Reconstruction of European Air Pollution from Alpine Ice Cores

Abstract

There is a rather long tradition of glaciological research in theEuropeanAlps with, for instance, 200-m deep boreholes drilled nearly a hundredyearsago in order to measure glacier thickness. However, detailed paleoice-corestudies were not performed before 1977. One of the reasons was thatglaciersin the Alps were generally believed to be temperate. In a temperateglaciermelt-water percolation destroys the chemical stratigraphy of water-solublecomponents, making such a glacier unsuitable for paleo-chemicalinvestigations. However, in mid and low latitudes, the existence ofso-calledcold glaciers (temperature well below the pressure melting point)is stronglydependent on altitude due to the temperature lapse rate in the atmosphere.Inthe Alps, sufficiently cold firn temperatures that suggest a coldglacier aregenerally found above 4000 masl. in the northern part and above 4300masl.in the southern part (Funk, 1994; Suter et al., 2001).Glaciers in the Alps are well suited for the purpose of reconstructingatmospheric concentrations of short-lived species and to documenttheeffects of anthropogenic emissions on air pollution in Europe, sincethey arelocated in the center of the highly populated and industrialized areasofEurope. A good example of such short-lived species are atmosphericaerosolparticles which have attracted attention in climatic research recentlysincetheir cooling effect on the atmosphere might partly compensate thewarmingby anthropogenically emitted greenhouse gases. In order to quantifytheeffect of anthropogenic aerosols, reliable concentration data setsfrom thesource regions are necessary.Glaciochemical records from the European Alps offer the possibilitytotest the reliability of translating ice-core proxy data into paleoclimaticandpaleoatmospheric records by comparing them with corresponding historicalrecords and historical data from meteorological and air qualitymeasurements (Preunkert et al., 2002; Schwikowski et al., 1999a,Wagenbach, 1997). This combination of suitable glacier archives withlongterm,high quality instrumental records available in the vicinity is unique.Alpine ice-core data from pre-industrial times allow the establishmentofnatural concentration levels for various atmospheric species whoseatmospheric cycles are now influenced by human activities (Harnischet al.,1996). However, glaciers in the Alps are retreating rapidly due toglobalwarming, which poses a threat to these valuable archives. For example,partial damage of a glaciochemical record due to melt-water percolationinthe firn part of an ice core drilled at 4200 masl from the Grenzgletscherwasrecently observed (Eichler et al., 2001).