HR: 0800h
AN: PP41A-0181    [Abstracts]
TI: Late Holocene Climate Change Inferred From Varved Proglacial Lake Sediments on Northeastern Baffin Island, Arctic Canada
AU: * Thomas, E K
EM: ekthomas@buffalo.edu
AF: Department of Geology, University at Buffalo 876 NSC, Buffalo, NY 14260, United States
AU: Briner, J P
EM: jbriner@buffalo.edu
AF: Department of Geology, University at Buffalo 876 NSC, Buffalo, NY 14260, United States
AU: Axford, Y
EM: yaxford@buffalo.edu
AF: Department of Geology, University at Buffalo 876 NSC, Buffalo, NY 14260, United States
AU: Axford, Y
EM: yaxford@buffalo.edu
AF: Institute of Earth Sciences and Department of Geosciences, University of Iceland Askja, Reykjavik, NY 101, Iceland
AB: The Arctic has a disproportionately large response to changes in radiative forcing of climate, and glaciers and arctic lacustrine ecosystems respond sensitively to these changes. Lacustrine ecosystems throughout the Arctic are undergoing rapid regime shifts, including dramatically increased primary productivity and changing aquatic floral and faunal assemblages. Our work on organic lake sediments from northeast Baffin Island shows a large increase in primary productivity, changes in insect (Chironomidae) assemblages including the disappearance of cold stenotherms, and a rise in chironomid-inferred summer water temperatures of at least 1.5°C over the past 50 years, reaching temperatures that were unprecedented in the past 5000 years. Here, we pursue the use of varve thickness, an abiotic temperature proxy, to expand our understanding of late Holocene temperature changes on northeast Baffin Island. We obtained a ¹⁴C- and ^239+240Pu-dated surface core/percussion core pair from a proglacial lake. Together these cores span > 8000 years and the sediments are varved, as verified by the ^239+240Pu analysis, for at least the past 700 years. Magnetic susceptibility was high during the early Holocene, decreased to near-zero values during the mid-Holocene and increased during the past 2500 years to reach the highest values seen in the record around 1000 years ago. Loss-on- ignition had an opposite trend, with the highest values in the mid-Holocene. Sedimentation rate was constant during most of the Holocene (0.03 cm yr ^-1) and increased during the past 1000 years to 0.05 cm yr ^-1. These parameters indicate that following the absence of an active glacier during the middle Holocene, glacier activity initiated ~2500 years ago and reached peak activity over the last 1000 years. Our ongoing work to obtain a varve-thickness record for at least the last 700 years, and its calibration to a nearby weather station, will be presented.
DE: 4902 Anthropogenic effects (1803, 4802)
DE: 4926 Glacial
DE: 4942 Limnology (0458, 1845, 4239)
DE: 4950 Paleoecology
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Fall Meeting