Environmental Impacts from Projected Permafrost Thaw in Alaska: Defining Knowledge Gaps, Data Needs, and Research Priorities

Abstract

Thawing permafrost will significantly impact regulatory activities in Alaska that are conducted by the U.S. Environmental Protection Agency (EPA) to protect human health and the environment. Many of those activities are in vulnerable rural lands predominantly occupied by Alaska Natives. Temperatures in Alaska—the largest and northernmost of the 50 states—are increasing disproportionately relative to the global average and at a markedly higher rate than in any other state in the Nation. Most land and surface waters in Alaska are underlaid by permafrost (or perennially frozen ground), which stabilizes infrastructure, serves community needs, and shapes ecosystems with unique environmental characteristics. The Fourth National Climate Assessment estimated that 16–24% of near-surface Alaskan permafrost could disappear by the end of this century. Permafrost thaw not only compromises critical infrastructure used in daily life (e.g., buildings, roads, and pipelines), but also alters movement of hazardous substances within the surrounding environment. Changes to permafrost characteristics and extent may release contaminants through multiple mechanisms which can pollute air, soil, and water, with unintended consequences to subsistence activities and the livelihood of local communities. This paper summarizes information gathered from semi-formal interviews conducted with EPA regulatory staff during late 2022 to glean the breadth of activities that would be affected by permafrost thaw, tabulate available data sources, and identify data and knowledge gaps. This information can be used to influence monitoring activities and future research that can inform EPA regulatory activities affected by permafrost thaw in Alaska.

1. Introduction

Permafrost includes water, soil, rock, or sediment that is persistently frozen for at least two years. Permafrost is observed at polar latitudes and at high altitudes, and it is most widespread in the United States within Alaska. Nearly a quarter of exposed land in the Northern Hemisphere is atop a permafrost layer (Biskaborn et al. 2019; Jin et al. 2021), which can extend hundreds of meters below the earth’s surface. Permafrost is “continuous” if the area is large and uninterrupted below the surface or “discontinuous” if it contains some ground areas that are not completely frozen in the coldest months. Discontinuous permafrost occurs in the transition latitudes and altitudes and when continuous permafrost diminishes over time.

Permafrost offers value to society because of its cold, solid, and typically stable characteristics. Disproportionate warming in northern latitudes, however, has led to rapid permafrost thaw and erosion in Alaska (e.g., Wang et al. 2018) that adversely impacts those values. According to Huntington et al. (2023), thawing permafrost in Alaska has been “transforming ecosystems, disrupting cultural practices, harming fisheries and other livelihoods, exacerbating health disparities, and placing infrastructure at risk.” At the precipice of permafrost thaw in the Arctic are eight remote Alaska Native villages in the North Slope Borough (NSB) of Alaska. These villages and their peoples rely on permafrost to provide in-ground refrigeration for critical subsistence foods, like whale meat and blubber. In the NSB, permafrost maintains near-surface liquid water availability and surface streamflow that supports aquatic habitats for fish and wildlife. Similarly, downstream coastal estuaries fed by streams and rivers atop permafrost support aquatic invertebrates, fish, migratory birds, whales, and mammals that are sources of subsistence; permafrost thaw can increase the connectivity between groundwater and these surface waters. Permafrost has cultural significance for Alaska Natives. It also stores carbon, nutrients, and contaminants that can harm people, ecosystems, and species that live in them.

Permafrost is vulnerable to thaw and erosion under rapid and persistent warming, jeopardizing its roles to society and the environment. In 2008, permafrost underlaid ~85% of the land in Alaska (Jorgenson et al. 2016; Alaska DGGS 2023b). However, average near-surface air temperatures have been increasing in the Arctic over the past four decades, leading to increases in permafrost temperature and permafrost thaw. The annual air temperatures in the Arctic in 2014–2018 exceeded every prior year since 1900, and temperatures in two of those years were >6°C above the 30-year climatological average (Meredith et al. 2019). Mean annual air temperatures for 2014–2019 at Alaskan National Parks at high altitude and along the northern shores were 2°C and 3°C warmer than climatology compared to a 1°C anomaly elsewhere in Alaska, yielding widespread permafrost thaw (Swanson et al. 2020). During 2007–2016, permafrost temperatures increased by 0.39°C ±0.15°C across continuous Arctic monitoring sites (Biskaborn et al. 2019). Concurrently, permafrost temperatures in Alaska have been increasing at 0.6°F (0.33°C) per decade (U.S. EPA, 2024). Nearly all studies project that the near-surface permafrost extent in the Northern Hemisphere will be reduced at 2100 compared to pre-industrial conditions, but they vary widely in the severity of loss from 14% (Peng et al. 2023) to 93% (Guo et al. 2023) across the Northern Hemisphere, and locally up to 92% in Alaska’s Seward Peninsula (Debolskiy et al. 2020). Though the projected extent of permafrost loss is inharmonious, small overall losses would still produce significant and dramatic effects at regional and local scales. Therefore, communities in NSB necessitate monitoring and protection to minimize the potentially significant adverse effects of permafrost thaw.

The increased air and permafrost temperatures will yield widespread increases in formation and depth of taliks—subsurface unfrozen ground that lies in permafrost—especially in forested areas and near warmer ecosystems (Farquharson et al. 2022). Thawing permafrost can release a reservoir of previously frozen and trapped carbon as carbon dioxide and methane into the atmosphere, which could contribute to further warming on a global scale (Schuur et al. 2015). Thawing permafrost can initiate profound environmental changes by compromising the isolated ecosystems that allow plant and animal species, and even microbial communities, to thrive.

