Climate-driven changes in tropical cyclone intensity shape dune activity on Earthʹs largest sand island

In this study historical aerial photos and detailed climatic time series are used to show the geomorphological consequences of a significant decrease in tropical cyclone frequency and intensity in eastern Australia since the early 1980s, leading to rapid dune stabilization on Earthʹs largest sand island and a World Heritage Site, Fraser Island, Australia. It is shown that cyclone frequency and intensity significantly declined in eastern Australia (south of 20°S) since the early 1980s, corresponding with the shift to a positive phase of the Interdecadal Pacific Oscillation (in 1977) and an increased frequency of ENSO events since 1982–83. Using historical aerial photos and remote sensing techniques it is shown that most of Fraser Islandʹs transgressive dune fields were advancing inland during the period between 1948 and 1982, and that tropical cyclones in that period were strong enough to initiate small blow outs (< 1 ha). However, the decline in sand drift potential by wind since 1982 resulted in the contraction of the area of Fraser Islandʹs dune fields, at an average rate of 0.5% of their area per year.