Loss of accumulation zone exposes dark ice and drives increased ablation at Weißseespitze, Austria

In recent years, firn and summer snow cover have
decreased on Alpine glaciers, exposing larger areas of ice
at higher elevations. This reduces albedo and leads to increased melt. To understand mass loss in former accumulation areas under conditions of rapid glacier recession, it
is important to constrain the possible range of ice albedo
in newly firn-free regions, the duration of ice exposure, and
the albedo-ablation relationship. We combine data from an
on-ice weather station (3492 m a.s.l.), ablation stakes, and
remote-sensing-derived albedo to provide an overview of
albedo and ablation in the summit region of Weißseespitze,
the high-point of Gepatschferner (Austria), from 2018 to
2024. Before 2022, low albedo (< 0.4) occurred on 3–
8 d yr−1
. In 2022, 37 d of low albedo values were recorded
by the weather station, and albedo dropped below previously
observed minima of around 0.30 to values similar to those of
the surrounding rock. Albedo remained very low in 2023 and
2024. Ice ablation at the stakes generally increased with the
duration of ice exposure. Losses of up to 1.7 mm w.e. were
recorded in high-melt years. Sensitivity experiments indicate
that a 5 d period of very low albedo conditions (< 0.20) results in about 30 % more modeled surface melt if it occurs
in late July compared to early September, highlighting temporal variability in the impact of ice exposure. The unique
Weißseespitze dataset provides a starting point for further
studies linking causes and effects of albedo changes in former accumulation zones.