HR: 1340h
AN: PP33A-1008    [Abstracts]
TI: Climatic Forcings of the Last Major Glacial Inception: A GCM Simulation of 115.5 Ka
AU: * Essig, M
EM: messig1@bigred.unl.edu
AF: Univeristy of Nebraska Department of Geosciences, 214 Bessey Hall, Lincoln, NE 68588, United States
AU: Oglesby, R
EM: roglesby2@unl.edu
AF: Univeristy of Nebraska Department of Geosciences, 214 Bessey Hall, Lincoln, NE 68588, United States
AU: Otieno, F
EM: otieno.1@osu.edu
AF: Ohio State University Byrd Polar Research Center, Scott Hall Room 108 1090 Carmack Road, Columbus, OH 43210, United States
AU: Bromwich, D
EM: bromwich.1@osu.edu
AF: Ohio State University Byrd Polar Research Center, Scott Hall Room 108 1090 Carmack Road, Columbus, OH 43210, United States
AB: The onset of Northern Hemisphere glaciation at around 115.5 Ka is thought to have been caused by a number of factors. Two of the most important of these are a reduction in atmospheric CO2 from approximately 380 ppm to 180 ppm, and changes in the earth's eccentricity, precession, and obliquity due to Milankovitch orbital cycles. We used the NCAR CCSM3 GCM in fully coupled mode to simulate the climate at 115.5 ka B.P. The fully-coupled mode includes dynamical atmospheric and oceanic components, as well as sophisticated land surface and sea ice schemes. Sea level and the distribution of the continents were held at present-day values, since they changed little between 0 Ka and 115.5 Ka. Thus, our model simulation can also be thought of as examining the roles of lowered CO2 and orbital configuration in driving glacial inception. In particular, we hypothesize that these climatic forcings will lead to a succession of cool summers and warm wet winters in key regions of the high latitude Northern Hemisphere. In turn, we expect this will be conducive to building the perennial snow pack that is an essential precursor to the Laurentide and Fenno-Scandinavian ice sheets. Though the simulation is still underway at this writing, preliminary results from the first 100 years of the run suggest that this does indeed take place. Key results from the completed run will be presented at the meeting, along with an assessment of how they differ from a present-day CCSM3 control run. Furthermore, in glacial inception regions the performance of both the control run and an existing CCSM3 preindustrial simulation are being compared to ERA40 reanalyses as an additional test of model fidelity. The model simulation is also being verified using all available data from geologic record for the time around 115.5 Ka.
DE: 1626 Global climate models (3337, 4928)
DE: 1631 Land/atmosphere interactions (1218, 1843, 3322)
DE: 3309 Climatology (1616, 1620, 3305, 4215, 8408)
DE: 3337 Global climate models (1626, 4928)
DE: 3344 Paleoclimatology (0473, 4900)
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Fall Meeting