The role of the Australian Monsoon in the western catchment of Lake Eyre, central Australia, during the Last Interglacial

Abstract

Relative changes in monsoon intensity can be deduced from palaeoenvironmental data such as lake level records, shore line features and aeolian/loess deflationary sequences. These data can provide assessment of past changes in the nature and timing of monsoon activity. The Lake Eyre basin (1,300,000 km2), in central Australia, is a key site for determining the nature and extent of monsoon fluctuations through glacial/interglacial cycles. A last interglacial high lake-level phase some time between 90-130 ka is confirmed by both palaeoenvironmental and computer simulated data. This coincides with a time of high sea level and strong orbital forcing of the Asian monsoon, the primary forcing mechanism for the north Australian monsoon. The large monsoon-fed river systems of the Cooper and Diamantina are likely to have contributed most of the inflow to fill this 'megalake' phase of Lake Eyre. Evidence from the Neales River suggests that these smaller and more southerly rivers were also active. This paper examines the likelihood that the relative synchroneity in fluvial and lacustrine activity across the basin at this time is the result of a common climate forcing mechanism. In examining the role of the monsoon in this western catchment of the lake we present two possible scenarios to explain enhanced fluvial activity during the last interglacial.