Thawing permafrost is rapidly destabilizing Alaskan community and industrial infrastructure (Markon et al. 2018; Huntington et al. 2023). Permafrost serves as a terra firma into which physical supports for the Trans-Alaska Pipeline System (TAPS) have been drilled to transport oil from Alaska’s North Slope to market. Thawing permafrost creates vulnerabilities from movement and settling of the ground, significantly impacting infrastructure by destabilizing the ground on which homes, roads, public utilities, and industrial sites are built (e.g., von Deimling et al. 2021). Hjort et al. (2022) suggest that 30–50% of Arctic infrastructure could be at risk from permafrost thaw by 2050. At the northernmost extent of the TAPS and the primitive trucking road to the Arctic Ocean is Deadhorse, an unincorporated community within the NSB that is utilized to support oil production and housing workers for the nearby Prudhoe Bay Oil Field. Within the NSB, Deadhorse recently experienced the highest rate of temperature increase at 1.5°F (0.83°C) per decade (U.S. EPA, 2024). This increase in temperature has accelerated local permafrost thaw, increasing structural risks for the TAPS. In addition, thaw at a proposed hazardous waste facility in Deadhorse could unexpectedly release hazardous waste, which can bioaccumulate on local fauna (Hoover et al., 2012) and could create contaminant seepage into nearby Prudhoe Bay. Coastal erosion would exacerbate subsidence and settling caused by permafrost thaw, further compromising existing infrastructure and ecosystems.

Industries have historically used permafrost in remote regions for disposal of toxic, radioactive, and industrial wastes, assuming the permafrost “containment” would curtail the environmental impacts of those substances (Langer et al. 2023). Permafrost may restrict groundwater movement to neighboring soils and aquifers that provide public water use, minimizing contamination. In continuous areas, permafrost creates a natural barrier from contaminant migration into deeper aquifer soils and sediments; in these systems, however, water used for drinking or other public use typically is drawn from surface water features instead of groundwater. In that case, permafrost sometimes creates a conduit for landfill contaminants to migrate into public water systems via surface transport. Permafrost thaw near these landfills increases the risks of contamination to downstream drinking water sources.

Permafrost thaw impacts numerous regulatory programs in Alaska within U.S. Environmental Protection Agency (EPA) Region 10 (R10), which lacks access to comprehensive permafrost data. Models infer permafrost extent from temperature, depth, mineralogy, and/or seasonal freeze/thaw cycles, often resulting in inconsistent determinations for the same area. Managing environmental risks attributed to permafrost thaw requires considering multiple models and datasets concurrently. Without comprehensive and localized permafrost-related knowledge, data, and projections of changes for Alaska, regulators may inadvertently neglect consequences of permafrost thaw. Remediation of corrective action sites¹ strives to make the land useful for the surrounding communities. Comprehensively assessing the risks of permafrost thaw in Alaska requires considering the impacts to Tribal subsistence and way-of-life practices.

This paper is the outcome of an internal study at EPA conducted in late 2022, where staff were interviewed about their permafrost data and informational needs to support regulatory activities and actions throughout Alaska and which are under the purview of EPA. The interviewees were primarily regulatory staff who have environmental stewardship roles in Alaska. The interviewees were queried on their activities in Alaska, their knowledge of relevant data and informational sources, and their data needs to perform duties more effectively while considering uncertainties associated with permafrost thaw. The information gathered in these interviews presents the breadth of publicly accessible data from federal, state, local, Tribal, and international entities. The interviews also captured factors related to permafrost thaw (e.g., industrial infrastructure built near the coasts is impacted by permafrost thaw, sea level rise, and coastal erosion, which collectively inform regulatory strategies). More importantly, these semi-structured interviews identified data and knowledge gaps that could be used to shape EPA research priorities. Generally, EPA’s interests can be scoped to issues directly impacting Alaska Native villages (e.g., landfills and subsistence), infrastructure (e.g., industrial activities, hazardous waste, and resource development), and environment (e.g., impacts on drinking water, ecosystem dynamics, and ecological properties).

2. Geography and Population of Alaska

Alaska is the largest state in the United States, with a land area >1,700,000 km² encompassing 18% of the Nation’s landmass. Alaska has more than twice as much land area as the next largest state. Alaska is the northernmost state, with considerable landmass north of the Arctic Circle. Alaska boasts the longest coastline of any state, and it holds more than 50% of the total U.S. coastline. The topography ranges from sea level to the highest peak in the U.S. at 6190 meters above sea level.

Although Alaska is the largest state, it has one of the smallest populations, at under 740,000 people, ~40% of whom live in Anchorage (Alaska DOLWD 2020). Alaska has a population that is 65% White, 16% Alaska Native (Tribal), 7% Asian, 4% Black, 1% Pacific Islander, and 8% multiracial (Alaska DOLWD 2020). The Tribal population in Alaska proportionally exceeds that of any other state in the U.S. Most of the rural population resides in towns, villages, and clustered settlements, often surrounded by uninhabited land. According to the Bureau of Indian Affairs, there are 227 unique Alaska Native villages and 229 Federally Recognized Tribes². Alaska Natives are the majority population in the northern and northwestern regions of the state (Fig. 1). The NSB sits north of the Arctic Circle and is home to ~10,000 residents. NSB encompasses 240,000 km² and borders the Arctic Ocean, setting it at the forefront of environmental changes from widespread warming.

Figure 1.

Proportion of Alaska Native population in relation to the total population by borough and Census area, 2019. (Figure 2.6 from Alaska DOLWD 2020)

3. Permafrost Influences on Regulatory and Tribal Actions

Semi-structured interviews were conducted primarily with staff in R10, which serves the states of Alaska, Washington, Oregon, and Idaho. Interviews were only conducted with staff whose work was related to environmental actions in Alaska. Interviews were conducted in late 2022 and summarized in an internal report in January 2023. Interviewees were hand-selected based on subject matter expertise, and there was no requirement to accept the interviews. The questions were designed to elucidate the environmental issues related to permafrost and data needs. Specifically, subject matter experts were asked to describe how they would use permafrost data and future permafrost condition data in their work, what data and information they already can access, and existing gaps in their data and information. The text, below, reflects the responses to the survey but should not be interpreted as prescriptive of EPA policy.

a. RCRA Corrective Action and PCB Cleanups

EPA manages corrective actions (e.g., cleanups) of hazardous wastes under both Resource Conservation and Recovery Act (RCRA) and Toxic Substances Control Act (TSCA), including many sites across Alaska (Fig. 2). Cleanups under TSCA include identifying, evaluating, and mitigating contaminants, like perchlorinated biphenyls (PCBs³), found in soil, groundwater, surface water, and air. In the cleanup process, facility owners/operators conduct site characterizations and risk assessments that prompt remedial options. The remedies selected for each site consider risks, intended uses of the site, and technical practicability of potential remedies. Remedies are intended to achieve clean closure of each site.

