Mid-Holocene drying of K'gari lakes (subtropical eastern Australia) necessitates re-evaluation of links to the El Niño-Southern Oscillation and future drying risk

The Holocene history of Australia’s hydroclimate is surprisingly poorly understood. This is, in part, because of the relatively weak forcing of Holocene climate versus that of the late Pleistocene. However, it is commonly suggested that eastern Australian climates dried in the late-Holocene and that this was in response to increased activity in the El Niño-Southern Oscillation (ENSO), in particular, the intensification of the El Niño phase of the ENSO cycle. While this has been inferred from numerous locations, data from K'gari (a World Heritage-listed subtropical east coast sand island once known Fraser Island) was amongst the first used to develop this hypothesis and features heavily in discussion of the causes and effects of ENSO intensification. K’gari’s lake systems have significant cultural, environmental and economic value and are a key aspect of the island’s World Heritage status. This study examines published and new radiocarbon dates from three >4.5 m deep K'gari lakes. There was a hiatus in sedimentation in the lakes representing a marked drying event during the middle Holocene (7,640 to 5,600 a BP), followed by wetter late Holocene climate, which contrasts with previous arguments about K’gari’s history. It will also be argued that this phenomenon is observed in other lakes on the eastern Australian margin in a manner previously unrecognised. Hence, there is a need to re-evaluate the notion of ENSO intensification driving late-Holocene drying on the eastern Australian coastal margin. It also indicates that even the deepest K’gari lakes are vulnerable to drying and the risks associated with drying should be considered in their management.