Abstract ID: 3.11124 | Not reviewed | Requested as: Talk | TBA | TBA

Glaciers, being one of the essential climate variables, are reflecting the effects of changing climate conditions, such as increased temperatures or changes in the precipitation. High-resolution optical satellite data provide an excellent data base to observe multiple glaciers at the same time. Based on high-resolution optical satellite imagery, the main glacier surface classes snow, clean glacier ice, and snow-free debris cover can be automatically separated on small and large glaciers. The automated retrieval of firn areas on mountain glaciers from optical satellite data is still a challenge and requires more research and development to account for the multiple reflectance variations from the multi-annual snow surface. Clouds obscure the Earth’s surface in optical satellite data and are masked.
With the improved observation cycles of the Sentinel-2 missions since 2015, glacier surface conditions can be mapped on multiple dates during the melting season, supporting the monitoring of changing ablation extents on glaciers. Sentinel-2 data over the Alps and the Karakoram were used to generate time series of glacier surface classifications during the melting season of every year between 2015 and 2023.
Analysing these classifications revealed that on glaciers in the Alps, snow areas remaining at the end of summer tend to decrease in recent years. Further, a second minor melt phase after the first winter snow fall is observed in some of these years on glaciers in the Alps. In the Karakoram, the extent of the main snow areas on glaciers in the same years is more stable, but year-to-year variations are mainly observed at the transition zones from snow to ice.
In this presentation, changes in the snow patterns on glaciers in the Alps and Karakoram during the melting period derived from Sentinel-2 data will be demonstrated. Aiming at enhancing our understanding of a changing climate and its impacts on glaciers in different climate zones, the benefits and current limitations of satellite-based glacier surface observations for use in climate models, or in combination with other datasets, will be discussed.
Parts of this work are supported by ESA EXPRO+ AlpGlacier, ESA CCI Glaciers, ESA DTC Glaciers and the ESA X-ECV Karakoram Anomaly.