A decadal positive mass balance of very small glaciers in the southeastern European Alps controlled by extreme seasonal precipitation events

Very small glaciers (<0.5 km2) account for more than 80% of the total number of glaciers and more than 15% of the total glacier area in the European Alps. Although small in size, they are a relevant component of the Alpine cryosphere and widely considered as important indicators of climate change. Their sensitivity to global warming is particularly pronounced in maritime areas receiving high mean annual precipitation (MAP). The southeastern European Alps show one of the highest MAP totals in the entire Alpine chain, with up to 3300 mm (water equivalent) in the Julian Alps and a winter snow accumulation of approximately 7 m at 1800 m asl (averaged over the period 1972-2017). As a consequence, very small glaciers and ice/!rn patches are still present in that area at rather low altitudes (1830-2340 m asl). This study seeks to better understand the impact of extreme events on short- to medium-term response of very small glaciers. First, we performed repeated geodetic and direct mass balance measurements on several glaciers during the period 2006-2016, and the results show more than 10% increase in ice volume in the studied decade. This is in accordance with several exceptional winter snow accumulations in the 2000s in the southeastern Alps, promoting a positive mass balance in the following years. This contrasts with a general trend for the European Alps of about a half of the glacier area loss in the period 1850-2000, and even accelerated ice loss after 1980. We then analysed synoptic meteorological conditions leading to the exceptional snowy winters in the 2000s, which appear to be related to the in$uence and modi!cation of some climate indices. Although further summer warming is expected in the next decades, modi!cation of storm tracks and higher occurrence of extreme events during winter might represent a crucial input in driving the evolution of small glacial remnants of this Alpine sector in the near future.