Characterization of Modern and Fossil Mineral Dust Transported to High Altitude in the Western Alps: Saharan Sources and Transport Patterns

Florian Thevenon,Massimo Chiaradia,Thierry Adatte,John Poté,Christoph Hueglin

doi:10.1155/2012/674385

Abstract

Mineral dust aerosols recently collected at the high-altitude Jungfraujoch research station (N, E; 3580 m a.s.l.) were compared to mineral dust deposited at the Colle Gnifetti glacier (N, E; 4455 m a.s.l.) over the last millennium. Radiogenic isotope signatures and backward trajectories analyses indicate that major dust sources are situated in the north-central to north-western part of the Saharan desert. Less radiogenic Sr isotopic compositions of PM10 aerosols and of mineral particles deposited during periods of low dust transfer likely result from the enhancement of the background chemically-weathered Saharan source. Saharan dust mobilization and transport were relatively reduced during the second part of the Little Ice Age (ca. 1690–1870) except within the greatest Saharan dust event deposited around 1770. After ca. 1870, sustained dust deposition suggests that increased mineral dust transport over the Alps during the last century could be due to stronger spring/summer North Atlantic southwesterlies and drier winters in North Africa. On the other hand, increasing carbonaceous particle emissions from fossil fuel combustion combined to a higher lead enrichment factor point to concomitant anthropogenic sources of particulate pollutants reaching high-altitude European glaciers during the last century.

Highlights

Polar ice core studies document enhanced atmospheric crustal dust transport during cold glacial periods, whereas dust archived in Alpine, Himalayan, and Antarctica ice cores reveals higher continental dust deposition during the 20th-century warming [1,2,3,4]
In order to identify long-range mineral dust sources and the associated circulation patterns, we have studied the insoluble dust transported to the top of the Alps during the last millennium
The objectives of this study are (1) to characterize the mineralogy, geochemistry, and isotopic composition (Sr and Nd) of aeolian dust windborne over the Alps during the last millennium and (2) to compare the paleodust characteristics to analog aerosols collected at the Jungfraujoch high-alpine research station and to potential dust source areas and polar ice core records

Summary

Introduction

Polar ice core studies document enhanced atmospheric crustal dust transport during cold glacial periods, whereas dust archived in Alpine, Himalayan, and Antarctica ice cores reveals higher continental dust deposition during the 20th-century warming [1,2,3,4]. The long-range transported mineral dust and sea salt are the most important sources contributing to the aerosol load in Europe (altering the atmospheric circulation and the global radiative forcing [5]) there is a paucity of ice-core data about mid-latitude dust characteristics covering the preindustrial period. In order to evaluate the atmospheric dust transported over Europe during preindustrial times, we have characterized windblown mineral dust archived in an Alpine ice core over the last millennium. Ice-core records reveal complex spatial and temporal patterns of variability, whose understanding relies on the identification of the related dust

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Conclusion