Water Tracks and the Evolution of Arctic Watersheds

The Science

To inform understanding of hillslope-channel dynamics under changing climates, researchers examined soil-mantled hillslopes within a roughly 300 km² area of the Seward Peninsula in western Alaska, where discontinuous permafrost is particularly susceptible to thaw and rapid landscape change. In this study, researchers paired high-resolution topographic and satellite data to multi-annual observations of Interferometric Synthetic Aperture Radar (InSAR)-derived surface displacement over a five-year period to quantify spatial variations in topographic change across an upland landscape.

The Impact

Researchers found neither the basin slope nor the presence of knickzones controls the magnitude of recent surface displacements within the study basin, as may be expected under conceptual models of temperate hillslope evolution. Rather, the highest displacement magnitudes tend to occur at the broad hillslope-channel transition zone. In the study area, this zone is occupied by water tracks. Researchers hypothesize gullying within water tracks will outpace infilling by hillslope processes, resulting in the growth of the channel network under future warming.

Summary

Climate and ecology shape hillslopes and the extent of river networks by controlling how much water is available for erosion. These forces also control whether water can erode soil strengthened by ice or roots. The permeability and stability of permafrost hillslopes change with seasonal and long-term warming because of frozen ground’s impermeability and resistance to erosion. This link between temperature and erosion in permafrost landscapes is thus more direct than most geomorphic models developed at lower latitudes presume. Based on the shape of the hillslopes and valleys, researchers related the locations of satellite topographic change to the geomorphic processes that dominate that part of the landscape. This allowed researchers to determine whether the pattern of disturbance across the landscape is related to geomorphic variables, such as slope, or climate-modulated variables, such as soil saturation. Topographic change primarily occurs in saturated areas at the tips of the river network. At these locations, features called “water tracks” form the transition between hillslopes and river valleys. Changes in climate and vegetation in permafrost landscapes are potentially driving water tracks to transition into true channels, expanding the channel network.

Principal Investigator

Joanmarie Del Vecchio
College of William & Mary
[email protected]

Co-Principal Investigator

Joel Rowland
Los Alamos National Laboratory
[email protected]

Program Manager

Daniel Stover
U.S. Department of Energy, Biological and Environmental Research (SC-33)
Environmental System Science
[email protected]

Funding

This research was supported by the Biological and Environmental Research program in the U.S. Department of Energy’s Office of Science, as a contribution to the Next-Generation Ecosystem Experiments Arctic project.

Related Links

• Dataset

References