Friends of the Pleistocene Seminar Series

7:00 PM

Online via Zoom

Special Interest Group event

Climate sensitivity of SE Australia during the last ice age with Tim Barrows of the Chronos Radiocarbon Laboratory at UNSW Sydney

Although only a small area of the Australian mainland was glaciated during the Pleistocene, cold environments were extensive and were a major influence on landscape evolution and biogeography. We dated representative periglacial scree slopes and block deposits using exposure dating, optically stimulated luminescence, and radiocarbon. The deposits indicate a large altitudinal shift in isotherms during the last ice age, of the order of 1300 m. This translates into a temperature difference of 8-10 °C between the last glacial maximum and the present. Periglacial conditions probably affected much of southeastern Australia. The treeless and dry conditions resulted in widespread erosion and increased run off. Combined with increased snow storage within catchments, rivers were paradoxically larger, with high seasonal discharge and sediment loads. Increased discharge into the arid zone filled lake basins such as Lake Mungo which feature some of the earliest traces of human habitation of Australia. Dating reveals the lake filled multiple times before 19,000 years ago, held more than 1 km3 of water at its maximum and fluctuated over a depth of 10 m. The presence of water in Lake Mungo closely corresponds to periods when regional surface temperature was colder than present during the late Pleistocene. Our new data supports a model that decreased evaporation and increased runoff were primarily responsible for increased availability of surface water in the hydrological cycle. The climate of southeastern Australia shows an unexpectedly high degree of sensitivity to the increase from ~190 ppm to 280 ppm CO2.

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