Dust sources and deposition during the last glacial maximum and current climate: A comparison of model results with paleodata from ice cores and marine sediments

Mineral dust aerosols in the atmosphere have the potential to affect the gl obal climate by influencing the radiative balance of the atmosphere and the supply of micronutrients to the ocean. Ice and marine sediment cores indic ate that dust deposition from the atmosphere was at some locations 2-20 tim es greater during glacial periods, raising the possibility that mineral aer osols might have contributed to climate change on glacial-interglacial time scales, To address this question, we have used linked terrestrial biospher e, dust source, and atmospheric transport models to simulate the dust cycle in the atmosphere for current and last glacial maximum (LGM) climates. We obtain a 2.5-fold higher dust loading in the entire atmosphere and a twenty -fold higher loading in high latitudes, in LGM relative to present. Compari sons to a compilation of atmospheric dust deposition flux estimates for LGM and present in marine sediment and ice cores show that the simulated flux ratios are broadly in agreement with observations; differences suggest wher e further improvements in the simple dust model could be made, The simulate d increase in high-latitude dustiness depends on the expansion of unvegetat ed areas, especially in the high latitudes and in central Asia, caused by a combination of increased aridity and low atmospheric [CO2]. The existence of these dust source areas at the LGM is supported by pollen data and loess distribution in the northern continents. These results point to a role for vegetation feedbacks, including climate effects and physiological effects of low [CO2], in modulating the atmospheric distribution of dust.