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HR: 0800h
AN: U31A-0015
TI: Radioisotopically Dated Climate Record Spanning the Last Interglacial in Ice from Mount Moulton, West Antarctica
AU: * Popp, T J
EM: trevor.popp@colorado.edu
AF: Institute of Arctic and Alpine Research and Department of Geological Sciences, University of Colorado Campus Box 450, Boulder, CO 80309 United States
AU: Sowers, T
EM: sowers@geosc.psu.edu
AF: Dept of Geosciences and the Earth and Environment Systems Institute , 237 Deike Building Penn State University, University Park, PA 16802 United States
AU: Dunbar, N W
EM: nelia@nmt.edu
AF: N.M.B.G.M.R./E&ES Department, New Mexico Institute of Mining and Technology, Socorro, NM 87801 United States
AU: McIntosh, W C
EM: mcintosh@nmt.edu
AF: N.M.B.G.M.R./E&ES Department, New Mexico Institute of Mining and Technology, Socorro, NM 87801 United States
AU: White, J W
EM: james.white@colorado.edu
AF: Institute of Arctic and Alpine Research and Department of Geological Sciences, University of Colorado Campus Box 450, Boulder, CO 80309 United States
AB: Age models for paleoclimate records extending into and beyond the last interglacial largely rely on either orbital tuning (Milankovitch theory of climate change) or ice flow modeling. Few late Pleistocene paleoclimate records have been radioisotopically dated for testing the Milankovitch theory of global climate change. Within the ice cap near the summit of Mount Moulton, West Antarctica a series of stratigraphic englacial volcanic ash layers (tephra) have been precisely dated with $^{40}$Ar/$^{39}$Ar to between 10 and 500 kyr bp. Using these dated tephra layers as control points we developed radioisotopically dated paleoclimate records. Coherent $\delta$$^{18}$O$_{ice}$, CH$_{4}$, and $\delta$$^{18}$O$_{atm}$ records have been established throughout the last interglacial and the start of the last glacial periods. The Moulton $\delta$$^{18}$O$_{ice}$ record is the first such record of the last interglacial in West Antarctica. The integrity of the Moulton $\delta$$^{18}$O$_{ice}$ record is reinforced by its many shared features with ice stable isotope records at Vostok and EPICA-Dome C in East Antarctica. Similarly, the records derived from the trapped gases (CH$_{4}$ and $\delta$$^{18}$O$_{atm}$) at Moulton correlate well with those of Vostok. A time scale independent of flow modeling or orbital tuning was developed for the Moulton sequence based on four datable tephra layers. One well-dated tephra layer falls in ice that was deposited just before the penultimate glacial termination and suggests that this transition began shortly after 135.8 $\pm$ 1.1 kyr bp. For the penultimate glacial termination, the Moulton age of 135.8 $\pm$ 1.1 agrees extremely well the same feature in the Vostok ice core based on the EGT4 timescale. We discuss the potential for the radioisotopically derived Moulton age model to be applied to any ice core climate record for this interval via gas correlation.
DE: 3344 Paleoclimatology
DE: 1035 Geochronology
DE: 1615 Biogeochemical processes (4805)
DE: 1620 Climate dynamics (3309)
SC: Union [U]
MN: 2004 AGU Fall Meeting