Distribution and Evolution of Coastal Retrogressive Thaw Slumps along the Yukon Coast, Canada

justine.ramage [ at ] awi.de


Permafrost degradation processes such as thermokarst and thermo-erosion create highly dynamic landforms that reshape Arctic landscapes. Retrogressive thaw slumps (RTSs) are among the most active landforms in the Arctic. RTSs lead to the displacement of large volumes of sediments and are a major source of instability for biomass, hydrology and carbon storage in permafrost terrains. Studies have shown that in various Arctic areas, the number of RTSs has increased tremendously over the past decades. The processes initiating RTSs are well defined; however, little research has been done on regional scale to reveal the major terrain controls on their development. There is a clear need to shed light on the heterogeneous distribution of RTSs in the Arctic. Our research provides new insights into the dynamics of coastal RTSs. It highlights the main geomorphic factors causing RTSs along a 235 km coastal segment of the Yukon Coastal Plain, Canada. We 1) explain differences in the density of RTSs, 2) ascertain the factors controlling their size, and 3) draw an RTSs occurrence susceptibility map, based on the evolution of RTSs in the area over 59 years (1952-2011). We used a large set of high-resolution multispectral satellite images produced in 2011 for geocoding aerial photographs from the 1950s and the 1970s. Using remote sensing, we compared the numbers of RTSs and surface area covered by them in the 1950s, 1970s and in 2011. We highlighted the main terrain controls over the development of RTSs using multivariate and boosted regression trees. Based on the 2011 satellite imagery, we detected 286 coastal RTSs in the study area. Higher densities of RTSs were found in terrains with moderate slopes and high pore ice volumes. RTSs were larger in terrains containing high volumes of massive ice. The number of RTSs has increased by 41.2% during the study period (1952 - 2011), mainly due to important RTSs development on moraine deposits. We did not observe an increase in the size of RTSs throughout the study period. This study shows that the variability of short-term coastline dynamics in the area is highly amplified by permafrost degradation processes acting on ice-rich coasts. As a result, we expect that the reported amounts of sediments released into the Beaufort Sea are related to RTSs development.

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International Conference On Permafrost, 20 Jun 2016 - 24 Jun 2016, Potsdam, Germany.
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Ramage, J. , Irrgang, A. , Morgenstern, A. , Herzschuh, U. and Lantuit, H. (2016): Distribution and Evolution of Coastal Retrogressive Thaw Slumps along the Yukon Coast, Canada , International Conference On Permafrost, Potsdam, Germany, 20 June 2016 - 24 June 2016 .

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