Insight of dust provenance in Antarctic ice cores prior to M.I.S. 6 from ice magnetization

Abstract:

The identification of dust provenance and its characteristics is a key issue to understand climate, atmospheric and environmental changes, and provides key constraints to dust transport processes. Many traditional geochemical methods for dust source tracking are not relevant in Antarctic ice cores because of their extremely low dust content, spanning from a few ppb during warm interglacial periods to a few hundreds of ppb, in the case of relatively dustier glacial periods. For the same reason, the Sr-Nd-Pb radiogenic isotope composition of mineral dust in ice cores, that is the most widely-used technique for dust source fingerprint has intrinsic limitations related to dust abundance that drastically limit the temporal information one can achieve. Rock-magnetic properties of aerosol dust, instead, can be measured directly in small ice samples despite its very low concentration. Intensity of isothermal remanent magnetization and coercivity of magnetic minerals are directly related to that of insoluble dust and these magnetic properties are informative of the dust provenance areas. We investigated rock-magnetic properties of aerosol dust in Antartic ice older than M.I.S. 6 in EPiCA Dome-C and Vostok ice core to gather information on dust provenance prior to the last interglacial times. New and previously published results from rock-magnetism suggests that aerosol dust provenance has changed in time during subsequent glacial-interglacial climatic stages. Moreover parallel changes in Dome-C and Vostok sites suggest that such changes result from long-distance dust transportation implying that transportation paths and/or dust sources did not remained the same during the last few glacial-interglacial cycles.