The isotopic record at an alpine glacier and its implications for local climatic changes and isotopic homogenization processes

Abstract

AbstractStratigraphic variations of oxygen isotopes in the snow which accumulates during the winter at the Norwegian glacier Austre Okstindbreen are not entirely eliminated after 1–2 months of ablation in the following summer. The relationship between regional temperature changes and δ18O values in the snowpack is affected by many natural factors, but 1989/90 winter air temperatures were reflected in the snow which remained on Austre Okstindbreen at 1350 m a.s.l. in July 1990. There were many variations of δ18O values in the 4.1m of snow above the 1989 summer surface, but variations in the underlying firn were relatively small. Meltwater percolation modifies the initial variations of δ18O values in the snowpack. At a site below the mean equilibrium-line altitude on Austre Okstindbreen, increased isotopic homogenization within a 10 day period in July accompanied an increase of the mean δ18O value. Although the isotopic record at a temperate glacier is likely to be influenced by more factors than is that at polar glaciers, it can provide an estimate of the approximate trend of local temperature variations.