Talik and cryopeg development related to channel migration has been observed in arctic deltas, but our knowledge on the configuration, properties, and rate of freezeback has remained limited. Along a main channel of the Colville River Delta (Alaska), we integrated subsurface data from 79 boreholes with a remote sensing analysis to measure channel changes in 1948-2013. We found that closed taliks occurred under the active channel and extended into intrapermafrost cryopeg layers under the riverbed/riverbar and active floodplain. Cryopegs as isolated small pockets were also identified at depths in older terrain units. In the study corridor, we estimated that the likelihood of talik and cryopeg occurrence was predominantly (42.2% of area) low, yet a high likelihood was also identified (27.0% of area). Permafrost growth occurred at a rapid rate in the land exposed following channel migration, likely due to the low and delayed release of latent heat as the freezing front progresses downward in the coarse-grained soils of increasing salinity but decreasing temperatures. As the deposits keep cooling, ground ice will continue forming therefore increasing furthermore the salinity of the remaining unfrozen soil pore-water and likely prevent the complete freezeback of the cryopegs developed in relation to channel migration.
K E Y W O R D Scryopeg, epigenetic permafrost, landscape, salinity, talik
Abrupt thaw of ice‐rich permafrost in the Arctic Foothills yielded to the formation of hillslope erosional features. In the infrastructure corridor, we observed thermal erosion and thaw slumping that self‐healed near an embankment. To advance our understanding of processes between infrastructure and hillslope erosional features (INF‐HEF), we combined climate and remote sensing analyses to field investigations to assess an INF‐HEF system and validate our findings in a broader area along the infrastructure corridor. We identified that thaw consolidation along an embankment formed a thermokarst ditch that was ubiquitous in the broader study area, and which was extensively affected by shrubification and supported other positive feedback (e.g., snow accumulation, water impoundment, and weakened vegetation mat). The thermokarst ditch facilitated channelization of cross‐drainage water, thus increasing the terrain vulnerability to thermal erosion that evolved into thaw slumping after heavy rainfalls. The terrain resilience to thaw slumping benefited from the type of ground ice and topography prevailing at our site. The lateral discontinuity of massive ice in an ice‐wedge polygonal system (i.e., interchange soil and massive ice) compounded to a low‐slope gradient with topographic obstacles (e.g., baydzherakhs) decreased slumping activity and supported self‐stabilization.
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