Simulated airborne particle size distributions over Greenland during Last Glacial Maximum

Polar ice cores indicate that the deposition of dust from the atmosphere wa s strongly enhanced during Last Glacial Maximum (LGM). The concentration of dust in the ice sheets and in the overlaying atmosphere are not proportion al to each other but are dependent, among other things, on the relative mag nitudes of dry and wet deposition which change with climate. Observed dust particle size distributions in the Greenland ice sheet are shifted toward l arger particles during LGM. By applying common theories for particle I remo val processes we show that the airborne particle size distributions over Gr eenland probably remained the same in the two different climates. This lead s to the conclusion that the airborne dust concentration was even higher du ring LGM than indicated by the enhancement in deposition flux. We suggest a LGM/pre-industrial current climate aerosol ratio (including the soluble fr action) over Greenland of about 90-125 by mass and 75-100 by number.