Figure 2.

Active RCRA (left) and PCB (right) sites in Alaska. Exported from https://rcraquery.epa.gov/metabase (September 2022).

Many EPA corrective action facilities have a 10–30-year window for closure and the associated remedies, but some cleanups in Alaska could last for 40–50 years. Sporadically, Alaskan cleanups are indefinite because certain contaminants persist in the environmental conditions.

Most Alaskan cleanup sites are in areas with permafrost. Site remedies that consider future changes in permafrost conditions could mitigate additional hazardous waste releases. Scenarios of future permafrost conditions could influence siting facilities to hold, manage, and/or dispose of hazardous waste in the Arctic over different timelines. Where permafrost is present, RCRA and PCB site managers consider:

• Damage to infrastructure. Thawing permafrost and subsidence can damage pipelines, oil well cellars, hazardous waste storage units, and buildings. Current best management strategies (e.g., placing buildings on pillars set into the permafrost with thermosiphons to prevent the pillars from warming the ground around them) are insufficient when there is substantial permafrost thaw. Damaged infrastructure could also significantly increase the number of cleanup sites. For example, multiple PCB cleanups along major pipelines in Alaska could be compromised by thawing permafrost, resulting in new hazardous waste releases from damaged pipelines.

• Fate and transport of contaminants. Permafrost currently constrains the movement of contaminants from some unlined landfills. Thawing permafrost could promote greater seepage to surface waters, groundwater, and thawed soils. Through multiple pathways, water from thawed permafrost can chemically transform contaminants into new toxic substances. Additionally, warmer soils can volatilize and release contaminants into the air.

• Land, surface water, and ecosystem changes. As permafrost thaws and land subsides, new ponds and lakes can form, surface and groundwater can be routed to new areas and take on new paths, and ecosystem properties and functions can be altered, changing the recommended remedies intended to protect and preserve these ecosystems over time.

• Impacts to groundwater. Permafrost thaw can change the amount and direction of groundwater flow. Monitoring wells are typically sited to measure existing groundwater flow characteristics, but changes to flow associated with thawing permafrost may require a different spatial distribution of monitoring wells.

• Human habitation. Alaska Native communities may choose to utilize remediated oil and gas sites (i.e., gravel pads/gravel), as sites or road materials to support community infrastructure needs in “gravel-poor” areas. Permafrost thaw can render these sites unstable.

• Alaska Native impacts: Alaska Native communities in the Arctic store meat and blubber from harvested marine mammals in the permafrost, and contaminant releases could render their traditional foods unsafe for consumption. Drinking water and subsistence fish can be exposed to contaminants as their migration increases with permafrost thaw.

To address these issues, EPA RCRA and PCB site managers desire a tool that includes current permafrost conditions and future permafrost projections statewide to better understand consequences of permafrost thaw and whether existing remedies are adaptable and appropriate. Specifically:

• Permafrost conditions with sufficient resolution to evaluate conditions at hazardous waste sites (typically ~1000–2000 m²). For larger sites, the resolution must be sufficient to understand whether conditions vary across the site (e.g., one of EPA’s largest sites to analyze is estimated to be >970 km²). Cleanup sites occur throughout Alaska, so the data should encompass all areas within the state that contain permafrost.

• Future permafrost conditions for near-term (at 2040) and longer-term (at 2070) periods. If possible, there was a strong desire for higher time-resolved projections (e.g., decadal increments through 2100).

• Permafrost conditions and impacts under multiple future emissions scenarios, including:

  • Spatial distribution of continuous vs. discontinuous permafrost.
  • Depth to continuous and discontinuous permafrost.
  • Change in permafrost depth/distribution (i.e., the change from present/baseline conditions).
  • Permafrost temperature (i.e., mean annual ground temperature).
  • Impact of thawed permafrost on:

    • Surface waters (location, depth, flow characteristics, quantity, and drainage)
    • Groundwater (quantity, flow rate, and direction), and
    • Land (areas of subsidence, including the presence and development of thermokarst).

• Vulnerabilities to massive ice bodies (i.e., surface ice wedges) in permafrost that could signal differential thaw/settlement compared to other permafrost constituents (such as rock and soil) to compare solutions at cleanup sites.

• Impacts of permafrost thaw on subsidence, surface water bodies, and groundwater flows.

RCRA and PCB site managers also want current data and future projections at their sites in Alaska, including:

• Sea level rise

• Heavy precipitation, which creates landslides and debris flows

• Vegetation/land cover changes, including those from drought

• Wildfire risk, including changes due to permafrost thaw

• Coastal erosion, which is directly tied to permafrost thaw along northern coastlines

• Air temperature

b. Infrastructure and Health Impacts in Rural Alaskan and Tribal Communities

Thawing permafrost is affecting rural Alaskan and Tribal communities. Many communities rely on surface water bodies for their drinking water, but thawing permafrost can change hydrologic flows and potentially eliminate or contaminate drinking water sources. Community infrastructure can be damaged by thawing permafrost, including homes that have been built on pilings driven into the permafrost and ice cellars used to store food. Homes damaged by permafrost thaw are susceptible to water infiltration and mold growth, leading to unhealthy indoor air quality. Additionally, waste infrastructure (such as wastewater lagoons and landfills) can be impacted by permafrost thaw, potentially mobilizing contaminants that would otherwise be contained.

