The interplay of tectonic, climatic, and erosional processes controls topography and in turn steep alpine environments are characterized by high erosion rates (Montgomery & Brandon, 2002;Whipple et al., 1999). Climate affects mechanical weathering, including frost cracking processes (Eppes & Keanini, 2017), that breakdown rock (Matsuoka & Murton, 2008). This rock is subsequently transported by rockfall processes (Krautblatter & Dikau, 2007) and results in erosion of rockwalls. Rockwall erosion rates also depend on in situ stress, geological, hydrological, and biological conditions (Krautblatter & Moore, 2014). Field measurements of rockwall erosion using rockfall collectors suggest that rockfall is influenced by seasonal ice segregation (Matsuoka & Sakai, 1999;Sass, 2005c) and volumetric expansion caused by short-term freezing
Temperature loggers provide rock temperature data that incorporates topographic effects on insolation and insulation. Sensitivity tests on frost cracking models showed differences of frost magnitude while frost cracking depth patterns were consistent. Thermo-mechanical models incorporating rock strength and hydraulic properties produced more realistic altitudinal frost cracking patterns.
Mountainous topography reflects an interplay between tectonic uplift, crustal strength, and climate-conditioned erosion cycles. During glaciations, glacial erosion increases bedrock relief, whereas during interglacials relief is lowered by rockwall erosion. Here, we show that paraglacial, frost cracking and permafrost processes jointly drive postglacial rockwall erosion in our research area. Field observations and modelling experiments demonstrate that all three processes are strongly conditioned by elevation. Our findings on catchment scale provide a potential multi-process explanation for the increase of rockwall erosion rates with elevation across the European Alps. As alpine basins warm during deglaciation, changing intensities and elevation-dependent interactions between periglacial and paraglacial processes result in elevational shifts in rockwall erosion patterns. Future climate warming will shift the intensity and elevation distribution of these processes, resulting in overall lower erosion rates across the Alps, but with more intensified erosion at the highest topography most sensitive to climate change.
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