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1. Consequences of permafrost degradation for Arctic infrastructure – bridging the model gap between regional and engineering scales

   https://doi.org/10.5194/tc-15-2451-2021  

   Schneider von Deimling, Thomas; Lee, Hanna; Ingeman-Nielsen, Thomas; Westermann, Sebastian; Romanovsky, Vladimir; Lamoureux, Scott; Walker, Donald A.; Chadburn, Sarah; Trochim, Erin; Cai, Lei; et al (January 2021, The Cryosphere)

   null (Ed.)

   Abstract. Infrastructure built on perennially frozen ice-richground relies heavily on thermally stable subsurface conditions. Climate-warming-induced deepening of ground thaw puts such infrastructure at risk offailure. For better assessing the risk of large-scale future damage to Arcticinfrastructure, improved strategies for model-based approaches are urgentlyneeded. We used the laterally coupled 1D heat conduction model CryoGrid3to simulate permafrost degradation affected by linear infrastructure. Wepresent a case study of a gravel road built on continuous permafrost (Daltonhighway, Alaska) and forced our model under historical and strong futurewarming conditions (following the RCP8.5 scenario). As expected, the presenceof a gravel road in the model leads to higher net heat flux entering theground compared to a reference run without infrastructure and thus a higherrate of thaw. Further, our results suggest that road failure is likely aconsequence of lateral destabilisation due to talik formation in the groundbeside the road rather than a direct consequence of a top-down thawing anddeepening of the active layer below the road centre. In line with previousstudies, we identify enhanced snow accumulation and ponding (both aconsequence of infrastructure presence) as key factors for increased soiltemperatures and road degradation. Using differing horizontal modelresolutions we show that it is possible to capture these key factors and theirimpact on thawing dynamics with a low number of lateral model units,underlining the potential of our model approach for use in pan-Arctic riskassessments. Our results suggest a general two-phase behaviour of permafrost degradation:an initial phase of slow and gradual thaw, followed by a strong increase inthawing rates after the exceedance of a critical ground warming. The timing ofthis transition and the magnitude of thaw rate acceleration differ stronglybetween undisturbed tundra and infrastructure-affected permafrost ground. Ourmodel results suggest that current model-based approaches which do notexplicitly take into account infrastructure in their designs are likely tostrongly underestimate the timing of future Arctic infrastructure failure. By using a laterally coupled 1D model to simulate linearinfrastructure, we infer results in line with outcomes from more complex 2Dand 3D models, but our model's computational efficiency allows us to accountfor long-term climate change impacts on infrastructure from permafrostdegradation. Our model simulations underline that it is crucial to considerclimate warming when planning and constructing infrastructure on permafrost asa transition from a stable to a highly unstable state can well occur withinthe service lifetime (about 30 years) of such a construction. Such atransition can even be triggered in the coming decade by climate change forinfrastructure built on high northern latitude continuous permafrost thatdisplays cold and relatively stable conditions today. 

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2. Expanding infrastructure and growing anthropogenic impacts along Arctic coasts

   https://doi.org/10.1088/1748-9326/ac3176  

   Bartsch, Annett; Pointner, Georg; Nitze, Ingmar; Efimova, Aleksandra; Jakober, Dan; Ley, Sarah; Högström, Elin; Grosse, Guido; Schweitzer, Peter (November 2021, Environmental Research Letters)

   null (Ed.)

   Abstract The accelerating climatic changes and new infrastructure development across the Arctic require more robust risk and environmental assessment, but thus far there is no consistent record of human impact. We provide a first panarctic satellite-based record of expanding infrastructure and anthropogenic impacts along all permafrost affected coasts (100 km buffer, ≈6.2 Mio km 2 ), named the Sentinel-1/2 derived Arctic Coastal Human Impact (SACHI) dataset. The completeness and thematic content goes beyond traditional satellite based approaches as well as other publicly accessible data sources. Three classes are considered: linear transport infrastructure (roads and railways), buildings, and other impacted area. C-band synthetic aperture radar and multi-spectral information (2016–2020) is exploited within a machine learning framework (gradient boosting machines and deep learning) and combined for retrieval with 10 m nominal resolution. In total, an area of 1243 km 2 constitutes human-built infrastructure as of 2016–2020. Depending on region, SACHI contains 8%–48% more information (human presence) than in OpenStreetMap. 221 (78%) more settlements are identified than in a recently published dataset for this region. 47% is not covered in a global night-time light dataset from 2016. At least 15% (180 km 2 ) correspond to new or increased detectable human impact since 2000 according to a Landsat-based normalized difference vegetation index trend comparison within the analysis extent. Most of the expanded presence occurred in Russia, but also some in Canada and US. 31% and 5% of impacted area associated predominantly with oil/gas and mining industry respectively has appeared after 2000. 55% of the identified human impacted area will be shifting to above 0 ∘ C ground temperature at two meter depth by 2050 if current permafrost warming trends continue at the pace of the last two decades, highlighting the critical importance to better understand how much and where Arctic infrastructure may become threatened by permafrost thaw. 

