Late Quaternary climates of the Australian arid zone: a review

摘要

Aridity in Australia has generally been associated with glacial intervals of the last few glacial cycles. The causes and nature of aridity varied from north to south over the continent. In northern and central Australia, reduced monsoon rain in global cold stages caused lakes and rivers to dry, vegetation to become more sparse, sand dunes to become active, and dust advection to increase. While the monsoon is correlated with warmer global temperatures and high sea levels overall, the exact timing of the greatest development of the monsoon in Stage 5 remains uncertain. In southeastern Australia, the proxy records give a less clear picture. While vegetation seems to have been more sparse in cold stages and sand dune activity and dust flux consequently greater, records of runoff in rivers and lakes have mixed or opposite behaviour to northern or central Australia. The nature of aridity in southeastern Australia is not analogous to conditions anywhere on the continent today. Greatly reduced temperatures over the central and southern interior, greater influence of snow and periglaciation on runoff, high groundwater tables, lower rainfall and reduced atmospheric carbon dioxide levels may all have contributed to and interacted to produce the reconstructed picture of a cold, sparsely vegetated arid landscape with large rivers and perennial lakes. The largest changes in circulation patterns over the glacial cycle probably occurred in the location and/or intensity of summer tropical convergence in northern Australia. Over southern Australia, changes to the temperature and humidity of the westerly circulation have been more significant than the small fluctuations in latitude of the sub-tropical high pressure ridge.