| Popis: |
The recent catastrophic flooding across the world’s driest inhabited continent – Australia – has highlighted an urgent need to understand the climatic (atmospheric) and hydrological (land surface) mechanisms comprising hydroclimate. Records of past hydrologic change may help in this endeavor by informing us about different hydroclimate states and their manifestation on the land surface. By virtue of its antiquity, aridity and relative paucity of available sediment, however, the Australian continent preserves few records of long-term hydroclimate. As a result, we know little about long-term water availability and the drivers of surface hydrology and climate circulation, particularly for the dry inland regions where water resources and sensitive land surfaces need to be carefully managed. One of the few areas in dryland Australia which preserves semi-continuous deposition of hydrologic change is the Willandra Lakes system. The Willandra Lakes are located on the semi-arid desert margin of southeastern Australia, yet its headwaters lie in the temperate eastern highlands. Long-term lake filling and drying is consequently driven by rainfall in the headwaters and hydrologic connectivity both across the catchment and between the lakes. These environmental changes – both long and short in duration – are recorded in the sediments of the downwind transverse dunes (lunettes). In this study we investigate long-term hydrologic connectivity across the catchment and between the lakes. Our approach uses a novel integration of both classical lake-level reconstruction based on lunette sedimentology, stratigraphy and luminescence geochronology, with hydrologic modelling of key event time slices over the last 60 ky, fed into a palaeoclimate model. We characterize the land-surface response to various hydroclimate states, so improving our understanding of dryland atmosphere-hydrosphere interactions. |
