HR: 08:00h
AN: PP31A-01    [PDF]
TI: Polar MM5 Simulations of the Winter Climate of the Laurentide Ice Sheet During the Last Glacial Maximum
AU: * Toracinta, E R
EM: toracinta.1@osu.edu
AF: Polar Meteorology Group Byrd Polar Research Center The Ohio State University, 1090 Carmack Road 108 Scott Hall, Columbus, OH 43210-1002 United States
AU: Bromwich, D H
EM: bromwich@polarmet1.mps.ohio-state.edu
AF: Polar Meteorology Group Byrd Polar Research Center The Ohio State University, 1090 Carmack Road 108 Scott Hall, Columbus, OH 43210-1002 United States
AU: Oglesby, R J
EM: bob.oglesby@nsstc.nasa.gov
AF: NASA Marshall Space Flight Center National Space Science and Technology Center, 320 Sparkman Drive, Huntsville, AL 35805 United States
AU: Wei, H
EM: Helin.Wei@noaa.gov
AF: National Centers for Environmental Prediction, WNP2, NOAA WWB207 5200 Auth Road, Camp Springs, MC 20746-4304 United States
AU: Fastook, J L
EM: fastook@maine.edu
AF: Institute for Quaternary and Climate Studies University of Maine, 303 Edward T. Bryand Global Sciences Center, Orono, ME 04469-5790 United States
AU: Hughes, T
EM: terry.hughes@maine.edu
AF: Institute for Quaternary and Climate Studies University of Maine, 303 Edward T. Bryand Global Sciences Center, Orono, ME 04469-5790 United States
AB: Polar MM5 simulations are conducted using a 60-km domain centered over North America during Last Glacial Maximum (LGM), roughly 21,000 calendar years ago, when much of continent was covered by the Laurentide Ice Sheet (LIS). The objective is to describe the winter atmospheric circulation over North America using a fine-resolution regional climate model that is well suited for high latitude applications. The Polar MM5 LGM boundary conditions include continental ice sheets, appropriate orbital forcing, reduced CO2 concentration, paleovegetation, modified sea surface temperatures, and lowered sea level. Output from a CCM3 (NCAR Community Climate Model version 3) simulation of the LGM is used to provide the initial and lateral boundary conditions for Polar MM5. The model atmosphere responds strongly to the LGM boundary conditions. Cooling over the LIS drives a pronounced wintertime low-level katabatic flow. From November through March the upper level flow is split around a blocking anticyclone over the LIS, with a northern branch over the Canadian Arctic and a southern branch impacting southern North America. This split flow pattern, which is most pronounced in January, has a first order influence on the distribution of precipitation in the model domain and is not present in recent GCM simulations of the LGM. Possible reasons for the presence of the split flow, including ice sheet configuration, model resolution, and model physics, are investigated through a series of sensitivity studies. Each contributes to the winter split jet stream in Polar MM5. Comparisons of model output with available proxy data over North America are also discussed.
DE: 3344 Paleoclimatology
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2003 Fall Meeting