HR: 11:50h
AN: U22B-07    [Abstracts]
TI: A Tropical Template for D-O Events During MIS 3? Results From the Lake Malawi Drilling Project
AU: * Brown, E T
EM: etbrown@d.umn.edu
AF: Large Lakes Observatory, and Department of Geological Sciences University of Minnesota Duluth, Duluth, MN 55812, United States
AU: Johnson, T C
EM: tcj@d.umn.edu
AF: Large Lakes Observatory, and Department of Geological Sciences University of Minnesota Duluth, Duluth, MN 55812, United States
AU: Scholz, C A
EM: cascholz@syracuse.edu
AF: Department of Earth Sciences, Syracuse University, Syracuse, NY 13244, United States
AU: King, J W
EM: ?jking@gso.uri.edu
AF: Graduate School of Oceanography, University of Rhode Island, Narragansett, RI 02882, United States
AU: Cohen, A S
EM: cohen@email.arizona.edu
AF: Department of Geosciences, University of Arizona, Tucson, AZ 85721, United States
AB: As part of the Lake Malawi Drilling Project we have undertaken a 1 cm-scale resolution (ca. 20 yr) XRF scanning study of core from site 2A in the Northern Basin of the lake. We have focused on certain parameters, including Fe, Zr:Ti, and Si:Ti; these may be interpreted to represent changing input of terrigenous sediments (delivered to the lake by rivers), soils developed from weathered volcanic ash (delivered more effectively under drier windier conditions), and biogenic silica, respectively. We present here a record of East African climate since 55 ka that indicates rapid shifts between discrete climate modes that appear to be related to abrupt warming (Dansgaard- Oeschger) and cooling (Heinrich) events observed in Greenland. The events in Malawi appear to correspond to episodes of dry conditions and increased northerly winds. Such conditions may occur at times that southward excursion of the Intertropical Convergence Zone brings the tropical rain belt to the south of the study area. Although the timing of the Malawi events cannot be determined exactly, our independent age model, based on 25 radiocarbon dates and stratigraphic correlations to events dated in a nearby at 63 and 75 ka, implies that they occur prior to their Greenland counterparts, consistent with southward excursions of the ITCZ during Greenland stadials. The magnitude and form of each of the events recorded in Malawi sediments corresponds to the scale of the subsequent Greenland warming. This suggests that a tropical component of climate sets a template for abrupt high northern latitude climate fluctuations associated with the bipolar seesaw.
DE: 1605 Abrupt/rapid climate change (4901, 8408)
DE: 4942 Limnology (0458, 1845, 4239)
DE: 9305 Africa
SC: Union [U]
MN: 2007 Fall Meeting