Characteristics and evolution of ice-debris complexes in deglaciating mountain environments investigated by remote sensing and in-situ surveys

Ice-debris complexes are compound landforms, including glaciers, debris-covered glaciers and rock glaciers, that exist at the interface between the glacial, periglacial and paraglacial realms. These landforms are common in many mountain ranges on Earth, but the hydrological and geomorphological role of these ice-debris complexes in the context of deglaciating mountain environments is still not well understood. This is in part due to challenges arising from their position bridging different disciplines, categorisations, and research methodologies.In this talk we present findings from our work based on in-situ investigations (including ground penetrating radar [GPR] and electrical resistivity tomography [ERT)] measurements) and multi-temporal high resolution remotely-sensed image analysis (based on historical aerial images, declassified Corona KH 4 images and contemporary data such as Pléiades satellite images) conducted on selected ice-debris complexes in the Tien Shan, Central Asia and further comparison with examples from the Pamirs, Andes and the European Alps.Results show that the response of debris-covered glaciers, glacier-connected rock glaciers and talus-connected rock glaciers to climate change strongly differs, partly due to the different sources and amount of debris and ice inputs. The presence and distribution of massive ice varies across geomorphic units and is linked to the types of glacial-periglacial interaction. For example, we identify a significant amount of ice buried beneath debris cover in glacier forefields in transition to rock glaciers and in the glacier-connected rock glacier parts. Debris supply is important in controlling the development and flow activity of the morphological units. The response of rock glaciers to climate change is heterogenous with overall increasing velocities and on average only slight surface elevation changes. Glacier-connected rock glaciers flow on average faster than talus-connected rock glaciers. DEM differencing reveals slight increases in surface elevation at the rock glacier termini while debris-covered glaciers show on average a clear signal of surface lowering and decreasing velocities. This highlights the importance of understanding of the debris-sources and the interplay between the glacial and periglacial components of the ice-debris complexes when considering the hydrological and geomorphic role of these landforms.