Basin-Scale Investigations of Topographic Influence on Permafrost Thaw in Ice Wedge Affected Landscapes
Charles J. Abolt1* (email@example.com), Scott L. Painter2, Ethan T. Coon2, Katrina E. Bennett1, Colleen Iversen2
1Earth and Environmental Sciences Division, Los Alamos National Laboratory, Los Alamos, NM; 2Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN
In the past 30 years, climate change has resulted in a pronounced acceleration of pan-Arctic ice wedge degradation. In tundra settings, subsidence caused by the melting of ice wedges often drives profound changes in microtopography and surface hydrology. One common outcome from these changes is accelerated permafrost thaw beneath newly formed, meter-scale ponds known as thermokarst pools. Previous model-based investigations have predicted that, in some landscapes, the formation of thermokarst pools may accelerate the thaw of presently frozen soil organic carbon more than tenfold by 2100. However, field and satellite-based observations indicate that local trajectories of thermokarst pool formation, and hence the strength of these positive feedbacks, are highly variable and strongly influenced by environmental factors including macroscale topography. Researchers seek to quantify this variability by conducting basin-scale projections of permafrost thaw over next century in a variety of topographic settings. For this work, researchers apply the advanced terrestrial simulator (ATS), a physics-rich integrated surface/subsurface hydrology code that has been specially configured to capture permafrost dynamics in ice wedge-affected terrain. Researchers focus on five landscapes in northern Alaska where rates of thermokarst pool expansion have been observed over the past 13 years using satellite remote sensing, allowing for model validation. The landscapes range from a coastal setting near Utqiaġvik, AK to the northern flanks of the Brooks Range mountains. Researchers designed the analysis to quantify how strongly variability in topographic setting influences thaw-driven changes to surface inundation, and how strongly this variability in surface inundation impacts rates of future permafrost degradation. The research reduces a hitherto unaddressed source of uncertainty in regional projections of thaw in ice wedge-affected terrain. The results of this work will be used to improve the parameterization of inundation fraction within E3SM land models, such that the relationship between permafrost thaw and small pond formation will be modulated by macroscale topography. The new parameterization will enable pan-Arctic assessments of permafrost thaw to account for the influence of regional topography on local and highly variable trajectories of thermokarst pool evolution.