A seventy-year history of gaseous pollutants in the northern hemisphere from Arctic firn air

Séminaire de Bill Sturges (University of East Anglia, UK), mardi 3 décembre 10-11h, salle Lliboutry, Bât. de Glaciologie

Résumé : It is possible to drill down in to the layer of deep ‘firn’ that overlies the world’s ice caps, and pump air out of this porous snow-ice material. This ‘firn air’ represents air of increasing age with greater depth. Not all atmospheric gases are preserved in firn air, but enough are to begin to build a picture of historic changes in hemispheric-scale ‘background’ air pollution. In this talk I will present some measurements from a campaign in Greenland last year (the “EGRIP” campaign), and show how these might help complement and extend data from earlier Arctic firn air campaigns. The ultimate aim is to reconstruct continuous histories of several gaseous pollutants from the mid-20th century to the present day. As illustrations I will focus on two groups of gases ; (1) industrial chlorinated hydrocarbons that we think are capable of affecting stratospheric ozone ; and (b) non-methane hydrocarbons (NMHCs) and their reaction products that can yield insight in to the state of the “oxidising capacity” of the lower atmosphere.

Par Bill Sturges, School of Environmental Sciences, University of East Anglia, UK