Late Holocene climate change in northern Australia inferred from the archaeal lipids in Lake Barrine

Understanding long-term climate change is particularly relevant in Australasia, where precipitation exhibits marked variability on annual and decadal timescales. Although numerous studies have investigated hydroclimate change during the Common Era in Australasia, high-quality records covering the late Holocene remain scarce in northern Australia. Here we present an isoprenoid glycerol dialkyl glycerol tetraethers (GDGT) record from Lake Barrine, to evaluate the environmental significance of archaeal lipid-based proxies in the lake system and possible drivers of changes during the late Holocene. The fractional composition of isoprenoid GDGTs in the sediments from Lake Barrine is dominated by GDGT-0 and crenarchaeol. The ratio of crenarchaeol and its regio-isomer (cren/cren'), GDGT-0/crenarchaeol ratios and Methane Index suggest that a dominant contribution of archaeal lipids in Lake Barrine derived from Group I.1a Thaumarchaeota, with a minor contribution from Group I.1b Thaumarchaeota and methanogenic archaea. Centennial-scale variation in cren/cren' ratios correlates well with other hydroclimate records in the tropical Australia, due to a preference of Group I.1a Thaumarchaeota for deeper lakes, and humid climates typically do not offer a large niche for soil Group I.1b Thaumarchaeota. Variability of hydroclimate in northern Australia is linked to the mean position and strength of the intertropical convergence zone. Furthermore, the TEX86 proxy can effectively record lake surface temperature during the past 0.8 kyr, however, a slight increase in the contribution of non-Thaumarchaeota in deeper sediments lead to underestimate of the paleotemperature.