Modelling the influence of fluvial and glacial erosion on mountain range relief using a stream-power approach

A common issue in geomorphology is to understand how tectonically induced uplift and climatically driven erosion control the height and steepness of entire mountain ranges. The evolution of characteristic landforms towards a hypothetical steady state topography is well studied for mountain ranges eroded by rivers, but a counterpart for glacial conditions is lacking.

Numerical models of landform evolution are increasingly used to determine the topographic imprint of various processes. However, the complexity arising from multiple processes and possible feedbacks between climate, tectonics and topography leads to process-based but computationally intensive numerical models (e.g., iSOSIA), which have limited applicability on large scales. The open source 2D landform evolution model OpenLEM allows seamless coupling of fluvial and glacial erosion with sediment transport, with almost the same computational efficiency as under purely fluvial conditions (Hergarten, 2021). The calculation of water and ice flow dynamics is not required, as the erosion rate is calculated directly from the properties of the topography (i.e., contributing drainage area and local gradient in the flow direction).

Benchmarking against a process-based landform evolution model (iSOSIA, Egholm et al., 2011) shows that the conversion from fluvial to glacial landscapes produces a consistent glacial signal in the topography, despite local differences in the erosion pattern of both models. Starting from an initial fluvial steady-state mountain range, we investigate the evolution of channel networks with progressive glacial landscape transformation over large time scales where the interaction of earth surface processes with tectonics become relevant. The model shows that both the uplift rates and the parameters of glacial and fluvial erosion control the relief and average slope of the glaciated mountain range. This reflects a situation that is not fundamentally different to fluvial landscapes. Different scenarios are investigated under which conditions a glacial topographic signal accumulates over several glacial cycles or whether the glacial imprint is predominantly removed in interglacial periods.

 

Egholm, D. L., Knudsen, M. F., Clark, C. D., and Lesemann, J. E. (2011): Modeling the flow of glaciers in steep terrains: The integrated second-order shallow ice approximation (iSOSIA), J. Geophys. Res., 116, F02012, doi:10.1029/2010JF001900.

Hergarten, S. (2021): Modeling glacial and fluvial landform evolution at large scales using a stream-power approach, Earth Surf. Dynam., 9, 937–952, https://doi.org/10.5194/esurf-9-937-2021.