Solid waste collected in rural Alaskan communities is often comingled with hazardous household waste and electronic waste in Class III landfills⁴. In Alaska, Class III landfills do not have a geotechnical liner, and they cannot be retroactively lined. In parts of Alaska, continuous permafrost restricts the movement of contaminants, but permafrost thaw could allow contaminants from the landfill to enter the surrounding land and water resources. As of April 2024, there are 184 Class III landfills in Alaska⁵, and many of the older landfills are experiencing erosion due to natural processes (e.g., precipitation and seasonal thaw cycling) that can instigate the release of contaminants. Thawing permafrost could accelerate release of contaminants from some landfills. Siting and management of landfills in Tribal communities can involve many parties, partially because of the promulgation of the Alaska Native Claims Settlement Act. Therefore, city governments and regional/city corporations may own or manage the land where landfills are located.

Damage from permafrost thaw—in conjunction with other factors, such as rising sea levels and coastal erosion—has already caused some Alaska Native Tribes to relocate, and more Tribes may consider relocation in the future. As part of the relocation discussions, EPA staff advise stakeholders on impacts to indoor air quality, drinking water, wastewater, and human health. Internal EPA research is anticipating contaminant movement through unlined Class III landfills, developing conceptual models of human exposure (including via ingestion of subsistence foods and drinking water collected from traditional sources), and monitoring contaminant fate and transport through sampling that began in 2023. EPA staff have been conducting outreach to Alaska Native Tribes to identify collaborators for this work.

To that end, EPA staff requested data and a tool that can be used internally and shared with external stakeholders to support decision-making related to permafrost impacts.

Ideally, this tool would include:

• GIS layers for current and projected future permafrost conditions at a resolution suitable for evaluating impacts to landfills and community infrastructure. These permafrost GIS layers would delineate current and future areas of continuous and discontinuous permafrost and the estimated depth of permafrost. Data would represent a range of future periods under different scenarios.

• GIS layers focused on other community planning needs (e.g., locations of current homes and infrastructure, drinking water protection zones). Some of these data may be available from Alaska Department of Environmental Conservation (ADEC) and other stakeholders but would be more useful if combined with permafrost projections. During the 2022 interviews, EPA staff identified several publicly available GIS layers that could be useful to overlay with permafrost projections (see Table 1).

Table 1.

Tools identified in Fall and Winter 2022 that include historical and future data that could be useful for understanding impacts of permafrost thaw on environmental issues in Alaska.

Tool/Resource	Description
UAF-SNAP Community Permafrost Data Tool	University of Alaska Fairbanks Scenarios Network for Alaska + Arctic Planning (UAF-SNAP) tool with information on permafrost risks for rural Alaska communities based on measured data. https://www.snap.uaf.edu/tools/permafrost
UAF-SNAP Northern Climate Reports (beta tool)	UAF-SNAP tool with scenario projections for Alaska (i.e., temperature, precipitation, permafrost extent, ground temperature, wildfire flammability, vegetation type). Watersheds/communities can be searched by name or location. https://northernclimatereports.org/
UAF Permafrost Laboratory	University of Alaska Fairbanks permafrost research group page, which includes datasets, maps, and publications. https://permafrost.gi.alaska.edu/
Climate Change Indicators: Permafrost	EPA website summarizing trends in permafrost borehole temperature measurements in Alaska. https://www.epa.gov/climate-indicators/climate-change-indicators-permafrost
Interstate Technology Regulatory Council: Permafrost Thaw	Sustainable best management practices addressing permafrost thaw at remediation sites. Developed by the Interstate Technology Regulatory Council, a state-led environmental coalition. https://srr-1.itrcweb.org/key-sustainable-best-management-practices-for-sustainable-resilience-to-extreme-weather-events-and-wildfires/#7_12
Indigenous Observation Network: Permafrost Monitoring Project	Permafrost measurements collected since 2009 by the Indigenous Observation Network, a U.S. Geological Survey and Yukon River Inter-Tribal Watershed Council collaboration. https://www.citizenscience.gov/catalog/18/
NREL Cold Climate Housing Research Center	The National Renewable Energy Laboratory (NREL) Cold Climate Housing Research Center partnership with the U.S. Army Cold Regions Research and Engineering Laboratory to study permafrost soils and optimal foundation designs. http://cchrc.org/permafrost-foundations-2/
U.S. Army Cold Regions Research and Engineering Laboratory	Information on the U.S. Army Corps of Engineers research center initiatives, including the permafrost research tunnel. https://www.erdc.usace.army.mil/Locations/CRREL/
Multi-Resolution Land Characteristics Consortium	Consistent historical and current landcover data for the entire country, produced by a consortium of federal agencies. https://www.mrlc.gov/
Statewide Threat Assessment	Report prepared in 2019 for the Denali Commission on permafrost and other threats to remote Alaskan communities. https://www.denali.gov/wp-content/uploads/2019/11/Statewide-Threat-Assessment-Final-Report-20-November-2019.pdf
High-Resolution Permafrost Modeling in Denali National Park and Preserve	University of Alaska-Fairbanks research publication focused on high-resolution modeling in Denali. https://permafrost.gi.alaska.edu/sites/default/files/High-resolution%20permafrost%20modeling%20in%20DENA.pdf
Northern Alaska Landscape/Permafrost GIS Files	The U.S. Fish and Wildlife Service manages Landscape Conservation Cooperative Networks, including a network for northern Alaska that collates permafrost GIS data.9 https://lccnetwork.org/resource/northern-alaska-landscapepermafrost-gis-files
Permafrost Soils Database for Northern Alaska	The U.S. Fish and Wildlife Service manages Landscape Conservation Cooperative Networks, including a network for northern Alaska that collates soils data. https://lccnetwork.org/resource/permafrost-soils-database-northern-alaska
Permafrost Characteristics of Alaska(2008 Shapefile)	University of Alaska Fairbanks produced this GIS permafrost map of Alaska in conjunction with the Ninth International Conference on Permafrost https://catalog.northslopescience.org/dataset/1725
Permafrost Map of Alaska, USA, Version 1	National Snow and Ice Data Center (University of Colorado Boulder) permafrost map of Alaska at a scale of 1:2,500,000. https://nsidc.org/data/ggd320/versions/1
IARPC Permafrost Collaboration Team	Interagency Arctic Research Policy Committee permafrost collaboration team, which holds regular meetings with presentations from experts. https://www.iarpccollaborations.org/index.html
IARPC Arctic Research Plan 2022–2026	Interagency Arctic Research Policy Committee’s current Arctic research plan. https://www.iarpccollaborations.org/plan/index.html
IARPC Biennial Implementation Plan 2022–2024	Interagency Arctic Research Policy Committee’s current biennial research plan. https://www.iarpccollaborations.org/uploads/cms/documents/2022-2024%20BIP%20FINAL%20High%20Res%2020221109.pdf
State of Alaska DNR: Permafrost and Periglacial Hazards	Information on Alaska Department of Natural Resources permafrost research projects. https://dggs.alaska.gov/hazards/permafrost.html
Using Thermistors to Measure Permafrost Integrity	Research publication from the U.S. Geological Survey led by an expert in permafrost temperature measurements who served as a consultant to EPA on the Fort Wainwright NPL site. https://essd.copernicus.org/articles/6/201/2014/essd-6-201-2014.pdf

