Last Glacial Maximum to Early Holocene Wind Strength in the Mid-latitudes of the Southern Hemisphere from Aeolian Dust in the Tasman Sea

Abstract

Dust transported by Southern Hemisphere mid-latitude westerly winds from Australia and deposited in the Tasman Sea shows no evidence for stronger winds during the last glacial maximum (LGM), compared to the Holocene. Features of the particle-size distributions of the dust do, however, indicate enhanced dry deposition of dust in the LGM changing to rainfall scavenging during deglaciation and the early Holocene as climate ameliorated. From these results it appears that activation of desert dunefields over 40% of Australia during the LGM was the result of a reduction in stabilizing vegetation and more frequent episodes of sand movement rather than of increased wind strength. The LGM climate of inland Australia must have been considerably more stressful for plants as a result of lower precipitation and/or carbon dioxide stress to achieve the implied levels of surface destabilization. Enhanced atmospheric dust loads in the Southern Hemisphere and deposition over Antarctica were most likely the result of greatly expanded source areas in the mid-latitude southern continents and a weaker hydrological cycle rather than greater entrainment or more efficient transport by stronger winds. During the LGM wind strength appears to have varied regionally, and predominantly in high latitudes, rather than uniformly for all zonal winds.