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I study the topographic evolution of the Earth’s surface, the processes that shape it, and how these processes change in space and time. Important topics include the interplay of climate, erosion, and tectonics and assessing the geomorphic impacts of climate change. I’m furthermore interested in how glaciers respond to climate change and how they have shaped our planet over the Quaternary period, that is, the last two and a half million years. In my research, I typically combine fieldwork, laboratory analysis, and computer models. My favorite tools are cosmogenic nuclides, which are rare isotopes produced by cosmic radiation in the uppermost meters of the Earth’s surface, and which allow quantifying rates and dates of surface processes.
Climate, Erosion, Tectonics
The topographic evolution of mountain ranges over geologic time scales is driven by tectonic forces that build relief and erosive forces that destroy relief. Because erosion and sediment transport are influenced by climate, and climate can be affected by tectonically-created topography, climate, erosion, and tectonics are thought to be coupled by feedback processes. Such feedbacks have been shown in modeling studies, but supporting field data is rare and often somewhat ambiguous. In part of my research, I try to test whether such feedbacks truly exist and how we can measure them. The Himalaya, which is characterized by large gradients in tectonics and climate, has been a major focus of my studies.
> Climatic and geologic controls on suspended sediment flux in the Sutlej River Valley, western Himalaya> Tectonic control on 10Be-derived erosion rates in the Garhwal Himalaya, India
> Tectonic control of Yarlung Tsangpo Gorge revealed by a buried canyon in Southern Tibet
> The effect of vegetation cover on millennial-scale landscape denudation rates
Geomorphic Impacts of Climate Change
How do the landscapes we live in and the processes that shape them respond to ongoing climate change? Answering this question and making quantitative predictions requires models and observations to test them. In addition, the inventory of landforms and deposits in a landscape can provide important clues on how surface processes responded to climatic changes in the past. The termination of the last glacial cycle some 15,000 years ago, for example, was associated with large climatic changes both in temperature and precipitation that constitute a natural experiment of the landscape-scale response to climate change.
> Seasonal precipitation gradients and their impact on fluvial sediment flux in the Northwest Himalaya
> Climate-driven sediment aggradation and incision since the Late Pleistocene in the NW Himalaya
Glacial Landscapes
During the last glacial period, valley glaciers and ice caps have been significantly more extensive and contributed to shaping mountainous landscapes in ways, which are not fully understood. Subglacial erosion is probably the most obvious and perhaps important process, but there exist numerous other processes through which glacial landscapes evolve. Steep hillslopes, for example, are too steep to support glacier ice and subglacial erosion plays no direct role. Where glaciers impound on rivers, they can form lakes that are inherently unstable and repeatedly send catastrophic floods to downstream reaches.
> Timing and extent of late Quaternary glaciation in the western Himalaya constrained by 10Be moraine dating in Garhwal, India
> Postglacial denudation of western Tibetan Plateau margin outpaced by long-term exhumation
> Climatic limits to headwall retreat in the Khumbu Himalaya, eastern Nepal
Glaciers
Understanding the evolution of glacial landscapes goes hand in hand with understanding glaciers. During my PhD, I became interested in studying glaciers with satellite images, focusing again on the Himalaya. There, many glaciers are covered by supraglacial debris that is sourced from ice-free hillslopes towering above the ice. Such debris cover has profound influence on surface melt rates and thus glacier dynamics. I’m particularly interested in how debris-covered glaciers respond to climate change and how their debris cover can help us to better understand the evolution of glacial landscapes.
> Glacier-surface velocities in alpine terrain from optical satellite imagery – accuracy improvement and quality assessment> Large surface velocity fluctuations of Biafo Glacier, central Karakoram, at high spatial and temporal resolution from optical satellite images
> Spatially variable response of Himalayan glaciers to climate change affected by debris cover
> Hillslope-glacier coupling: the interplay of topography and glacial dynamics in High Asia
Topographic Analysis
The Earth’s topography (and bathymetry) results from the processes that shape it today and during its recent geological history. For many geomorphic questions, the topography provides valuable information, which can be accessed through analysis of digital elevation models (DEMs). Topographic analyses form an integral part in my research and I am developing new tools for studying DEMs. My colleague Wolfgang Schwanghart and I have put together the TopoToolobox v2, a set of MATLAB functions that can be downloaded from GitHub here.
> Bumps in river profiles: uncertainty assessment and smoothing using quantile regression techniques
> Drainage divide networks - Part 1: Identification and ordering in digital elevation models
> Drainage divide networks - Part 2: Response to Perturbations
Impact Craters
I’m grateful to Thomas Kenkmann (University of Freiburg), who got me involved with research when I was an undergraduate, working as a student assisstant at the Museum of Natural History in Berlin on impact craters. I'll never forget the field work that I conducted for my Diploma thesis in the Upheaval Dome impact structure, Canyonlands National Park, Utah, USA. Although I haven’t been active in this field for a while, I find it still fascinating. From a geomorphic point of view, impact cratering is one of the most important processes shaping planetary bodies.
> Structural record of an oblique impact
> Structure and formation of a central uplift: A case study at the Upheaval Dome impact crater, Utah
All photographs shown on this site were taken by D. Scherler. The figure under Topographic Analysis shows a digital elevation model displayed in Matlab with the TopoToolobox v2.
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