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3. Permafrost thaw subsidence, sea-level rise, and erosion are transforming Alaska’s Arctic coastal zone

   https://doi.org/10.1073/pnas.2409411121  

   Creel, Roger; Guimond, Julia; Jones, Benjamin_M; Nielsen, David_M; Bristol, Emily; Tweedie, Craig_E; Overduin, Pier_Paul (December 2024, Proceedings of the National Academy of Sciences)

   Arctic shorelines are vulnerable to climate change impacts as sea level rises, permafrost thaws, storms intensify, and sea ice thins. Seventy-five years of aerial and satellite observations have established coastal erosion as an increasing Arctic hazard. However, other hazards at play—for instance, the cumulative impact that sea-level rise and permafrost thaw subsidence will have on permafrost shorelines—have received less attention, preventing assessments of these processes’ impacts compared to and combined with coastal erosion. Alaska’s Arctic Coastal Plain (ACP) is ideal for such assessments because of the high-density observations of topography, coastal retreat rates, and permafrost characteristics, and importance to Indigenous communities and oilfield infrastructure. Here, we produce 21st-century projections of Arctic shoreline position that include erosion, permafrost subsidence, and sea-level rise. Focusing on the ACP, we merge 5 m topography, satellite-derived coastal lake depth estimates, and empirical assessments of land subsidence due to permafrost thaw with projections of coastal erosion and sea-level rise for medium and high emissions scenarios from the Intergovernmental Panel on Climate Change’s AR6 Report. We find that by 2100, erosion and inundation will together transform the ACP, leading to 6-8x more land loss than coastal erosion alone and disturbing 8-11x more organic carbon. Without mitigating measures, by 2100, coastal change could damage 40 to 65% of infrastructure in present-day ACP coastal villages and 10 to 20% of oilfield infrastructure. Our findings highlight the risks that compounding climate hazards pose to coastal communities and underscore the need for adaptive planning for Arctic coastlines in the 21st century. 

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4. Projecting Permafrost Thaw of Sub‐Arctic Tundra With a Thermodynamic Model Calibrated to Site Measurements

   https://doi.org/10.1029/2020JG006218  

   Garnello, A.; Marchenko, S.; Nicolsky, D.; Romanovsky, V.; Ledman, J.; Celis, G.; Schädel, C.; Luo, Y.; Schuur, E. A. G. (June 2021, Journal of Geophysical Research: Biogeosciences)

   Abstract Northern circumpolar permafrost thaw affects global carbon cycling, as large amounts of stored soil carbon becomes accessible to microbial breakdown under a warming climate. The magnitude of carbon release is linked to the extent of permafrost thaw, which is locally variable and controlled by soil thermodynamics. Soil thermodynamic properties, such as thermal diffusivity, govern the reactivity of the soil‐atmosphere thermal gradient, and are controlled by soil composition and drainage. In order to project permafrost thaw for an Alaskan tundra experimental site, we used seven years of site data to calibrate a soil thermodynamic model using a data assimilation technique. The model reproduced seasonal and interannual temperature dynamics for shallow (5–40 cm) and deep soil layers (2–4 m), and simulations of seasonal thaw depth closely matched observed data. The model was then used to project permafrost thaw at the site to the year 2100 using climate forcing data for three future climate scenarios (RCP 4.5, 6.0, and 8.5). Minimal permafrost thawing occurred until mean annual air temperatures rose above the freezing point, after which we measured over a 1 m increase in thaw depth for every 1 °C rise in mean annual air temperature. Under no projected warming scenario was permafrost remaining in the upper 3 m of soil by 2100. We demonstrated an effective data assimilation method that optimizes parameterization of a soil thermodynamic model. The sensitivity of local permafrost to climate warming illustrates the vulnerability of sub‐Arctic tundra ecosystems to significant and rapid soil thawing. 

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5. Estimates of soil taxonomic change due to near‐surface permafrost loss in Alaska

   https://doi.org/10.1002/saj2.20729  

   Jelinski, N A; Pastick, N J; Kholodov, A L; Sousa, M J; Galbraith, J M (September 2024, Soil Science Society of America Journal)

   Abstract Gelisols (permafrost‐affected soils in US Soil Taxonomy) are extensive in Alaska, currently occurring on ∼45% of the land area of the state. Gelisol taxonomic criteria rely on the presence of near‐surface (less than 2 m deep) permafrost, but ongoing climatic and environmental change has the potential to affect the presence of near‐surface permafrost across much of Alaska throughout the 21st century. In this study, we utilized scenarios of near‐surface permafrost loss and active layer deepening through the 21st century under low (SRES B1, RCP 4.5), mid‐ (SRES A1B), and high (SRES A2, RCP 8.5) emissions scenarios, in conjunction with the statewide STATSGO soil map, to generate spatially explicit predictions of the susceptibility of Gelisols and Gelisol suborders to taxonomic change in Alaska. We find that 15%–53% of Alaskan Gelisols are susceptible to taxonomic change by mid‐century and that 41%–69% of Alaskan Gelisols are susceptible to taxonomic change by the end of the century. The extent of potential change varies between suborders and geographic regions, with Gelisols in Northern Alaska being the most resilient to taxonomic change and Western and Interior Alaskan Gelisols most susceptible to taxonomic change. The Orthel suborder is likely to be highly restricted by the late 21st century, while Histels and Tubels are more likely to be of greater extent. These results should be taken into consideration when designing initial survey and re‐mapping efforts in Alaska and suggest that Alaskan Gelisol taxa should be considered threatened soil taxa due to the proportional extent of likely loss. 

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