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In recent decades, beavers have extended their range from the boreal forest into the Arctic tundra, altering tundra streams and surrounding permafrost at local to regional scales. In lower latitudes, beaver damming can convert streams, backwaters, and lake outlets into connected ponds, which in turn can change the course of channels, temperature of streams, sediment loads, energy exchange, aquatic habitat diversity and nutrient cycling, and riparian vegetation. In the Arctic, effects of beavers may include enhanced thawing of permafrost, increased stream temperatures, and changes in seasonal ice in streams, as well as complex ecosystem responses. This study will 1) document movement of beavers from the forest into tundra regions, 2) understand how stream engineering wrought by beavers will change the arctic tundra landscape and streams, and 3) predict how beavers will expand into tundra regions and alter stream and adjacent ecosystems. Results will be of interest to local communities and resource managers, and the team of investigators will convene a scientist and stakeholder workshop in Fairbanks, Alaska to synthesize observations, compare results from studies in temperate ecosystems, and clarify impacts of beaver expansion unique to the tundra biome. In April 2024 we used a ground penetrating radar (GPR) to image the subsurface surrounding beaver ponds in a tundra region near Kotzebue, Alaska. We used a Mala GX GPR (Mala Ground Explorer GPR) with a 450 megahertz (mhz) antenna and an integrated DGPS (differential global positioning system). GPS (global positioning system) location data is stored in the .cor file. 

### Access Data files can be accessed and downloaded from the directory via: [https://arcticdata.io/data/10.18739/A2M03Z00G](https://arcticdata.io/data/10.18739/A2M03Z00G) ### Overview Emergence of beavers as ecosystem engineers in the New Arctic project focuses on establishing field sites at tundra beaver ponds to study the implications of beaver engineering on ecosystems. We established three game camera sites at beaver-impacted streams on the Baldwin Peninsula from August 2023-April 2024. We aimed to collect information regarding ice formation phenology, overflow dynamics, and wildlife interactions. Two cameras were deployed adjacent to beaver dams, and another was deployed at a "control" site in a part of a stream that remains unimpacted by beavers. Cameras were set in a hybrid setting, collecting images through timelapse and trigger settings. Two cameras (Moultrie brand) lost power in early December, and one (Bushnell brand) maintained power over the entire study period. Cameras captured ice formation dynamics in early fall, as well as a series of overflow events. From this rudimentary data set, we did not detect differences in ice formation between ponds and the control site. We were also able to detect a dam bursting event following an August rain storm, which beavers did not repair before winter. Cameras captured a variety of wildlife, including red foxes, moose, brown bears, Canada geese, green-winged teal, and, of course, beavers. 

Abstract Beavers (Castor canadensis) are rapidly colonizing the North American Arctic, transforming aquatic and riparian tundra ecosystems. Arctic tundra may respond differently than temperate regions to beaver engineering due to the presence of permafrost and the paucity of unfrozen water during winter. Here, we provide a detailed investigation of 11 beaver pond complexes across a climatic gradient in Arctic Alaska, addressing questions about the permafrost setting surrounding ponds, the influence of groundwater inputs on beaver colonization and resulting ponds, and the change in surface water and aquatic overwintering habitat. Using field measurements, in situ dataloggers, and remote sensing, we evaluate permafrost, water quality, pond ice phenology, and physical characteristics of impoundments, and place our findings in the context of pond age, local climate, permafrost setting, and the presence of perennial groundwater inputs. We show beavers are accelerating the effects of climate change by thawing permafrost adjacent to ponds and increasing liquid water during winter. Beavers often exploited perennial springs in discontinuous permafrost, and summertime water temperatures at spring‐fed (SF) beaver ponds were roughly 5°C lower than sites lacking springs (NS). Late winter liquid water was generally present at pond complexes, although liquid water below seasonal ice cover was shallow (5–82 cm at SF and 5–15 cm at NS ponds) and ice was thick (median: 85 cm). Water was less acidic at SF than NS sites and had higher specific conductance and more dissolved oxygen. We estimated 2.4 dams/km of stream at sites on the recently colonized (last ~10 years) Baldwin Peninsula and 7.4 dams/km on the Seward Peninsula, where beavers have been present longer (~20+ years) and groundwater‐surface water connectivity is more common. Our study highlights the importance of climatic and physiographic context, especially permafrost presence and groundwater inputs, in determining the characteristics of the Arctic beaver pond environment. As beavers continue their expansion into tundra regions, these characteristics will increasingly represent the future of aquatic and riparian Arctic ecosystems. 

