Hydroclimate change in expanding and vulnerable desert margins

01/01/2023 to 31/12/2024

Drylands – regions which are semi-arid to hyperarid - are home to 40% of the global population, and represent one of the most vulnerable regions to climate change. In future decades, anthropogenic global warming is projected to cause an expansion and further aridification (drying) of drylands in the subtropical latitudes, encroaching onto presently more humid zones[1]. Southeastern Australia is recognized as a climate change “hot spot” where this process appears to be accelerating. As one example, an increase in the annual number of fire-season days (dry conditions) recently culminated in the devastating “Black Summer” bushfire disaster of 2019/2020. The conditions observed in southeastern Australia reflect a global phenomenon of accelerating expansion of areas experiencing arid or protracted drought conditions[2], as evidenced by the increase in frequency, scale and intensity of fires in California[3] and Mediterranean Europe[4]. In order to provide the essential context for dryland expansion, and to better understand the underlying processes, it is essential to characterize the trajectories of past change on desert margins prior to our limited instrumental climate records (~100 years).
The aim of this PPP is to investigate paleoclimate records from the vulnerable desert margins of southeastern Australia as an integrated system, combining archives for aridity and climate circulation (aeolian deposits) and hydroclimate (speleothems), with climate modelling to elucidate the trajectory of these environments in a warming world. We will explore archives preserved on the desert margins in “hot spot” southeastern Australia, investigating evidence for and responses to environmental change during more arid and humid periods in the past. Objective [1] will investigate the drivers of reactivation of aeolian (wind-blown) activity in dryland earth-surface deposits, reconstructing the history of activity and indicators for changing climate circulation in the past. Objective [2] will identify past humid conditions from cave speleothems, quantifying temperatures and rainfall sources using novel proxies. Objective [3] will build on global circulation model output and paleoclimate records to identify changes in hydroclimate and atmospheric circulation regionally and in the global context.