干旱区生态环境知识资源中心

Millennial scale variability in the strength/position of the mid-latitude westerlies, as interpreted from rates of dust deposition in an alpine mire south-eastern Australia, is demonstrated to be a major driver of climate variability during the mid to late Holocene. Dust deposition rates were calculated with a trace element provenance model. This approach is capable of distinguishing between sedimentation of local alluvium and genuine deposition of aeolian dust into the studied mire. Low dust deposition from 6500 to 5500 cal. BP occurred during a period of enhanced south-westerly winds which advected moisture into south-eastern Australia resulting in wet conditions. A subsequent dust pulse at 5500-4000 cal. BP is interpreted as a relaxation in south-westerlies resulting in a more arid phase and possibly enhanced climate variability. Reduced dust deposition between 4000 and 2000 cal. BP indicates a return to increased precipitation/moisture in the lower MDB associated with increased south-westerly geostrophic flow. The onset of more arid conditions after 2000 cal. BP implies a reduction in the frequency of precipitation bearing south-westerly winds. A final further significant finding from this study is the identification of a major dust deposition/wind erosion episode coinciding with the onset of European land clearing and agriculture in Australia. (C) 2011 Elsevier Ltd. All rights reserved.