In addition, information would be required on how the EPA and external stakeholders (e.g., state agencies and Tribal community members) could use such a tool for decision-making. For example, Tribal communities will need to understand the likelihood and timing of the permafrost changes and their impacts on the community infrastructure.

More broadly, EPA and its partners could leverage the best-available technologies to preserve permafrost and/or counteract thaw. For example, thermosiphons could be used to maintain temperatures in permafrost that is used for ice cellars and permafrost around pilings, but there may be other viable technologies to consider or to be developed.

c. National Priorities List

EPA manages two National Priorities List⁶ (NPL) sites where permafrost is present: Fort Wainwright and Eielson AFB, both near Fairbanks. Fort Wainwright is ~3600 km² within an active military installation on the eastern boundary of Fairbanks. Fort Wainwright contains numerous areas in which EPA and external agencies manage contaminants, including Comprehensive Environmental Response, Compensation and Liability Act (CERCLA, i.e., “Superfund”) Operable Units, state-managed sites (mostly ineligible under CERCLA), and munition sites. Fort Wainwright has ~15,000 residents who access drinking water from wells near contaminated grounds. The Chena River traverses the contaminated part of Fort Wainwright, and the river provides residents with subsistence, recreation, and sport fishing. The portion of the site north of the river contains discontinuous permafrost.

Permafrost thaw can impact remedies at this site. For example, at Fort Wainwright, a permafrost thaw channel created a preferential pathway for a benzene plume that breached the community water system. Although benzene concentrations have been reduced to cleanup thresholds, environmental concerns remain at other sites within Fort Wainwright, where deforestation, using the land as a snow dump, and potential future permafrost thaw could collectively introduce contaminants into the local water system. Additionally, a site at Fort Wainwright is currently surrounded by discontinuous permafrost; while the permafrost is not part of the site remedy, permafrost thaw could change the hydrology surrounding the landfill and initiate mobilization of contaminants. Furthermore, permafrost thaw could change the remedies selected for these sites, as the combination of low permeability soils, permafrost thaw, and the existing thaw bulb⁷ under roads could hinder remediation and monitoring conditions.

Groundwater monitoring wells measure concentrations of contaminants of concern. Monitoring wells in discontinuous permafrost at Fort Wainwright are set at three depths: shallow (above permafrost), intermediate (within the discontinuous permafrost, i.e., ~18–24 meters), and deep (below the permafrost, i.e., >36 meters). Seasonally active permafrost can interfere with monitoring wells through “frost jacking”, where the wells are pushed out of the ground or cracked during freeze/thaw cycles. Understanding predicted changes to the depth of seasonal thaw could mitigate impacts to monitoring wells.

A major concern for the Fort Wainwright site is that thawing permafrost could change hydrology, mobilize contaminants, and facilitate chemical reactions that produce new site contaminants (e.g., methylmercury produced from inorganic mercury already present at the site). The U.S. Army Corps of Engineers has collected data on permafrost integrity at Fort Wainwright using tools such as ground-penetrating radar and thermistors placed in monitoring wells. The current permafrost data are approximately a decade old, but updates have been planned that may include a site permafrost model (Wagner et al. 2024). Additionally, EPA would like information on expected changes to permafrost on the site so that monitoring wells can be sited in advance of these changes.

EPA staff requested high-resolution data on future permafrost conditions at the Fort Wainwright NPL site, including:

• Data showing a range of likely conditions over the next 30 years (the current remediation timeline) and beyond (in case of extensions to that timeline). Preferably, there would be regularly spaced projections (e.g., every 10 years) so that changes can be evaluated and accommodated over time.

• Extent of discontinuous permafrost, depth of seasonal (summer) thaw, and depth of permafrost.

• Data with timelines and locations of complete permafrost thaw, which could alter site hydrology and elevated groundwater that may mobilize soil contaminants.

• Data at sufficient resolution to evaluate permafrost changes impacting specific areas of the site.

• Data in a format that is easily shared with other stakeholders.

Further, these activities may leverage new research related to contaminants and permafrost thaw, such as the transfer of toxic per- and polyfluoroalkyl substances (PFAS) between soil, ice, and air.

d. Emergency Response and Oil Spill Prevention

EPA provides emergency response to oil discharges that threaten Waters of the United States (WOTUS) and oversees CERCLA emergency response and time-critical removals (TCR) of hazardous substance releases (e.g., from junkyards and mines). Given the nature of this work, the location and scope of the work is not known in advance, and decisions need to be made on a timeline that is more immediate than for long-term remediation and site closure work. Oil spills are not confined to production and storage facilities and could occur anywhere. While the focus of EPA’s emergency response efforts is on oil, incidents may involve a variety of materials, such as response to a spill of brine containing sodium chromate, which is used to prevent permafrost thaw around a buried section of the TAPS. To effectively manage emergency response and TCRs, it is important to understand where continuous and discontinuous permafrost exists, how oil and other contaminants impact and migrate through permafrost, and how thawing permafrost might impact WOTUS through changes in local hydrology.

