Alpine Glacier Mass Changes During the Past Two Millennia

Abstract

The advance and retreat of mountain glaciers during historical and Holocene time periods refl ect pre-industrial changes in ice mass and corresponding energy fl uxes. Quantitative data analysis can be based on a simple approach comparing assumed steady state situations separated by time intervals of decades to a century. Detailed information spaning the past two millennia is available for the Great Aletsch Glacier, the largest glacier in the European Alps, including an extraordinary number of absolute age and geometry determinations from historical documents, radiocar-bon dating of fossil trees and tree-ring analyses. Rates of mass change and associated energy fl uxes, during the 20 th century as a whole, lie between the average and the extreme of historical values, but appear to have recently increased beyond these limits.