Cold firn and ice of high-altitude glaciers in the Alps: measurements and distribution modelling

Abstract

AbstractThe thermal regime of high-altitude accumulation areas in the Swiss Alps was systematically investigated on the Jungfraufirn, Bernese Alps, on the Breithornplateau, Valais Alps, and on Grenzgletscher, Valais Alps. In 1991, 1992 and 1994, temperatures were measured in a deep hole (120 m deep) and in several shallow holes (14–30 m deep). Whereas the wide névé of the Jungfraufirn at 3400–3600 m a.s.l. and the 3800 m high Breithornplateau seems to be predominantly temperate, cold firn and ice temperatures were measured throughout on Grenzgletscher (3900–4450 m a.s.l.). Mean firn temperatures on Grenzgletscher vary strongly and range between −3° and −14°C. A comparison between the measured temperature profiles and a one-dimensional heat-conduction calculation shows that the release of latent heat by penetrating and refreezing meltwater decisively influences the thermal pattern of the firn pack. A multiple linear regression model, based on measured firn temperatures from the European Alps and the parameters altitude and aspect, yields aspect-dependent lower boundaries for the occurrence of cold firn ranging between 3400 (northerly aspects) and 4150 m a.s.l. (southerly aspects). A total of 120 glaciers with cold-firn areas are found when applying the model to glacier inventory data from the European Alps.