HR: 12:05h
AN: PP41D-08    [PDF]
TI: The Greening of the McGill Paleoclimate Model. Part II: Simulation of Holocene Millennial-Scale Natural Climate Variability
AU: * Mysak, L A
EM: lawrence.mysak@mcgill.ca
AF: Dept. of Atmos. & Oceanic Sci., McGill University and Centre for Climate and Global Change Research, 805 Sherbrooke St. West, Montreal, QC H3A 2K6 Canada
AU: Wang, Y
EM: yiwang@zephyr.meteo.mcgill.ca
AF: Dept. of Atmos. & Oceanic Sci., McGill University and Centre for Climate and Global Change Research, 805 Sherbrooke St. West, Montreal, QC H3A 2K6 Canada
AU: Wang, Z
EM: wangz@zephyr.meteo.mcgill.ca
AF: Dept. of Atmos. & Oceanic Sci., McGill University and Centre for Climate and Global Change Research, 805 Sherbrooke St. West, Montreal, QC H3A 2K6 Canada
AU: Brovkin, V
EM: victor@pik-potsdam.de
AF: Potsdam Institute for Climate Impact Research (PIK) Climate System Research Department, P. O. Box 601203, Potsdam, 14412 Germany
AB: Multiple proxy data reveal that the middle Holocene (6 kyr BP) was warmer than the early Holocene (8 kyr BP) as well as the preindustrial period (1700 AD) in most regions of the Northern Hemisphere. This warmth is somewhat counterintuitive because the summer insolation was decreasing during this time. Cooling in the late Holocene (after 6 kyr BP) is hypothesized to be due mainly to the astronomical forcing. This cooling was also accompanied by significant changes in vegetation cover (i.e., treeline retreat from northern high latitudes; the desertification of the Sahara/Sahel region) and a small but gradual increase of atmospheric CO2 concentration (from 260 ppm to 280 ppm). The early-to-middle Holocene warming, on the other hand, is hypothesized to be due in part to ice-albedo feedback in Northern America, associated with decreases in the Laurentide ice sheet, which completely disappeared by 6 kyr BP. The snow-vegetation-albedo feedback is also hypothesized to have played a role in this early warming event. To test the above hypotheses, the earlier geophysical McGill Paleoclimate Model has been coupled to the vegetation model known as VECODE (VEgetation COntinuous DEscription, one of the simpler dynamic global vegetation models), and a number of sensitivity experiments have been performed. The model results illustrate the role that Northern Hemisphere land cover changes played in explaining the natural millennial-scale climate variability from the early Holocene (8 kyr BP) to the preindustrial period (1700 AD).
DE: 0315 Biosphere/atmosphere interactions
DE: 1620 Climate dynamics (3309)
DE: 3309 Climatology (1620)
DE: 3322 Land/atmosphere interactions
DE: 3344 Paleoclimatology
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2003 Fall Meeting