On-scene coordinators (OSCs) are also involved in oil spill prevention through oversight of oil facilities under the Oil Pollution Act. All oil storage facilities that have >42,000 gallons (>150,000 liters) and conduct over-the-water transfers are required to prepare Facility Response Plans (FRP), and Alaska OSCs oversee over 400 FRP facilities. Oil storage facilities with capacities of 1320 gallons (≥5000 liters) and with a risk to WOTUS are required to prepare Spill Prevention and Countermeasures Plans. These plans are not required to be reviewed and approved by EPA, so the number of such facilities is unknown. EPA estimates that there are hundreds of these facilities throughout Alaska in Alaska Native villages and remote rural communities.

Permafrost thaw can cause ground settlement (subsidence) and frost jacking, which can create discharges from oil wells on the North Slope. Consequently, >160 kilometers of TAPS vertical support members in the active layer and taliks were recently replaced due to changes in underlying permafrost. In addition, permafrost thaw can alter local hydrology, which can impact migration of contaminants in the active layer. Furthermore, the secondary containment systems at some existing sites rely on permafrost (e.g., vertical sheets of metal were buried in the permafrost with the assumption that the permafrost will prevent migration of the contaminants).

EPA, in coordination with the U.S. Coast Guard, has been conducting inspections of Alaskan facilities with FRPs. Inspections in 2022 in communities outside of Kotzebue (along the northwest Alaska coast) and around Bethel (in western Alaska) revealed that thawing permafrost and coastal erosion are causing the land around infrastructure to settle, which displaced and bent that infrastructure. Permafrost thaw is disrupting oil storage facilities in Alaska Native villages, elevating risks of discharge, as well as loss of a critical resource for home heating, transportation, subsistence, and other community uses.

EPA has also been involved in some assessment and cleanup at sites⁸ that are part of the Alaska Native Claims Settlement Act (ANCSA), which are lands conveyed by the U.S. Department of Interior to Alaska Native corporations. While there are not emergency response needs on all ANCSA lands, the migration of existing contamination on the ANCSA lands could impact the permafrost or could be significantly altered by permafrost thaw. In all responses, cleanups, and removals in areas of permafrost, there is a delicate balance between cleaning up the contaminants and not impacting the permafrost.

EPA has conducted emergency response and spill prevention at oil storage facilities that are already impacted by permafrost thaw. EPA can use data that can immediately support cleanup and prevention measures. Ideally, EPA staff could access a compilation of existing and ongoing research on:

• Recommended mitigation measures for oil storage and other infrastructure in Alaska Native villages and other rural communities in areas with subsiding permafrost and coastal erosion.

• Impacts of oil facility contaminants on the active layer (e.g., describing the impact of existing ground contamination on seasonal cycles).

• Determining endpoints when working with permafrost.

• Interactions of hydrocarbons and other contaminants to permeate permafrost in both the lateral and vertical directions.

• Potential impacts of thawing permafrost on the existence of WOTUS.

Secondarily, EPA staff desire comprehensive data to geolocate permafrost throughout Alaska, including in areas of discontinuous permafrost. EPA manages interests along the TAPS, rail corridors, North Slope oil and gas production sites, and remote communities where oil is stored (e.g., in western Alaska, the Northwest Arctic, and the Interior). EPA staff noted that developing such a dataset is likely a long-term effort that may lag emergency response actions and ongoing preventative measures.

e. Harmful Algal Blooms

With warming temperatures, cyanobacterial harmful algal blooms (cyanoHABs) could increase throughout Alaska’s abundant freshwater and estuarine systems from longer ice-free periods, warmer water temperatures, increased nutrient mobilization and availability, and more suitable growth conditions for cyanobacteria. EPA and its counterparts in Alaska have determined that there are insufficient data to identify vulnerable Alaskan surface water bodies or potential cyanoHAB impacts to public water systems in Alaska. Not all public water systems are currently equipped to treat drinking water where cyanoHABs occur. To address this data gap, EPA began to identify Alaska public water systems that are at risk of experiencing cyanoHABs by compiling and evaluating existing data sources, including projection data that enable forecasting of future cyanoHAB occurrences. Permafrost thaw is anticipated to impact the location, extent, and flow characteristics of surface waters, which, in turn, may impact surface water quantity and quality (e.g., temperature, turbidity, and nutrient and carbon concentrations and loading). Therefore, understanding how changes to permafrost conditions will impact surface waters is critical to understanding how the potential increase in cyanoHABs throughout Alaska’s freshwater and estuarine systems will affect public and ecological health.

EPA can use high-resolution geospatial data that show the current and projected future extent of permafrost at a sufficient resolution to evaluate impacts to surface water bodies and water quality. Preferably, the projections would also span a range of future time periods and include likely and worst-case scenarios. The permafrost data/projections could be combined with satellite data and other existing geospatial data, so data layers should be easy to add to other GIS tools.

In addition, EPA can use a geospatial dataset of permafrost and surface water showing background conditions that can be used to compare current/future conditions with “natural background”. EPA’s partners in Alaska often use current conditions to represent background, but it would be preferable to instead use historical data to represent the changes to that background.

f. National Environmental Policy Act

Under the National Environmental Policy Act (NEPA) and Section 309 of the Clean Air Act, EPA reviews Environmental Impact Statements (EISs), such as for oil and gas development in Alaska, including several proposals on the North Slope. For these EIS reviews, EPA considers whether the proposed development will disrupt permafrost and if mitigation can be recommended to reduce those impacts. For example, well bores or other new infrastructure could weaken existing permafrost. Some EISs include thaw bulb analyses that provide data on how infrastructure might impact active layer and deep permafrost, but other EISs provide little information on existing permafrost extent, depth, and ice content and how the permafrost might be impacted by the oil and gas development.

