Controls on relief development in glacial landscapes

Glaciers can carve deep valleys and generate steep mountain peaks, and glacial erosion has long been recognized as a relief production process that creates some of the Earth's most picturesque topography. However, previous work suggests that, in some cases, glacial erosion may act as a “buzzsaw” and reduce mountain relief. This occurs because glaciers tend to concentrate erosion at elevations above the snowline, causing a decrease in relief between the snowline and mountain ridgelines. The scenarios under which glaciers enhance versus inhibit relief remain poorly understood. In this study, we test the evolution of relief at a local scale (approximately 2 to 5 km) under various tectonic and climatic conditions using numerical landscape evolution models. The model solves glacier flow with high-order ice physics and simulates glacial erosion as a function of glacier sliding velocity. Results indicate that relief reduction occurs exclusively in regions with slow glacier sliding velocities, predominantly at or below the glacier equilibrium line altitudes (ELAs). To validate these findings, we evaluated the relief evolution in the European Alps. The diverse range of climates and elevations caused varying durations of ice cover during the Quaternary in the Alps, making it possible to substitute space for time across the Alps to understand the relief evolution. We examined the change of relief in relation to reconstructed ice cover duration. Our analysis demonstrates that in regions with slow simulated glacier sliding velocities during the last glaciation, relief decreases with increasing ice cover duration, indicating that slow-flowing glaciers progressively reduce relief. Moreover, these areas exhibit a clustering of elevations around 1500–2000 m, aligning with the past ELA in the Alps. These findings are consistent with our numerical simulation results, and suggest that slow-flowing glaciers at or below the ELA act as agents of relief reduction.