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

Stratigraphic variations of oxygen isotopes in the snow which accumulates d uring the winter at the Norwegian glacier Austre Okstindbreen are not entir ely eliminated after 1-2 months of ablation in the following summer. The re lationship between regional temperature changes and delta O-18 values in th e snowpack is affected by many natural factors, but 1989/90 winter air temp eratures were reflected in the snow which remained on Austre Okstindbreen a t 1350 m a.s.l. in July 1990. There were many variations of delta O-18 valu es in the 4.1 m of snow above the 1989 summer surface, but variations in th e underlying firn were relatively small. Meltwater percolation modifies the initial variations of delta O-18 values in the snowpack. At a site below t he mean equilibrium-line altitude on Austre Okstindbreen, increased isotopi c homogenization within a 10 day period in July accompanied an increase of the mean delta O-18 value. Although the isotopic record at a temperate glac ier is likely to be influenced by more factors than is that at polar glacie rs, it can provide an estimate of the approximate trend of local temperatur e variations.