Piloting novel multi-centennial palaeoclimate records from mainland southeast Australia

Abstract

Abstract. High-resolution palaeoclimate proxies are fundamental to our understanding of the diverse climatic history of the Australian mainland, particularly given the deficiency in instrumental datasets spanning greater than a century. Annually resolved, tree-ring based proxies play a unique role in addressing limitations in our knowledge of interannual to multi-decadal temperature and hydroclimatic variability prior to the instrumental period. Here we present cross-dated ring-width (RW) and minimum blue-intensity (BI) chronologies spanning 70 years (1929 – 1998) for Podocarpus lawrencei Hook.f., the Australian mainland's only alpine conifer, based on nine full-disk cross-sections from Mount Loch in the Victorian Alps. Correlations with climate variables from observation stations and gridded data reveal a significant positive relationship between RW and mean monthly maximum temperatures in winter throughout central Victoria (r = 0.62, p < 0.001), and a significant negative correlation to winter precipitation (r = -0.51, p < 0.001). We also found significant negative correlations between RW and monthly snow depth at Spencer Creek in New South Wales (r = -0.60, p < 0.001). Of the assessed BI parameters, delta blue-intensity (ΔBI; the difference between early- and late-wood BI) displayed the greatest sensitivity to climate, with robust spatial correlations with mean October to December maximum and minimum monthly temperatures (r = -0.43, p < 0.001; r = -0.51, p < 0.001) and July precipitation (r = 0.44, p < 0.001), across large areas of northern Victoria. These promising findings highlight the utility of this species for future work. With the very limited availability of suitable long-lived and cross-datable species on the Australian mainland, these results have significant implications for advancing high-resolution palaeoclimate science in southeastern Australia and for improving our understanding of past climate in the region.