Quantitative reconstruction of Early Pleistocene climate in southeastern Australia and implications for atmospheric circulation |
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| Authors: | JMK Sniderman N Porch AP Kershaw |
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| Institution: | 1. School of Geography and Environmental Science, Monash University, Wellington Road, Monash, Victoria 3800, Australia;2. Department of Archaeology and Natural History, Research School of Pacific and Asian Studies, Australian National University, Canberra, ACT 0200, Australia;1. ARC Centre of Excellence for Environmental Decisions, The NERP Environmental Decisions Hub, Fenner School of Environment and Society, The Australian National University, Canberra, ACT 0200, Australia;2. School of Life and Environmental Science, Deakin University, 211 Burwood Highway, Burwood, Victoria 3125, Australia;1. Department of Meteorology and Centre for Past Climate Change, University of Reading, RG6 6BB, UK;2. Environmental Change Institute, University of Oxford, OX1 3QY, UK;1. Istituto Italiano di Paleontologia Umana, Via U. Aldrovandi 18, 00197 Roma, Italy;2. Dipartimento di Biolologia Ambientale, Sapienza Università di Roma, P.le Aldo Moro 5, 00185 Roma, Italy;3. Istituto di Geologia Ambientale e di Geoingegneria – CNR, Via Salaria Km 29,300, Monterotondo Scalo, 00016 Roma, Italy;4. Dipartimento di Scienze della Terra, Sapienza Università di Roma, P.le Aldo Moro 5, 00185 Roma, Italy;1. Department of Biology & Burke Museum of Natural History and Culture, University of Washington, Box 351800, Seattle, WA 98195, USA;2. Department of Biology, Reed College, 3203 S.E. Woodstock Blvd., Portland, OR 97202, USA;3. Department of Vertebrate Zoology and Anthropology and Center for Comparative Genomics, California Academy of Sciences, 55 Concourse Drive, Golden Gate Park, San Francisco, CA 94118, USA |
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| Abstract: | Today, southeastern Australia experiences a winter-dominated rainfall regime, governed by the seasonal migration of the highly zonal Southern Hemisphere subtropical anticyclone. The late Cenozoic history of this rainfall regime is poorly understood, but it has been widely accepted that its onset was a product of the intensification and northward migration of the subtropical anticyclone, driven by steepening of hemispheric temperature gradients associated with the initiation of extensive Northern Hemisphere glaciation, ～2.6 million years ago (Ma). Here, we use fossil beetle remains from Stony Creek Basin, a small palaeolake record in upland southeastern Australia deposited over ～280,000 years between ～1.84 and 1.56 Ma, to quantitatively reconstruct regional climate during the Early Pleistocene. Climate reconstructions based on coexistence of extant beetle taxa indicate that temperatures were consistently 1–3 °C warmer than present, and rainfall as high as or substantially higher than today, throughout the record. In particular, beetle data indicate that rainfall was similar to today during winter, but 2–2.4 times higher than today during summer. This is consistent with the presence of diverse rainforest pollen also present in the record, and indicates that the modern, winter-dominated rainfall regime was not yet in place by ～1.5 Ma, at least one million years later than previously thought. We suggest that the Southern Hemisphere anticyclonic circulation must have been much less intense during the Early Pleistocene than today, rather than shifted meridionally as previously argued. |
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