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This dataset documents the occurrence, distribution, and characteristics of cryptic ice wedge networks in the Yukon-Kuskokwim Delta (YKD), Alaska. The dataset is derived from remote sensing analyses, field-based permafrost coring, ground-penetrating radar (GPR) surveys, and stable water isotope analyses. High-resolution aerial orthoimagery from 2018 enabled the identification of ~50 linear kilometers (km) of ice wedge trough networks within a 60 square kilometers (km²) study area near Bethel, Alaska, revealing ice wedge networks previously undocumented in the region. Fieldwork in 2023 and 2024 confirmed the presence of ice wedges up to 1.5 meter (m) wide and 2.5 m tall, with wedge tops averaging 0.9 m below the surface. GPR transects identified additional ice wedges beyond those visible in imagery, suggesting that remote sensing analyses may underestimate their true abundance. Coring of polygon centers revealed a suite of late-Quaternary deposits, including early Holocene peat, ice-rich late-Pleistocene permafrost (reworked Yedoma), charcoal layers indicating past tundra fires, and the Aniakchak CFE II tephra (~3,600 calendar years before present [cal yrs BP]). Stable water isotope analyses of wedge ice (mean δ¹⁸O = -15.7 ‰, δ²H = -113.1 ‰) indicate relatively enriched values compared to other Holocene ice wedges in Alaska, reflecting the region's warm maritime climate influence. Expanding the mapping analysis across the YKD using very high-resolution satellite imagery, we found that 95 % of observed ice wedge networks occur at elevations between 4 and 80 meters above sea level (m asl), predominantly within tundra vegetation classes. These areas, covering ~32 % of the YKD tundra region, may contain additional ice wedges, peat deposits, and relict Yedoma. This dataset provides a new framework for understanding the spatial distribution and environmental controls on ice wedge development in warm permafrost regions, with implications for permafrost resilience, climate change vulnerability, and land use planning in the YKD. 

The Northwest Coast of North America stretches 4000 km from Bering Strait to Washington State. Here we review the history of glaciation, sea level, oceanography, and climate along the Northwest Coast and in the subarctic Pacific Ocean during the Last Glacial Maximum and deglaciation. The period of interest is Marine Isotope Stage 2 between ca. 29,000 calendar years ago (29 ka) and 11,700 calendar years ago (11.7 ka). The glacial history of the Northwest Coast involved multiple glacial systems responding independently to latitudinal variations in climate caused by changes in the North American ice sheets and in the tropical ocean-atmosphere system. Glaciers reached their maximum extents 1–5 kyrs later along the Northwest Coast than did large sectors of the Laurentide and Fennoscandian Ice Sheets. Local, Last Glacial Maxima were reached in a time-transgressive, north to south sequence between southwestern Alaska and Puget Sound. The history of relative sea level along the Northwest Coast during Marine Isotope Stage 2 was complex because of rapid isostatic adjustments by a thin lithosphere to these time-transgressive glacial fluctuations. Multiple lines of evidence suggest Bering Strait was first flooded by the sea after 11 ka and that it probably did not assume its present-day oceanographic functions until after 9 ka. The coldest intervals occurred during Heinrich Event 2 (ca. 26–23.5 ka), again between ca. 23 and 21.5 ka, and during Heinrich Event 1 (ca. 18–15 ka). During these times, mean annual sea surface temperatures cooled by 5o to 8o C in the Gulf of Alaska, and glacial equilibrium-line altitudes fell below present sea level in southern Alaska and along the Aleutian Island chain. Sea ice episodically expanded across the subarctic Pacific in winter. Oceanographic changes in the Gulf of Alaska tracked variations in the vigor of the Asian Summer Monsoon. The deglaciation of the Northwest Coast may have served as the trigger for global climate changes during deglaciation. Starting ca. 21 ka, marine-based glaciers there were increasingly destabilized by rising eustatic sea level and influxes of freshwater and heat associated with the rejuvenation of the Asian Summer Monsoon. Rapid retreat of marine-based glaciers began ca. 19 ka and released large numbers of ice bergs and vast amounts of freshwater into the Northeast Pacific. Resultant cooling of the North Pacific may have been teleconnected to the North Atlantic through the atmosphere, where it slowed Atlantic Meridional Overturning Circulation and initiated the global effects of Heinrich Event 1, ca. 18–15 ka. During the Younger Dryas, ca. 12.8–11.7 ka, mean annual sea surface temperatures were 4o to 6o C cooler than today in the Gulf of Alaska, and sea ice again expanded across the subarctic Pacific in winter. Conditions of extreme seasonality characterized by cold, dry winters and warm, steadily ameliorating summers caused by the southward diversion of the Aleutian Low in winter may explain the previously enigmatic records of Younger Dryas climate along the Northwest Coast. 

Abstract 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. 

