Simulated airborne particle size distributions over Greenland during Last Glacial Maximum

Abstract

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