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1. A Quantitative Graph-Based Approach to Monitoring Ice-Wedge Trough Dynamics in Polygonal Permafrost Landscapes

   https://doi.org/10.3390/rs13163098  

   Rettelbach, Tabea ; Langer, Moritz ; Nitze, Ingmar ; Jones, Benjamin ; Helm, Veit ; Freytag, Johann-Christoph ; Grosse, Guido ( August 2021 , Remote Sensing)

   null (Ed.)

   In response to increasing Arctic temperatures, ice-rich permafrost landscapes are undergoing rapid changes. In permafrost lowlands, polygonal ice wedges are especially prone to degradation. Melting of ice wedges results in deepening troughs and the transition from low-centered to high-centered ice-wedge polygons. This process has important implications for surface hydrology, as the connectivity of such troughs determines the rate of drainage for these lowland landscapes. In this study, we present a comprehensive, modular, and highly automated workflow to extract, to represent, and to analyze remotely sensed ice-wedge polygonal trough networks as a graph (i.e., network structure). With computer vision methods, we efficiently extract the trough locations as well as their geomorphometric information on trough depth and width from high-resolution digital elevation models and link these data within the graph. Further, we present and discuss the benefits of graph analysis algorithms for characterizing the erosional development of such thaw-affected landscapes. Based on our graph analysis, we show how thaw subsidence has progressed between 2009 and 2019 following burning at the Anaktuvuk River fire scar in northern Alaska, USA. We observed a considerable increase in the number of discernible troughs within the study area, while simultaneously the number of disconnected networks decreased from 54 small networks in 2009 to only six considerably larger disconnected networks in 2019. On average, the width of the troughs has increased by 13.86%, while the average depth has slightly decreased by 10.31%. Overall, our new automated approach allows for monitoring ice-wedge dynamics in unprecedented spatial detail, while simultaneously reducing the data to quantifiable geometric measures and spatial relationships. 

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2. Post-fire stabilization of thaw-affected permafrost terrain in northern Alaska

   https://doi.org/10.1038/s41598-024-58998-5  

   Jones, Benjamin M. ; Kanevskiy, Mikhail Z. ; Shur, Yuri ; Gaglioti, Benjamin V. ; Jorgenson, M. Torre ; Ward Jones, Melissa K. ; Veremeeva, Alexandra ; Miller, Eric A. ; Jandt, Randi ( April 2024 , Scientific Reports)

   In 2007, the Anaktuvuk River fire burned more than 1000 km²of arctic tundra in northern Alaska, ~ 50% of which occurred in an area with ice-rich syngenetic permafrost (Yedoma). By 2014, widespread degradation of ice wedges was apparent in the Yedoma region. In a 50 km²area, thaw subsidence was detected across 15% of the land area in repeat airborne LiDAR data acquired in 2009 and 2014. Updating observations with a 2021 airborne LiDAR dataset show that additional thaw subsidence was detected in < 1% of the study area, indicating stabilization of the thaw-affected permafrost terrain. Ground temperature measurements between 2010 and 2015 indicated that the number of near-surface soil thawing-degree-days at the burn site were 3 × greater than at an unburned control site, but by 2022 the number was reduced to 1.3 × greater. Mean annual ground temperature of the near-surface permafrost increased by 0.33 °C/yr in the burn site up to 7-years post-fire, but then cooled by 0.15 °C/yr in the subsequent eight years, while temperatures at the control site remained relatively stable. Permafrost cores collected from ice-wedge troughs (n = 41) and polygon centers (n = 8) revealed the presence of a thaw unconformity, that in most cases was overlain by a recovered permafrost layer that averaged 14.2 cm and 18.3 cm, respectively. Taken together, our observations highlight that the initial degradation of ice-rich permafrost following the Anaktuvuk River tundra fire has been followed by a period of thaw cessation, permafrost aggradation, and terrain stabilization.