### Access Photos of ~50 permaforst boreholes and associated cores can be accessed and downloaded from the 'AR\_Fire\_Core_Photos' directory via: [https://arcticdata.io/data/10.18739/A2251FM9P/](https://arcticdata.io/data/10.18739/A2251FM9P/) ### Overview The Anaktuvuk River tundra fire burned more than 1,000 square kilometers of permafrost-affected arctic tundra in northern Alaska in 2007. The fire is the largest historical recorded tundra fire on the North Slope of Alaska. Fifty percent of the burn area is underlain by Yedoma permafrost that is characterized by extremely high ground-ice content of organic-rich, silty buried soils and the occurrence of large, syngenetic polygonal ice wedges. Given the high ground-ice content of this terrain, Yedoma is thought to be among the most vulnerable to fire-induced thermokarst in the Arctic. With this dataset, we update observations on near-surface permafrost in the Anaktuvuk River tundra fire burn area from 2009 to 2023 using repeat airborne LiDAR-derived elevation data, ground temperature measurements, and cryostratigraphic studies. We have provided all of the data that has gone into an analysis and resulting paper that has been submitted for peer review at the journal Scientific Reports. The datasets include: - 1 m spatial resolution airborne LiDAR-derived digital terrain models from the summers of 2009, 2014, and 2021. - The area in which thaw subsidence was detected in the multi-temporal LiDAR data using the Geomorphic Change Detection software. - A terrain unit map developed for the 50 square kilometer study area. - Ground temperature time series measurements for a logger located in the burned area and a logger located in an unburned area. The ground temperature data consist of daily mean measurements at a depth of 0.15 m (active layer) and 1.00 m (permafrost) from July 2009 to August 2023. - Photos ~50 permafrost boreholes and the associated cores collected there. - A borehole log and notes pdf also accompanies our studies on the cryostratigraphy of permafrost post-fire and our observations on the recovery of permafrost. 

ABSTRACT The Yukon‐Kuskokwim Delta (YKD), covering ~75,000 km²of Alaska's discontinuous permafrost zone, has a historic (1902–2023) mean annual air temperature of ~−1°C and was previously thought to lack ice wedge networks. However, our recent investigations near Bethel, Alaska, revealed numerous near‐surface ice wedges. Using 20 cm resolution aerial orthoimagery from 2018, we identified ~50 linear km of ice wedge troughs in a 60 km²study area. Fieldwork in 2023 and 2024 confirmed ice wedges up to ~1.5 m wide and ~2.5 m in vertical extent, situated on average 0.9 m below the tundra surface (n = 29). Ground‐penetrating radar (GPR) detected additional ice wedges beyond those visible in the remote sensing imagery, suggesting an underestimation of their true abundance. Coring of polygonal centers revealed late‐Quaternary deposits, including thick early Holocene peat, late‐Pleistocene ice‐rich silts (reworked Yedoma), charcoal layers from tundra fires, and the Aniakchak CFE II tephra (~3600 cal yrs BP). Stable water isotopes from Bethel's wedge ice (mean δ¹⁸O = −15.7 ‰, δ²H = −113.1 ‰) indicate a relatively enriched signature compared to other Holocene ice wedges in Alaska, likely due to warmer temperatures and maritime influences. Expanding our mapping across the YKD using high‐resolution satellite imagery from 2012 to 2024, we estimate that the Holocene ice wedge zone encompasses ~30% of the YKD tundra region. Our findings demonstrate that ice wedge networks are more widespread across the YKD than previously recognized, emphasizing both the resilience and vulnerability of the region's warm, ice‐rich permafrost. These insights are crucial for understanding permafrost responses to climate change and assessing agricultural potential and development in the region. 

Permafrost-agroecosystems include all cultivation and pastoral activities in areas underlain by permafrost. These systems support local livelihoods and food production and are rarely considered in global agricultural studies but may become more relevant as climate change is increasing opportunities for food production in high latitude and mountainous areas. The exact locations and amount of agricultural production in areas containing permafrost are currently unknown, therefore we provide an overview of countries where both permafrost and agricultural activities are present. We highlight the socioecological diversity and complexities of permafrost-agroecosystems through seven case studies: (1) crop cultivation in Alaska, USA; (2) Indigenous food systems and crop cultivation in the Northwest Territories, Canada; (3) horse and cattle husbandry and Indigenous hay production in the Sakha Republic, Russia; (4) mobile pastoralism and husbandry in Mongolia; (5) yak pastoralism in the Central Himalaya, Nepal; (6) berry picking and reindeer herding in northern Fennoscandia; and (7) reindeer herding in northwest Russia. We discuss regional knowledge gaps associated with permafrost and make recommendations to policy makers and land users for adapting to changing permafrost environments. A better understanding of permafrost-agroecosystems is needed to help sustainably manage and develop these systems considering rapidly changing climate, environments, economies, and industries. 

