Glacier Albedo:In-situ processes & remote sensing footprints

As our climate warms, glaciers are melting. At high elevations, glacier ice is protected from the sun year- round by a layer of snow that accumulates during the winter seasons. Snow older than one year is called firn. As more snow collects on top of the firn, the firn becomes denser and eventually turns to new glacier ice. In the Alps, the hot summers of the past few years have caused a lot of the snow and firn on the glaciers to melt. This not only prevents new ice from forming, it also exposes more of the existing glacier ice to the sun, making the glacier melt even faster. Snow and firn are very bright and reflect a lot of the incoming radiation back into space. Glacier ice is much darker than snow and absorbs more radiation. This radiation contributes a big part of the energy input for melting the ice. Ice can be more or less dark and absorb more or less energy depending on whether it is covered by dust, rocks, liquid water, or organic material like algae. As the snow covered areas become smaller, the areas where ice is exposed are becoming more important to the overall energy balance of the glaciers. Because of this, it is important to understand the processes that control how dark the ice is in which parts of the glaciers, and whether different glaciers have different ice-darkening processes. The more we know about these processes, the better we can calculate how fast the glaciers will melt. Satellites help us see how dark glacier ice is. They can also show us how much radiation is absorbed at different wavelengths. This gives us clues about the processes at the glacier surface that cause the ice to darken. Satellite data is available globally, so we can learn about the darkening processes in different regions of the world and compare them. However, satellite images do not have a high enough resolution to show everything that is going on at the glacier surface. Some darkening processes may happen at spatial scales too small for the satellites to see, or they may only darken the ice during certain times of the day or during certain seasons, and since satellites do not watch every glacier all the time, such information can be lost. In this project we have two main goals: We want to improve our understanding of darkening processes by collecting data from the glacier surface and integrating this data into what we already know about glacier melt. Like this, we can determine how important different darkening processes are for the overall melt. In a second step, we will compare the data from the glacier surface with high resolution images from an airborne remote sensing campaign, and with lower resolution satellite images. By comparing data at different scales, we can link local observations with larger data sets. The data measured at the glacier surface and from an airplane will help us to better interpret the data measured by satellites. This is important for making better predictions about the future of glaciers.