A quantitative Late Quaternary temperature reconstruction from western Tasmania, Australia

Abstract

Late Quaternary temperature estimates from the mid latitudes of the Australian region suggest a breakdown in the tight coupling observed between oceanic and atmospheric temperatures over the recent past that has significant implications for our understanding of the response of the Earth’s climate system to global climate change and orbital forcing. Here, we present a pollen-based quantitative temperature reconstruction from the mid latitudes of Australia that spans the last 135 000 years, enabling us to address this critical issue. Gradient analysis of a pollen dataset inclusive of over 1100 Quaternary and modern pollen spectra demonstrates the dominant influence of temperature over Quaternary pollen composition and vegetation change in western Tasmania, Australia. We develop and apply a transfer function for average annual temperature that performs excellently under cross-validation (r2 ¼ 0.76; RMSEP 1 C), is not influenced by spatial autocorrelation and that reveals a remarkably close correlation between oceanic and atmospheric temperature change over the last 135 000 years. Significantly, we report a substantially lower degree of cooling during the LGM/MIS 2 (3.7e4.2 C below present) than previously estimated; a similar degree of cooling during MIS 4 as the LGM (ca 4 C); and a 1 C warming during the Last Interglacial relative to today. We conclude that atmospheric and oceanic temperature changes in this region have remained coupled throughout the substantial climatic shifts associated with glacialeinterglacial cycles over the last 135 000 years.Western Tasmanian pollen records have great potential as a Southern Hemisphere terrestrial palaeothermometer and are critically located to provide significant input in to debates over the occurrence and influence of regional and global climatic episodes in the Southern Hemisphere.