To support evaluation of Alaska oil and gas development EISs, EPA can use geospatial data showing permafrost extent (surface area), delineations of continuous and discontinuous permafrost, and permafrost depth/volume. In addition, information on how these permafrost features could change in the future could inform the potential impacts of development and the most appropriate mitigation measures. For most EISs, permafrost projections apply to the timeline of the projected development and operations, which is often in the range of 30–50 years. For some EISs, longer-term impacts (e.g., up to 100 years in the future) would be considered.

EPA staff expressed the following additional needs for information that could be leveraged when evaluating Alaskan oil and gas development EISs:

• Feasible and recommended options to mitigate permafrost impacts when constructing infrastructure in the Arctic.

• Methods to restore permafrost that is damaged during oil and gas development (e.g., revegetation best practices).

• Information on differential impacts from infrastructure placed on permafrost of varying depth, temperature, and continuity.

• Case studies with risk assessments and suggested mitigation measures of impacts to permafrost from development.

• A thaw bulb analysis for a well bore at a typical site on the North Slope extending to a normal depth of permafrost. Industry does not provide thaw bulb analyses or data on permafrost extent/depth at development sites when the data are proprietary. This analysis could inform potential hazards mitigation and potential pathways to sources of drinking water, as related to underground injection control (see section 3i).

g. Radon and Indoor Air Quality

Radon-222 is an inert gas that is part of the decay chain for uranium-238, and it is formed in natural environments during the radioactive decay of its parent isotope, radium-226. Uranium is ubiquitous in the Earth’s crust, and the amount of radon released from soils into the air depends on the concentration of radium-226, soil porosity, soil temperature, and soil moisture. EPA (2018) shows most of Alaska with indoor radon <2 picocuries per liter (pCi L⁻¹), with some portions of southeastern Alaska with moderate indoor radon levels of 2–4 pCi L⁻¹. That map was developed using factors including geology, soil and air measurements, and information on building foundations. It was intended to help governments target risk reduction measures.

EPA uses State Indoor Radon Grants to fund ADEC for indoor radon testing, recently focused on low-income communities. Data collected by ADEC (Alaska DGGS 2023a) show widespread harmful indoor radon measurements (>4 pCi L⁻¹). Further collection of indoor radon measurements is ongoing, but it is hindered by limited funding and challenges in collecting measurements in remote areas. Thawing permafrost may release radon that naturally occurs in Arctic soils (e.g., Puchkov et al. 2021) and might cause or contribute to the radon concentrations recently measured in Alaskan homes.

To address the elevated radon that is observed in Alaska, EPA would need to evaluate whether higher-than-expected radon concentrations in Alaskan homes are impacted by thawing permafrost. This type of analysis would optimally include further collection of indoor radon measurements to provide a robust dataset for evaluation. Radon measurements should be collected continuously for 1–2 months to represent radon concentrations within a home in that season. In addition, this evaluation would require identifying or creating geospatial datasets of current permafrost conditions. EPA analysis could draw from datasets with high enough resolution to identify whether individual Alaskan communities are proximate to thawing permafrost. Optimally, the temporal resolution of the dataset would include an estimate of changes to the months when the surface-layer permafrost is seasonally active to aid in comparison to the radon measurements.

If this analysis demonstrated that thawing permafrost impacts radon concentrations in Alaskan homes, then EPA could use future projections of permafrost conditions across the inhabited areas of Alaska at a high enough spatial resolution to resolve permafrost conditions in individual communities. Optimally, these projections would represent a variety of timeframes (e.g., every 10–20 years during the 21^st century).

h. Smoke

EPA collaborates with other federal, state, local, and Tribal agencies on wildfire and prescribed fire impacts, and how to manage them. Currently, EPA develops air quality tools, such as the Fire and Smoke Map (https://fire.airnow.gov) to support regional partners in evaluating smoke impacts. EPA contributes messaging on smoke and public health that complements the localized information from other agencies. Additionally, EPA manages State Implementation Plans (SIPs) under the Clean Air Act to manage degraded air quality from particulates that could adversely affect human health. Alaska has a smoke management plan as a part of its SIP (ADEC 2021), which necessarily involves EPA. Permafrost thaw and other climatic impacts in Alaska (e.g., the lengthening of the summer season) are expected to increase wildfire prevalence and severity, which consequently could impact permafrost thaw (Teufel and Sushama 2019; Kim et al. 2024). Understanding the relationship between wildland fires (both wildfires and prescribed fires) and permafrost thaw remain important for smoke management.

i. Underground Injection Control

EPA oversees underground injection control (UIC) permits in NSB. These permits relate to deep wells (~1500–3000 meters deep) that are used for waste disposal (e.g., oil/gas drilling and production waste, slurried solid waste, and greywater), as well as other purposes, such as reverse osmosis water treatment. One historic site on Prudhoe Bay injected waste directly below permafrost, causing an environmental catastrophe. Now wells are designed for injections ~1200–1500 meters deep, but that exceeds the typical depth of permafrost in NSB (~300–600 meters).

Management of UIC permits could change if the depth of the seasonally active “permafrost table” increases in summer, e.g., 3 meters instead of 1.5 meters of thaw in an average year. Wellhead integrity and other site infrastructure could be damaged, increasing the risk of a waste spill. In addition, irreversible thaw of permafrost at a given site could impact management of UIC permits. Permanent permafrost thaw would require considering the movement of injected waste. Permafrost does not “confine” waste for UIC permits, but it restricts vertical waste movement. Irreversible permafrost thaw could increase the likelihood of waste rising above the injection level. Additionally, long-term permafrost thaw would create newly melted underground sources of drinking water (USDW) in NSB. All of EPA’s current UIC permits assume that there are no USDW in the jurisdictions, so waste can be injected above the fracture gradient within injection zones. If thawing permafrost were to create USDW, then EPA would need to determine whether these aquifers merit protection and whether there should be changes to existing or new UIC permit conditions.

