Long term trend of snow depth at Sonnblick (Austrian Alps) and its relation to climate change

The extensive snow measurement network of the Sonnblick region (Hohe Tauern, Austrian Alps) is used to describe temporal trends of snow-depth as well as its relation to climate change for a high-elevated site of the European Alps (2400-3100 m.a.s.l.). Spatial representativeness of single snow stakes, with readings back to 1928, is derived for maximum snow-depth in May using a spatially dense snow depth probing from glacier mass balance measurements. Long-term trends of snow depth show a significant reduction in the contribution of snow accumulation from core-winter (I December to I March) compared to early and late-winter periods. Largest values of snow-depth since 1928 were measured in the 1940s and 1950s. Comparison of monthly changes in snow-depth with precipitation measurements underlines the high influence of wind drift on snow-depth during winter season froth 1 October to 30 April. Whereas inter-annual variability of maximum snow-depth is better explained by low elevation precipitation measurements than by local (high elevation) precipitation measurements, the longer-term mean of local precipitation measurements, however, fits well to the snow-depth measurements, if a mean snow-density of about 400 kg m(-3) is assumed (which matches field observations). Both maximum snow-depth and winter season precipitation show a clear decreasing trend for inter-annual variability. A statistical relationship between air temperature and fraction of solid precipitation is used for estimation of temporal trends in the fraction of solid precipitation at measurement sites. For summer a decrease of about 1% of solid precipitation per decade was found for the lowest elevated sites whereas fraction of solid precipitation in winter remains stable. Relation between snow-depth and climate is investigated by means of local climate data of Sonnblick-Observatory (SBO) and by means of the North-Atlantic Oscillation Index (NAOI). Whereas winter air-temperature is significantly correlated with the NAOI, for winter precipitation and snow depth on 1 May no correlation was found with NAOI. Copyright (C) 2008 John Wiley & Sons, Ltd.