Comparison of Glacier Maps a Source of Climatological Information?

Abstract

A small, dome-shaped ice cap named Midtre Folgefonni is situated in southwestern Norway. The ice cap has been covered by vertical aerial photographs on several occasions, and from photographs taken in 1959 and 1981, two special glacier maps have been prepared. The maps, which are provided as a supplement to this paper, have been used to calculate the mass balance of Midtre Folgefonni for the period 1959–81. The results show that large differences occur in the mass balance distribution. The southern sector has lost 10.3 m (water equivalent) of ice, the northwestern sector has lost 15.2 m, the northeastern sector has lost 4.9 m, while the eastern sector has lost only 0.9 m.

It is thought that changes in the wind pattern might result in changes in the amount of snow drifting over the ice cap, and thus are the cause for the uneven mass balance. Wind data from radio sondes launched by the meteorological station at the Sola Airport were therefore used to study the winter wind conditions at the 850 mb-level. The study showed that westerly winds with a Beaufort force ⩾ 4 have increased in frequency from 29% during the period 1951–59 to 43% in the period 1960–79.

This increase in strong winds from the west seems to be responsible for a less pronounced lowering of the glacier surface on the eastern side of the ice cap as compared to the western side. It is assumed that more snow has been transported (drifted) to the east side in the second period than was the case in the 1950's. Repeated mapping of glaciers such as Midtre Folgefonni, seems to be a useful tool for analysing winter wind conditions at higher altitudes.