Rapid mass loss and climate-driven dynamics of the Juvfonne ice patch, Norway (2010–2025)

Abstract. Juvfonne is a small ice patch (~0.1 km²) in Jotunheimen, southern Norway, and contains the oldest ice dated in Norway so far. More than 600 artefacts have been detected along the margin. Since 2010 annual investigations of mass balance with point measurements of snow accumulation and ablation have been carried out together with surface elevation and ice patch extent measurements. The outline mapping conducted between 2010 and 2025 demonstrates that the extent of Juvfonne undergoes continuous changes along the entire margin, varying from year to year. The decrease in area from 2010 to 2024 is 46 % from 0.149 km² to 0.081 km². Ice thickness measurements conducted in September 2025 reveal a current maximum thickness of less than 9 meters and an interpolated mean thickness of < 3 meters. Repeat surface elevation surveys from lidar and UAV surveys reveal that Juvfonne has lost 73 % of its volume between 2011 and 2025 and thinned on average 4 m (0.30 m a^-1), the value is sensitive to the outlines used. We compare the mass changes of Juvfonne with neighbouring glaciers in the Galdhøpiggen massif for the period 2011–2020 using repeated lidar surveys revealing that Juvfonne has had a smaller surface thinning than neighbouring glaciers over this period. Interpretation of data from two nearby automatic weather stations show that deposition of windblown snow on Juvfonne causes more snow accumulation than in the surroundings. The snow accumulation is dependent on wind direction and speed. Major snowfall events are associated with storms or synoptic cold fronts with westerly winds and short-term storm events can contribute greatly to the total accumulation. Ablation is related to cumulative positive degree days, but also to winter balance. Results from a Summer Melt Potential Index for the period 2010–2025 reveal a significant intensification of compounding melt events driven by the synergy of temperature, wind, and atmospheric moisture. Juvfonne prevails due to drifting snow and is controlled by topography and can fill up after years with surface lowering. However, the reduction in area and volume over the period 2010–2025 reveals that Juvfonne is vulnerable to the current warming and its current ice may completely vanish with a few warm summers.