Why were glacial periods so dusty?

 

Interpreting glacial-interglacial dust flux changes

Dust flux reconstructions from the late Quaternary consistently show that dust emissions from source areas around the world were a factor of 2-4 higher in glacial periods than in interglacials. Is this because dust source regions were systematically drier and have lower vegetation density during glacial periods? Is it because new dust sources developed on continental shelves exposed during sea level lowstands? Is it due to an increased supply of fine-grained sediments from glacial erosion? Or is it due to strengthened surface winds?

Models have variously implicated each of these potential controls on global dust levels in attempting to explain high glacial dust levels, leaving the interpretation of dust flux records quite unclear. In a paper published in Quaternary Science Reviews (McGee et al., QSR 2010), we explore the hypothesis that surface winds - and in particular, high-speed wind gusts - were the dominant cause of high glacial dust levels, and we identify evidence suggesting that aridity, sea level, atmospheric CO2, and glacial erosion are not viable global controls on dust emissions on glacial-interglacial timescales.

Dust fluxes in 3 equatorial Pacific cores (red) track changes in ice volume (black) over the past 500,000 years, with dust fluxes a factor of ~2.5 greater during glacial periods (Winckler et al., Science 2008)