Abstract Title: A New Late Glacial Record of Changing Hydrology in Subtropical Queensland Derived from Isotopes of Aquatic Cellulose

Abstract Submitted to: PALEOCEANOGRAPHY AND PALEOCLIMATOLOGY

Abstract Text:

Australia is the driest inhabited continent, with the most spatially and temporally variable hydrology. The subtropics of eastern Australia are a vital link between the tropics and the temperate regions, and are very likely to be sensitive to external forcing as they bridge the gap between northern and southern climatic drivers. However, a paucity in quantitative paleoclimate reconstructions and a disparity in climatic interpretations in this region warrants a more comprehensive quantitative model-based paleoclimate reconstruction. Published records show either positive moisture balance throughout the last 30,000 year or hiatus during the LGM which has been interpreted as extended dry periods. In this study, we measured δ13Ccellulose and δ18Ocellulose values of bulk cellulose from a continuous core collected from a perched lake in the Cooloola Sandmass also located in the same region. Compared to the other lakes, no obvious hiatus is observed during the LGM in this record, which covers the last 55,000 years. Cellulose-isotope records were compared with the down core bulk sediment measurements, organic content and pollen data. The pollen data indicates significant shifts in environmental conditions during this time, but it is challenging to interpret based purely on hydroclimate. Negative cellulose isotopic values appear to show a positive moisture balance during the LGM. Whereas during the deglacial, there is a significant shift towards positive isotopic values, suggesting a more negative moisture balance during this period. Based on the hydrological modelling of the lake, we show that this is most likely due to increases in mean air temperatures indicated at nearby sites.