C
EM: sfritz2@unl.edu
AF: University of Nebraska, Department of Geosciences, Lincoln, NE 68588, United States
AU: Burns, S J
EM: sburns@geo.umass.edu
AF: University of Massachusetts, Department of Geosciences, Amhearst, MA 01003, United States
AU: Rigsby, C A
EM: rigsbyc@ecu.edu
AF: East Carolina University, Department of Geology, Greenville, NC 27858, United States
AU: Ekdahl, E J
EM: eekdahl2@unlnotes.unl.edu
AF: University of Nebraska, Department of Geosciences, Lincoln, NE 68588, United States
AU: Tapia, P M
EM: perico_tapia@yahoo.com
AF: University of Nebraska, Department of Geosciences, Lincoln, NE 68588, United States
AU: Tapia, P M
EM: perico_tapia@yahoo.com
AF: East Carolina University, Department of Geology, Greenville, NC 27858, United States
AB: In the southern tropical Andes, a high-resolution (sub-decadal) record of Holocene precipitation amount has been reconstructed from stable oxygen isotopic ratios determined on carbonate-bearing sediments from Lagos Umayo and Junin (Peru). On orbital timescales, precipitation amount in this region is well known to be influenced by global-scale forcing, not surprising since wet-season insolation varies on precessional timescales by about one-third of the range of the modern annual cycle. On shorter timescales, the reconstructed precipitation amount underwent significant wet/dry alternations typically lasting a few hundred years. The typical amplitude of these alternations is 30% of the annual precipitation amount. Based on the precipitation dependency of modern agricultural yields on the Altiplano, it seems likely that these long-term droughts would have seriously stressed early inhabitants of the region. In the instrumental period, regional precipitation variability on interannual timescales is clearly influenced by Pacific SST variability; e.g. El Nino events produce dry and warm conditions in much of tropical South America including the central Andes. The existence of a Pacific-SST control on Andean lake levels has also been inferred on longer timescales (Bradley et al. 2003). However, as we have previously posited, the reconstructed wet/dry alternations subjectively appear to be in phase with the Holocene Bond cycles, periods of cold SST in the high-latitude North Atlantic and in the tropical north Atlantic. The mechanism by which the tropical Atlantic ocean forces climate variability on the adjacent continent has still not been fully elucidated.
DE: 1637 Regional climate change
DE: 4914 Continental climate records
DE: 4999 General or miscellaneous
DE: 9360 South America
SC: Atmospheric Sciences [A]
MN: 2007 Joint Assembly