Mineral aerosols: a comparison of the last glacial maximum and preindustrial Holocene

Abstract

A passive mineral dust aerosol model based on source strengths deduced from polar ice core dust concentrations is introduced into the Canadian Centre for Climate Modelling and Analysis (CCCma) second-generation atmospheric general circulation model (GCMII) and used to compare features of the fine particle mineral dust aerosol in a last glacial maximum (LGM) simulation to those of a preindustrial Holocene (MOD) dust simulation. The resulting dust optical thickness is 8-16 times greater over most of the globe during the LGM. The model displays several seasonal characteristics observed in present-day satellite observations of dust, such as the summer maximum over the Arabian Sea and the seasonal north-south shift of the Sahara-Sahel plume. Both of these features are also present in the LGM simulation, though there are some noticeable differences in seasonal variation of dust between the last glacial maximum and the preindustrial Holocene. Since the simulated dust lifetimes are very similar for the MOD and LGM climates, it seems that increased LGM dust lifetime is not the major reason for the observed increase in dust concentration in polar ice cores during the LGM relative to the present.