ENVIRONMENTAL MAGNETIC RECORDS OF ATMOSPHERIC DUST VARIABILITY FROM ARABIA AND ASIA OVER THE LAST 500,000 YEARS

Atmospheric dust affects Earth’s radiative balance and is an important climate forcing and feedback mechanism. Dust is argued to have played an important role in past natural climate changes through glacial cycles, yet temporal and spatial dust variability remain poorly constrained and calculations of the radiative impact of dust over such timescales often assume that a distal response record from Antarctica can be used to represent global dust variations. Environmental magnetism can provide powerful parameters for determining the hematite contents in dust from hyper-arid deserts and can therefore make important contributions to understanding the global dust cycle. We have obtained a high-resolution dust record from the Red Sea (with dust sourced mainly from Arabia) with a precise chronology relative to global sea level/ice volume variability. Our record correlates well with a high-resolution Asian dust record from the Chinese Loess Plateau. The chronology of the Chinese loess is notoriously problematical on millennial timescales. Correlation between these records enables us to import our Red Sea chronology to the Chinese Loess Plateau, which provides the first precise timescale for the Chinese Loess Plateau for the last 500,000 years. The high-resolution records of variability for these two major global dust source regions document a high baseline of dust emissions, even through interglacials, with strong superimposed millennial-scale variability. Conversely, the distal Antarctic record appears biased to sharply delineated glacial/interglacial contrasts. Models based on Antarctic dust records will therefore overestimate the radiative contrast of atmospheric dust loadings on those timescales. Additional differences between Arabian/Asian, circum-Saharan and Antarctic dust records reveals that climate models could be improved by avoiding ‘global mean’ dust considerations and by including large-scale regions with different dust source variability.