HR: 1340h
AN: PP43B-1245    [Abstracts]
TI: Lake Surface Temperature Variability in Lake Malawi Since the Last Glacial Maximum
AU: * Berke, M A
EM: berk0135@umn.edu
AF: Large Lakes Observatory, University of Minnesota, 2205 East 5th Street, Duluth, MN 55812, United States
AU: Johnson, T C
EM: tcj@umn.edu
AF: Large Lakes Observatory, University of Minnesota, 2205 East 5th Street, Duluth, MN 55812, United States
AU: Werne, J P
EM: jwerne@d.umn.edu
AF: Large Lakes Observatory, University of Minnesota, 2205 East 5th Street, Duluth, MN 55812, United States
AU: Powers, L A
EM: oberem@malawi.net
AF: Mzuzu University, P/Bag 208, Luwinga, Mzuzu 2, Malawi
AB: Previous lack of independent lacustrine temperature proxies led to shortcomings in our understanding of continental paleoclimate records. Recent advances in a molecular biomarker paleotemperature proxy, known as TEX₈₆, have led to new insights about tropical paleoclimate. Powers et al. (2005) reported the temperature history of Lake Malawi, East Africa (9-14°S) based on a TEX₈₆ profile in a core from the north basin of the lake. We subsequently questioned whether this thermal history reflected past regional air temperature or the intensity of upwelling in the north basin. We addressed this question by using TEX₈₆ to reconstruct mean annual lake surface temperatures from a sediment core from the central basin of the lake, far from regions of major upwelling. We focus on a continuous, well-dated core interval from 15 ka BP to present. The earliest part of the record following the Last Glacial Maximum (LGM) displays a 1.5°C warming, followed by a 2.5°C cooling during the Younger Dryas (YD). The early Holocene shows abrupt cooling of 3°C around 9.6ka that intensified, reaching the lowest temperature of the record at 7.2ka BP (24.4°C). This cooling is coincident with early Holocene aridity in the region. This is followed by the largest temperature reversal (4°C over 1150 years), reaching the maximum temperature seen in this study, 28.3°C, at about 6ka. These maximum mid-late Holocene temperatures precede a period of extreme drought over equatorial Africa (Gasse, 2000). These results correlate well with the paleotemperature reconstruction from the northern basin of Lake Malawi (Powers et al., 2005), and confirms results as changes in thermal history for this region, and not localized differences in upwelling.
DE: 1055 Organic and biogenic geochemistry
DE: 1605 Abrupt/rapid climate change (4901, 8408)
DE: 1616 Climate variability (1635, 3305, 3309, 4215, 4513)
DE: 4914 Continental climate records
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Fall Meeting