DIRTMAP: the geological record of dust

Atmospheric dust is an important feedback in the climate system, potentialy affecting the radiative balance and chemical composition of the atmosphere and providing nutrients to terreal and marine ecosystems. Yet the potential impact of dust on the climate system, both in the anthropogenically disturbed future and the naturally varying past, remains to be quantified. The geologic record of dust provides the opportunity to test earth system models designed to simulate dust. Records of dust can be obtained from ice cores, marine sediments, and terrestial (loess) deposits. Although rarely unequivocal, these records documents a variety of processes (source, transport and deposits) in the dust cycle, stored in each archieve as changes in clay mineralogy, isotopes, gain size, and concentration of terrigenous materials. Although the extraction of information from each type of archieve is slightly different, the basics controls on these dust indicators are the same. Changes in the dust flux and particle size might be controlled by a combination of (a) source area extent, (b) dust emission efficiency (wind speed) and atmospheric transport, (c) atmospheric residence time of dust, and/or (d) relative contributions of dry settling and rainout of dust. Similarly, changes in mineralogy reflect (a) source are mineralogy and weathering and (b) shifts in atmospheric transport. The combination of this geological data with process-based, forward-modeling schemes in global earth system models provides an excellent means of achieving a comprehensive picture of the global pattern of dust accumulation rates, their controlling mechanisms, and how those mechanisms may vary regionally. The Dust Indicators and Records of Terrestial and MArine Palaeoenvironments (DIRTMAP) data base has been established to provide a global palaeoenvironmental data set that can be used to validate system models simulations of the dust cycle over the past 150,000 years. -cr 2001 Elsevier Science B.V. All right reserved.