This dataset contains permafrost thaw depth measurements at Alaskan beaver ponds collected as part of the Arctic Beaver Observation Network and NSF ANS #1850578. The Arctic Beaver Observation Network is a 5-year project (2021-2026) funded by the National Science Foundation. The natural science part of the project uses remote sensing to observe the progress and impacts of beaver engineering in the Arctic, starting in Alaska and extending into Canada and Eurasia. The project also establishes field sites at tundra beaver ponds to study the implications of beaver engineering on hydrology and permafrost, as well as pond evolution documented using Unmanned Aerial Systems (UAS). Remote sensing work will map beaver ponds over time. Field measurements at tundra beaver ponds are made in August and late March. Data generated by field measurements include water level and temperature from pressure-transducers, subsurface imaging from ground-penetrating radar, sonar measurements for beaver pond bathymetry, tabular data associated with water quality measurements, and ice thickness and water depth (in winter). Data is also posted from UAS surveys: annual visible and multi-spectral surveys, as well as snow depth. This dataset comprises thaw depth measurements along transects near beaver ponds, to document permafrost impacts over time. 

This dataset contains water level, water temperature, and barometric pressure at Alaskan beaver ponds collected as part of the Arctic Beaver Observation Network and NSF ANS #1850578. The Arctic Beaver Observation Network is a 5-year project (2021-2026) funded by the National Science Foundation. The natural science part of the project uses remote sensing to observe the progress and impacts of beaver engineering in the Arctic, starting in Alaska and extending into Canada and Eurasia. The project also establishes field sites at tundra beaver ponds to study the implications of beaver engineering on hydrology and permafrost, as well as pond evolution documented using Unmanned Aerial Systems (UAS). Remote sensing work will map beaver ponds over time. Field measurements at tundra beaver ponds are made in August and late March. Data generated by field measurements include water level and temperature from pressure-transducers, subsurface imaging from ground-penetrating radar, sonar measurements for beaver pond bathymetry, tabular data associated with water quality measurements, and ice thickness and water depth (in winter). Data is also posted from UAS surveys: annual visible and multi-spectral surveys, as well as snow depth. 

Burrowing species rely on subterranean and subnivean sites to fulfill important life-history and behavioral processes, including predator avoidance, thermoregulation, resting, and reproduction. For these species, burrow architecture can affect the quality and success of such processes, since characteristics like tunnel width and chamber depth influence access by predators, thermal insulation, and energy spent digging. Wolverines (Gulo gulo) living in Arctic tundra environments dig burrows in snow during winter for resting sites and reproductive dens, but there are few published descriptions of such burrows. We visited 114 resting burrows and describe associated architectural characteristics and non-snow structure. Additionally, we describe characteristics of 15 reproductive den sites that we visited during winter and summer. Although many resting burrows were solely excavated in snow, most incorporated terrain structures including cliffs, talus, river shelf ice, thermokarst caves, and stream cutbanks. Burrows typically consisted of a single tunnel leading to a single chamber, though some burrows had multiple entrances, branching tunnels, or both. Tunnels in resting burrows were shorter than those in reproductive dens, and resting chambers were typically located at the deepest part of the burrow. Reproductive dens were associated with snowdrift-forming terrain features such as streambeds, cutbanks on lake edges, thermokarst caves, and boulders. Understanding such characteristics of Arctic wolverine resting and reproductive structures is critical for assessing anthropogenic impacts as snowpack undergoes climate-driven shifts.