EAGER: Testing Late-Pleistocene and Holocene Climate Change in Southeastern Australia with Multi-proxy Analyses of Alpine Lake Sediments, Kosciuszko National Park, Australia

Western Washington University, Bellingham WA

Investigators

Abstract

This project is funded, under the auspices of the EArly Concept Grant For Exploratory Research (EAGER) award concept, to test ideas on late-Pleistocene through late-Holocene climate change in southeastern Australia based on multiproxy analyses of sediment cores collected from three alpine tarns (lakes) in the highest portions of the Snowy Mountains, New South Wales, Australia. Despite recent efforts to reconstruct the magnitude and spatial distribution of major post-glacial climate events in the Southern Hemisphere (e.g., Antarctic Climate Reversal, Little Ice Age), key gaps in proxy data, most notably in Australia, hinder these reconstructions; this gap reflects a dearth of sites on the continent that preserve high resolution, continuous paleoclimate records. The alpine tarns in Kosciuszko National Park (KNP), New South Wales, represent notable exceptions to this problem: five tarns have acted as continuous sediment traps since deglaciation 18,000-20,000 years ago All lakes in KNP freeze during the peak of the Austral winter (July-September), which provides stable surfaces for deep coring. Blue Lake was previously cored in the 1970’s, and although analyses of those cores were limited, they indicated that the lake has trapped sediment continuously since deglaciation (>18,000 years ago). With a small grant from Western Washington University (WWU), the researchers collected a pilot core from the lake in 2016 in order to test the viability of collecting continuous records from the lake. Initial analysis of the core on an ITRAX multi-scanner demonstrates that the sediments are well preserved and highly structured. Both visual and X-ray imagery indicate sub-centimeter scale strata throughout the core; based on the age estimates from above, this stratigraphy would provide sub-centennial resolution (ca. 20 year/cm) throughout the core. If borne out by dating, such resolution would be unprecedented in southern Australia. This single core demonstrates the exceptional stratigraphic record preserved in Blue Lake alone, and implies that similar, complementary records likely exist in the other, smaller tarns in the park. To test this, the researchers propose to core two additional tarns in the park: Lake Albina, and Club Lake; although shallower than Blue Lake, both occupy bedrock basins and so are less susceptible to lake-level fluctuations related to droughts than sediment dammed lakes. Their differing sizes, depths, and basin geometries might provide complementary records to Blue Lake, allowing the researchers to distinguish between local and regional signals based on correlation testing of the cores. In addition to collecting cores, a suite of analyses to test the paleoclimate potential of cores from these lakes will be conducted at University of Canterbury/University of Queensland by Australian collaborators under existing Australian funding. The Broader Impacts include providing new data and insights into the frequency and magnitude of possible past droughts and temperature variations as well as informing resource managers in local agencies and water and power utility companies. The project will also provide valuable training of early career scientists and undergraduates and graduate students. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.