HR: 09:30h
AN: PP41C-07    [Abstracts]
TI: Progress Towards Quantitative Reconstruction of the Asian Summer Monsoon Winds From Arabian Sea Sediments During the Holocene
AU: D`Ippolito, C K
EM: purple10000@hotmail.com
AF: Dept. of Geological Sciences, University of South Carolina, Columbia, SC 29208 United States
AU: DuVivier, A K
EM: a_duvivier@ColoradoCollege.edu
AF: Dept. of Physics, Colorado College, Colorado Springs, CO 80903 United States
AU: * Anderson, D M
EM: david.m.anderson@noaa.gov
AF: NOAA's National Climatic Data Center Paleoclimatology Branch, 325 Broadway, E/CC23, Boulder, CO 80305 United States
AU: Gupta, A K
EM: anilg@gg.iitkgp.ernet.in
AF: Department of Geology and Geophysics, Indian Institute of Technology, Kharagpur, WB 721 302 India
AB: Most reconstructions of the Asian summer monsoon during the Holocene rely on proxies that are difficult to interpret directly in terms of wind speed or monsoon rainfall, yet quantitative interpretations are needed both to compare different proxies and to test hypotheses regarding monsoon variability. To develop a quantitative reconstruction we analyzed the relationship between the abundance of fossil G. bulloides (found in coretop sediments) and sea surface temperature, and then used 50 years of observations to determine the relationship between the summer cooling of the sea surface and the strength of the Arabian Sea winds from one year to the next. The cooling of the sea surface is closely related to the large-scale vertical shear in the zonal winds (the Webster-Yang Index), and less well correlated with other monsoon indices such as all-India rainfall, underscoring the difference in indices for wind and rainfall. Uncertainty in the counting and regression errors are large, however the largest source of error appears to be between core variability. We attempted to constrain this by analyzing three different cores. The new reconstruction of the monsoon supports previously published observations of strong monsoon winds during the early Holocene, followed by decreasing winds, with prominent centennial-scale variations during the early Holocene. The quantitative estimates of the Webster-Yang Index reveal that the vertical shear was three times greater than recent decades during the early Holocene, and was reduced but not absent between 3,000 to 1,000 years B.P. We expect the new reconstruction to be most useful in addressing the links between the monsoon and other aspects of the tropical and extratropical circulation such as ENSO and the North Atlantic Oscillation.
DE: 3344 Paleoclimatology (0473, 4900)
DE: 4900 PALEOCEANOGRAPHY (0473, 3344)
DE: 4964 Upwelling (4279)
SC: Paleoceanography and Paleoclimatology [PP]
MN: Fall Meeting 2005