Abstract ATM-9709806 Miller, Gifford H. University of Colorado, Boulder ATM-9714893 Fogel, Marilyn L. Carnegie Institute of Washington Drought in the Australian Outback: Milankovitch and Anthropogenic Forcing of the Australian Monsoon Lake Eyre Basin is a monsoon-controlled interior basin covering one-sixth of the Australian continent. A majority of the observed wet and dry cycles of this basin are explained by Milankovitch forcing of the Australian monsoon. The failure of Lake Eyre to fill in the early Holocene despite strong forcing by solar radiation and sea level is hypothesized to be a consequence of systematic burning by the earliest human immigrants. A reduction in the density and composition of vegetation across Australia in the past 50 ka, may have resulted in a significant weakening of monsoon penetration into the interior with a long-term trend towards increased aridity. To test this hypothesis further, this award supports field, analytical, and modeling studies 1) to use newly documented stable-isotope signals in ratite eggshell and bone/teeth of other vertebrates to evaluate changes in precipitation and vegetation composition over the past 70,000 years across northern Australia, 2) to develop a chronology for wet and dry cycles in Lake Gregory, a smaller basin wholly within the monsoon-watered region, 3) to refine the chronology of deflationary events in the Lake Eyre Basin to more rigorously evaluate the correlation to Milankovitch controls, 4) to develop new proxies for paleovegetational reconstructions and 5) complete sensitivity tests evaluating the role of vegetation change on the penetration of monsoon precipitation into the Lake Eyre Basin using General Circulation Models.
