5-3 Geomorphic History Influences Modern Patterns of Ice-wedge Permafrost Degradation

Session: Advances in Mountain Hydrology: Connecting Cryosphere, Surface, and Subsurface Processes

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Abstract:

Permafrost is thawing as the Arctic warms, but it is not thawing uniformly. Ice-wedge permafrost thaw – which impacts much of Arctic Alaska – occurs in distinct spatial and temporal hot spots with uncertain factors driving this heterogeneity. We tracked 20 years of thaw evolution in high-resolution satellite images at a ~1,400 km² study site along the Dalton Highway near Prudhoe Bay, Alaska. More focused mapping of historical aerial photographs at a 1 km² study site extended the temporal record to 74 years (1949-2023) and was paired with field sampling to examine physical drivers of thaw patterns.

Mapping and field data indicate that thaw patterns are associated with the geomorphic history of the landscape. The most long-lasting and intense degradation is spatially clustered on higher-elevation linear features situated atop an abandoned alluvial terrace adjacent to the Sagavanirktok River. These linear features were likely formed from abandoned drainage channels that underwent topographic inversion, potentially due to the larger gravel in the channels resisting aeolian transport more than the finer materials of the surrounding alluvial terrace. The strikingly strong relationship between landform history and permafrost thaw at this site raises important implications about the mechanisms driving degradation. We hypothesize that these hot-spots of thaw are focused on the high-elevation, inverted channels due to a combination of greater exposure to warm summer air and larger concentrations of massive ground ice.

We collected field data on characteristics that impact thaw exposure, including vegetation composition and cover, active layer thickness, and soil physical and chemical properties. We used geospatial analysis of airborne LiDAR and drone multispectral and thermal surveys to estimate ice wedge volume. Preliminary results indicate that ice volume may be greater in the inverted channels, which would imply that the remainder of the alluvial terrace may not be as vulnerable to intense ice-wedge degradation. These landscapes will therefore likely evolve even greater heterogeneity as the Arctic continues warming.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-7607

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