Abstract. Climate change and increased fire are eroding theresilience of boreal forests. This is problematic because boreal vegetationand the cold soils underneath store approximately 30 % of all terrestrialcarbon. Society urgently needs projections of where, when, and why borealforests are likely to change. Permafrost (i.e., subsurface material thatremains frozen for at least 2 consecutive years) and the thicksoil-surface organic layers (SOLs) that insulate permafrost are importantcontrols of boreal forest dynamics and carbon cycling. However, both arerarely included in process-based vegetation models used to simulate futureecosystem trajectories. To address this challenge, we developed acomputationally efficient permafrost and SOL module named the Permafrost andOrganic LayEr module for Forest Models (POLE-FM) that operates at finespatial (1 ha) and temporal (daily) resolutions. The module mechanisticallysimulates daily changes in depth to permafrost, annual SOL accumulation, andtheir complex effects on boreal forest structure and functions. We coupledthe module to an established forest landscape model, iLand, and benchmarkedthe model in interior Alaska at spatial scales of stands (1 ha) tolandscapes (61 000 ha) and over temporal scales of days to centuries. Thecoupled model generated intra- and inter-annual patterns of snowaccumulation and active layer depth (portion of soil column that thawsthroughout the year) generally consistent with independent observations in17 instrumented forest stands. The model also represented the distributionof near-surface permafrost presence in a topographically complex landscape.We simulated 39.3 % of forested area in the landscape as underlain bypermafrost, compared to the estimated 33.4 % from the benchmarkingproduct. We further determined that the model could accurately simulate mossbiomass, SOL accumulation, fire activity, tree species composition, andstand structure at the landscape scale. Modular and flexible representationsof key biophysical processes that underpin 21st-century ecologicalchange are an essential next step in vegetation simulation to reduceuncertainty in future projections and to support innovative environmentaldecision-making. We show that coupling a new permafrost and SOL module to anexisting forest landscape model increases the model's utility for projectingforest futures at high latitudes. Process-based models that representrelevant dynamics will catalyze opportunities to address previouslyintractable questions about boreal forest resilience, biogeochemicalcycling, and feedbacks to regional and global climate. 

Abstract. As the northern high latitude permafrost zone experiences accelerated warming, permafrost has become vulnerable to widespread thaw. Simultaneously, wildfire activity across northern boreal forest and Arctic/subarctic tundra regions impact permafrost stability through the combustion of insulating organic matter, vegetation and post-fire changes in albedo. Efforts to synthesise the impacts of wildfire on permafrost are limited and are typically reliant on antecedent pre-fire conditions. To address this, we created the FireALT dataset by soliciting data contributions that included thaw depth measurements, site conditions, and fire event details with paired measurements at environmentally comparable burned and unburned sites. The solicitation resulted in 52,466 thaw depth measurements from 18 contributors across North America and Russia. Because thaw depths were taken at various times throughout the thawing season, we also estimated end of season active layer thickness (ALT) for each measurement using a modified version of the Stefan equation. Here, we describe our methods for collecting and quality checking the data, estimating ALT, the data structure, strengths and limitations, and future research opportunities. The final dataset includes 47,952 ALT estimates (27,747 burned, 20,205 unburned) with 32 attributes. There are 193 unique paired burned/unburned sites spread across 12 ecozones that span Canada, Russia, and the United States. The data span fire events from 1900 to 2022. Time since fire ranges from zero to 114 years. The FireALT dataset addresses a key challenge: the ability to assess impacts of wildfire on ALT when measurements are taken at various times throughout the thaw season depending on the time of field campaigns (typically June through August) by estimating ALT at the end of season maximum. This dataset can be used to address understudied research areas particularly algorithm development, calibration, and validation for evolving process-based models as well as extrapolating across space and time, which could elucidate permafrost-wildfire interactions under accelerated warming across the high northern latitude permafrost zone. The FireALT dataset is available through the Arctic Data Center. 

Abstract Beavers were not previously recognized as an Arctic species, and their engineering in the tundra is considered negligible. Recent findings suggest that beavers have moved into Arctic tundra regions and are controlling surface water dynamics, which strongly influence permafrost and landscape stability. Here we use 70 years of satellite images and aerial photography to show the scale and magnitude of northwestward beaver expansion in Alaska, indicated by the construction of over 10,000 beaver ponds in the Arctic tundra. The number of beaver ponds doubled in most areas between ~ 2003 and ~ 2017. Earlier stages of beaver engineering are evident in ~ 1980 imagery, and there is no evidence of beaver engineering in ~ 1952 imagery, consistent with observations from Indigenous communities describing the influx of beavers over the period. Rapidly expanding beaver engineering has created a tundra disturbance regime that appears to be thawing permafrost and exacerbating the effects of climate change.