HR: 1340h
AN: PP33B-0925    [Abstracts]
TI: Holocene Climate Change Over Central Asia and the Himalaya: Latitudinal Dependence On the Monsoon and Midlatitude Eddy Activity
AU: * Bush, A B
EM: andrew.bush@ualberta.ca
AF: University of Alberta, 126 Earth Sciences Building, Edmonton, AB T6G 2E3 Canada
AB: Climate over Asia's mid-high latitudes is dominated by cyclone activity whereas over Asia's subtropical southeastern flank it is dominated by the monsoon. Asian climate is therefore highly sensitive to changes in the planet's orbital configuration, which can alter both the midlatitude eddy activity as well as the strength of the south Asian monsoon. The latitudinal extent of the annual mean Hadley (0-30N), Ferrel (30N-60N), and polar (60N-90N) cells provide natural divisions within which to distinguish those regions influenced by changes in the monsoon from those dominated by midlatitude eddy processes. Although the dynamics within these zonal bands are normally coupled quite tightly, the Himalaya in the central longitudes of Asia largely isolate the dynamics of the tropics-subtropics from those of the mid-high latitudes. Through a suite of numerical AGCM simulations that span the Holocene at 500-year intervals, we investigate the latitudinal dependence of Asian climate change over the past 10,000 years. In the monsoon-dominated tropics, the core of the westerly summer monsoon jet is further north than today during the early Holocene and gradually shifts southward as its strength decreases to today's value, with concomitant changes in precipitation and snowfall over northeast India and the Himalaya. In midlatitudes, increased synoptic eddy activity produces colder and wetter (snowier) conditions during the early Holocene as compared to today. There is a distinct shift towards warmer and drier climate during the mid-Holocene when atmospheric carbon dioxide levels are increasing most rapidly, even though synoptic eddy activity is still relatively high. This mid-Holocene shift towards warmer and drier climate has been seen in a number of proxy records from central Russia.
DE: 3344 Paleoclimatology
DE: 3374 Tropical meteorology
DE: 3319 General circulation
DE: 1620 Climate dynamics (3309)
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2004 AGU Fall Meeting