Temperature and hydrological change in central Australia through the last glacial cycle: insights from clumped isotope analysis of lacustrine molluscs

Abstract

Quantitative records of past temperature are crucial for understanding the full range of variability experienced on Earth's surface, and associated drivers. However, Quaternary temperature reconstructions for arid regions are rare, particularly in the Southern Hemisphere, including Australia. Here we utilise the clumped isotope (Δ47) thermometer to estimate carbonate precipitation temperatures for fossil mollusc (Coxiella sp. and Corbicula australis) shells deposited within Quaternary shoreline sediments of three large ephemeral lakes – Kati Thanda-Lake Eyre, Lake Frome, and Lake Callabonna as a way of investigating past climatic conditions in Australia's arid interior throughout the last glacial-interglacial cycle. This study constitutes the longest and most detailed record of past temperature variability to date in central Australia, with estimated mean annual air temperatures (MAAT) inferred to be ∼4–6 °C cooler than modern-day conditions between ∼51 and 33 ka and air temperatures comparable to present interpreted for 196 ± 12 ka and ∼75-57 ka. Calculated MAAT estimates are supported by Δ47 measurements for modern mollusc shells, collected in salt lakes in southern Western Australia, which give accurate modern air temperature estimates within the bounds of uncertainty. Additionally, calculated water temperatures and carbonate δ18O are used to infer past lake hydrology. Carbonate δ18O was driven predominantly by changes in lake water δ18O, rather than by environmental temperature, depicting changes in the evaporative state of the palaeo-lakes. While these findings are limited by the inability to confirm the absence of potential disequilibrium effects and uncertainties regarding the organisms' life cycles, our results demonstrate the value of clumped isotopes for reconstructing palaeoclimate in arid environments and indicate significant temperature variability in Australia's arid interior during the last glacial-interglacial cycle. © 2024 The Authors. Published by Elsevier Ltd. Open Access CC BY 4.0.