HR: 09:30h
AN: PP31F-07    [Abstracts]
TI: Simulations of Late Paleozoic Continental Ice Sheets Under Orbital and CO₂ Forcing
AU: * Horton, D E
EM: danethan@umich.edu
AF: Department of Geological Sciences, University of Michigan, 1100 N. University CC Little, Ann Arbor, MI 48109, United States
AU: Poulsen, C J
EM: poulsen@umich.edu
AF: Department of Geological Sciences, University of Michigan, 1100 N. University CC Little, Ann Arbor, MI 48109, United States
AU: Pollard, D
EM: pollard@essc.psu.edu
AF: Earth and Environment Science Institute, The Pennsylvania State University, 2217 Earth- Engineering Sciences Bldg, University Park, PA 16802, United States
AB: The late Paleozoic ice age was the most severe glaciation of the Phanerozoic. Contrasting views of the size, duration, and history of this glaciation have been proposed from glaciological and sedimentological evidence. This study utilizes the GENESIS atmospheric general circulation model coupled to a 3-D ice sheet model to investigate the influence of atmospheric CO₂ concentrations and orbital parameter variations on Pangean glaciation. Our study investigates the effects of a range of atmospheric CO₂ concentrations (140 to 2240 ppm) on late Paleozoic continental glaciation. Additionally, an investigation into the effects of Milankovitch orbital forcing is explored via two independent methods. First, simulations of maximum and minimum insolation orbits were run to determine the largest/smallest equilibrium ice sheet volume achievable under the given CO₂ concentration. Second, a transient time-marching scheme was developed to track the ebb and flow of glacial ice sheet volume through full orbital cycles. Our results highlight the important role of atmospheric CO₂ in determining the distribution, volume, and stability of late Paleozoic ice sheets. At low CO2 levels (< 560 ppm) our model predicts large (1.47×10⁸ km³ maximum), multi-domed ice sheets across Gondwana under both equilibrium and transient orbital conditions. Under equilibrium forcings, orbital variations produce large ice volume (up to 1.3×10⁸ km³) and sea level (up to 245 m) changes. However, under transient forcing, orbital variations lead to much smaller variations in ice volume that would not generate the sea-level changes requisite for cyclothem deposition. In general, the results presented here present a theoretical framework for the reconstruction of late Paleozoic glaciation and aid in the reconciliation of the disparate views of the Late Paleozoic Ice Age.
DE: 0726 Ice sheets
DE: 1626 Global climate models (3337, 4928)
DE: 4930 Greenhouse gases
DE: 4946 Milankovitch theory
DE: 9614 Paleozoic
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Fall Meeting