A Stable Oxygen Isotope Approach to Tropical Cyclone Reconstruction Northeast Queensland, Australia
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Long-term high temporal resolution records of tropical cyclone activity are needed to distinguish natural variability from anthropogenically induced changes in tropical cyclone frequency and/or intensity. Existing instrumental and palaeocyclone records are either too short or too coarse in resolution. Stalagmites provide long-term high temporal resolution records which have been proven useful for tropical cyclone reconstructions due to the sensitivity of the isotopic composition of stalagmites to changes in precipitation and other local climate phenomena. In order to reconstruct tropical cyclones in Northeast Queensland, Australia, a stalagmite and a peat core were analyzed. This study presents two climate records: a 220 year sediment record (1778-1997) from Quincan Crater (peat core Qui-1) and a 105 year stalagmite record (1901-2005) from Chillagoe Caves (CH2). Climate reconstructions from these records were compared to instrumental climate data such as precipitation, temperature, and tropical cyclone activity, in order to test the suitability of these samples for reconstructing tropical cyclones within the study area. Temperature reconstructions by branched glycerol dialkyl glycerol tetraether membrane lipid content in sediment samples show a close match with summer temperatures. Oxygen isotope measurements on calcite samples from the stalagmite correlate positively with tropical cyclone frequency. The oxygen isotopes correlate with carbon isotopes, possibly due to a similar environmental control on both isotopic records. Sea surface temperatures in the Niño-4 area (5°S-5°N; 160°E-150°W) and the Southern Oscillation Index show some similarities with oxygen and carbon isotopes in accordance with previous studies. CH2 and Qui-1 are both long term high temporal resolution records with a high potential for reconstructing tropical cyclone activity. Further research is needed to establish relationship between tropical cyclones and the isotopic composition of CH2, as well as to test if Qui-1 is influenced by tropical cyclone activity.