    

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3. Coastal inundation regime moderates the short-term effects of sediment and soil additions on seawater oxygen and greenhouse gas dynamics: a microcosm experiment

   https://doi.org/10.3389/fmars.2023.1308590  

   Regier, Peter ; Ward, Nicholas D. ; Izquierdo, Alex ; Baldwin, Andrew H. ; Day, Donnie ; McElhinny, Julia ; Patel, Kaizad ; Vargas, Rodrigo ; Zheng, Jianqiu ; Myers-Pigg, Allison ( December 2023 , Frontiers in Marine Science)

   The frequency and persistence of tidal inundation varies along the coastal terrestrial-aquatic interface, from frequently inundated wetlands to rarely inundated upland forests. This inundation gradient controls soil and sediment biogeochemistry and influence the exchange of soils and sediments from terrestrial to aquatic domains. Although a rich literature exist on studies of the influence of tidal waters on the biogeochemistry of coastal ecosystem soils, few studies have experimentally addressed the reverse question: How do soils (or sediments) from different coastal ecosystems influence the biogeochemistry of the tidal waters that inundate them? To better understand initial responses of coastal waters that flood coastal wetlands and uplands, we conducted short-term laboratory experiments where seawater was amended with sediments and soils collected across regional gradients of inundation exposure (i.e., frequently to rarely inundated) for 14 sites across the Mid-Atlantic, USA. Measured changes in dissolved oxygen and greenhouse gas concentrations were used to calculate gas consumption or production rates occurring during seawater exposure to terrestrial materials. We also measured soil and water physical and chemical properties to explore potential drivers. We observed higher oxygen consumption rates for seawater incubated with soils/sediments from frequently inundated locations and higher carbon dioxide production for seawater incubated with soils from rarely inundated transect locations. Incubations with soil from rarely inundated sites produced the highest global warming potential, primarily driven by carbon dioxide and secondarily by nitrous oxide. We also found environmental drivers of gas rates varied notably between transect locations. Our findings indicate that seawater responses to soil and sediment inputs across coastal terrestrial-aquatic interfaces exhibit some consistent patterns and high intra- and inter-site variability, suggesting potential biogeochemical feedback loops as inundation regimes shift inland.

    

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4. Decadal‐Scale Aquifer Dynamics and Structural Complexities at a Municipal Wellfield Revealed by 25 Years of InSAR and Recent Groundwater Temperature Observations

   https://doi.org/10.1029/2018WR022552  

   Grapenthin, Ronni ; Kelley, Shari ; Person, Mark ; Folsom, Matthew ( December 2019 , Water Resources Research)

   Over the past 35 years the Buckman wellfield near Santa Fe, New Mexico, experienced production well drawdowns in excess of 180 m, resulting in ground subsidence and surface cracks. Increased reliance on surface water diversions since 2011 has reduced pumping and yielded water level recovery. To characterize the impact of wellfield management decisions on the aquifer system, we reconstruct the surface deformation history through the European Remote Sensing Satellite, Advanced Land Observing Satellite, and Sentinel‐1 Interferometric Synthetic Aperture Radar (InSAR) time series analysis during episodes of drawdown (1993–2000), recovery (2007–2010), and modern management (2015–2018) in discontinuous observations over a 25‐year period. The observed deformation generally reflects changes in hydraulic head. However, at times during the wellfield recovery, the deformation signal is complex, with patterns of uplift and subsidence suggesting a compartmentalized aquifer system. Recent records of locally high geothermal gradients and an overall warming of the system (~0.5°C during the water level recovery) obtained from repeat temperature measurements between 2013 and 2018 constrain a conceptual model of convective heat transfer that requires a vertical permeable zone near an observed fault. To reproduce observed temperature patterns at monitoring wells, high basal heat flow and convective cooling associated with downward flow of water from cool shallow aquifers during the drawdown period is necessary. The fault, however, appears to die out southward or may be locally permeable, as conceptual cross‐sectional hydrologic modeling reproduces the surface deformation without such a structure. Our work demonstrates the importance of incorporating well‐constrained stratigraphy and structure when modeling near‐surface deformation induced by, for instance, groundwater production.

    

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5. Hillslope erosional features and permafrost dynamics along infrastructure in the Arctic Foothills, Alaska

   https://doi.org/10.1002/ppp.2188  

   Stephani, Eva ; Darrow, Margaret M. ; Kanevskiy, Mikhail ; Wuttig, Frank ; Daanen, Ronald P. ; Schwarber, Jaimy A. ; Doré, Guy ; Shur, Yuri ; Jorgenson, Mark T. ; Croft, Peppi ; et al ( April 2023 , Permafrost and Periglacial Processes)

   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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