Sources and Transport Characteristics of Mineral Dust in Dronning Maud Land, Antarctica

Abstract

Mineral dust in polar ice cores provides unique information about climate induced changes both in dust sources and on the atmospheric transport of dust particles from the source to the polar ice sheets. The presented work investigates changes in sources and transport of dust in the EPICA-DML (EPICA-DML: European Project for Ice Coring in Antarctica - Dronning Maud Land) ice core during Glacial and during the transition to the Holocene. Changes in dust concentration and size were determined on seasonal timescale during cold and warm climate stages in two time slices at 25600 yr BP (Glacial) and 13200 yr BP (Antarctic Cold Reversal (ACR)). The contribution of transport and source to the observed changes in dust concentration were estimated using a one dimensional transport model. Dust sources were investigated by comparing Rare Earth Element (REE) fingerprints from 33 new samples from potential source areas (PSA) with those in the ice core in a quasi-continuous profile (398 out of 613 m) spanning a period from 26600 yr BP to 7500 yr BP. For the first time, data on dust concentration and size in seasonal resolution were obtained, showing differences in seasonal variation in the Glacial and in ACR. It could be shown that during the Glacial dust concentrations exceed concentrations during ACR by a factor of 28, though the size does not differ significantly. On seasonal scale during the Glacial, size changes of 0.2 - 0.3 mikrometer and during the ACR of 0.2 - 0.35 mikrometer occur in phase with mean dust concentration changes of a factor of 7.6 in the Glacial and a factor of 3.5 in the ACR. During the Glacial a clear maximum in concentration and size occurs during austral winter. The difference in dust concentration between Glacial and ACR cannot be explained by transport. On seasonal scale, during the Glacial 30 - 63% of the observed dust concentration changes can be explained by transport, during the ACR even 70 - 100%. This implies that the source did not change significantly during the ACR, during the Glacial by a factor of 1.5 - 2.6, and between Glacial and ACR actually by a factor of ~28. Data show that REE can be used to determine sources of mineral dust in Antarctic ice cores. For the time period 26600 - 15200 yr BP, South America was identified as source for dust in the EPICA-DML ice core. Between 15200 and 7500 yr BP, the source could not be identified unambiguously by using REE fingerprints. However, the South American influence seems to weaken and the influence of other source areas seems to increase in warm periods.