sugiyama_2003.htm
Bulletin of Glaciological Research 20 (2003)
41-47
©Japanese Society of Snow and Ice
Influence of surface debris on summer ablation in Unteraar- and Lauteraargletscher,
Switzerland
Shin SUGIYAMA
Institute
of Low Temperature Science, Hokkaido University, Nishi-8, Kita-19, Sapporo
060-0819 Japan
Abstract
In order to evaluate the influence of surface debris on summer ablation
on a glacier, surface ablation and air temperature were measured from May
to September in 2001 on Unteraar- and Lauteraargletscher. The positive
degree-day factor obtained for a debris-covered surface was 2.98 mm w.e.
K^-1 day^-1, smaller than those obtained for debris free surfaces, 4.45-9.81
mm w.e. K^-1 day^-1. The factors were utilized to compute daily ablation
in each altitudinal range using the positive degree-day method. Results
of the computation show that the debris layer significantly reduces the
total ablation in July and August after the glacier surface changed its
state from snow to debris cover at the lower reach. Thus, it is concluded
that the debris-covered surface substantially contributes to the decrease
in ablation during the mid summer season. The total ablation from May to
August would be larger by 32% if the glacier surface had been assumed to
be entirely debris free.