To support this work, EPA staff requested:

• Current extent and depth of permafrost at UIC permit sites in NSB at a resolution to determine impacts to wellheads and other infrastructure (i.e., ~3–6 meters, if feasible). Coarser spatial resolution could be considered with continuous permafrost.

• Predictions of active layer depth at the UIC permit sites in NSB at mid-century.

• Projections of if/when permafrost will permanently thaw at the UIC permit sites and surrounding areas. If hazardous waste injections are authorized in the future, EPA would need to plan for impacts on a geologic time scale (e.g., ~10,000 years). Therefore, projections of complete permafrost thaw are relevant, even if thaw occurs beyond this century.

• Predictions on how anticipated permafrost thaw will affect soil permeability, groundwater flow, and the development of underground aquifers, thaw bulbs, and taliks in NSB. This need is also related to thaw bulbs under NEPA, and there could additional implications for methane emitted from thawed permafrost (see section 3k).

j. Wastewater and Water Infrastructure Engineering

EPA works with the State of Alaska and the Alaska Native Tribal Health Consortium to ensure that wastewater and water infrastructure remain operational in Alaska communities, including those in areas of discontinuous and continuous permafrost. Permafrost thaw can cause infrastructure failure, although the rate of permafrost change facilitates developing engineering solutions to mitigate thaw impacts. Thawing permafrost is identified using ground temperature measurements or by association with damaged infrastructure (e.g., underground pipe failure). Infrastructure is sited to minimize risk by avoiding areas prone to thaw or by incorporating design solutions to prevent infrastructure failure when thaw occurs. In addition, design solutions, such as thermosiphons, can mitigate warming of permafrost by the infrastructure itself. Interviewees did not identify new permafrost data needs for engineering wastewater and drinking water infrastructure, but their activities likely would benefit from additional data and tools suggested elsewhere.

k. Other Permafrost Concerns

In addition to the permafrost concerns that were hypothesized prior to conducting the interviews, regional staff raised four additional environmental concerns related to permafrost thaw. Regional staff expressed an interest in keeping these topics at the forefront as data and tools are developed, as these major topics relate to the EPA’s mission to protect human health and the environment.

1. Methane emissions from permafrost and their contributions to atmospheric warming.

2. The potential for permafrost thaw to release nascent infectious diseases.

3. Increasing carbon emissions from Arctic wildfires due to warming.

4. Production of natural gas from hydrate deposits that are located within and below permafrost and below the seafloor.

4. Available Tools and Data Resources

The 2022 survey of the EPA regional staff revealed that no tools and resources comprehensively met the needs for assessing and quantifying the risks of permafrost thaw in Alaska on the people and environment (described in section 3). However, several resources contain useful information that can support projects in areas that currently have permafrost. The resources (Table 1), identified through the interviews and through internal research projects, can be used to partially address environmental concerns in areas impacted by permafrost thaw.

5. Summary

Permafrost thaw is occurring throughout Alaska, particularly in the NSB which borders the Arctic Ocean. Continued warming temperatures in Alaska could exceed a tipping point where the areal extent and depth of permafrost will be significantly reduced in the near-surface layers (e.g., Peng et al. 2023; Guo et al. 2023), with potentially dire environmental consequences for many communities in northern Alaska. Understanding these consequences and providing potential timelines are critical to mitigating environmental and human impacts in these communities. The interviews in this study articulated a broad overview of knowledge and data gaps related to permafrost in Alaska, providing impetus to explore options to address these needs. These interviews revealed science and research needs that span technical and policy expertise.

Characterizing permafrost conditions is a multifaceted challenge. Mapping the locations, areal extent, and depth of permafrost is important. Additionally, data are needed on the evolution of characteristics (including continuous vs. discontinuous), physical stability, hydrology, and biogeochemistry associated with permafrost. However, none of the existing tools (Table 1) holistically meet these needs. EPA staff desired a user-friendly geospatial tool that includes measured and modeled data on current permafrost conditions and modeled future permafrost conditions that could meet numerous Agency needs. Specific features for the tool include:

• Permafrost data throughout Alaska at a sufficient spatial resolution to support decision making.

• Permafrost projection data at mid-century and end-of-century.

• Permafrost projections representing “likely” and “worst-case” scenarios.

• The areal extents of continuous and discontinuous permafrost, permafrost/ground temperature, permafrost depth, depth of seasonally active layer, and areas susceptible to permafrost thaw.

• Soil, water, and geochemical conditions associated with present and future permafrost conditions.

• Sufficient information to track contaminated groundwater flows through continuous, discontinuous, and thawing permafrost.

Interviewees highlighted the need for permafrost-related data with sufficient resolution to assess impacts to infrastructure, downstream water quality, and hydrogeochemical and physical interactions that may have impacts at regional to household scales. Affected infrastructure can be quite small (e.g., a well head might be 3–6 meters in diameter, a home might be 50–100 m², and an average RCRA site is approximately 1000–2000 m²). However, continuous permafrost across a region justifies lower-resolution data if surface and subsurface conditions are comparable across that area. The trade-offs between resolution, accuracy, and resources to develop data layers require consideration.

Interviewees stressed that permafrost thaw is already significantly impacting Alaska Native villages. Assistance is needed to develop and compile resources that can immediately help those villages, including available technologies to preserve permafrost and counteract thaw surrounding critical infrastructure, mitigation measures for preserving infrastructure in areas with permafrost thaw and coastal erosion, information on contaminant spread through permafrost and the active layer, and best practices for building and relocating community resources and infrastructure in areas experiencing permafrost thaw. Multiple interviewees clamored for advice from expert scientists to interpret the projections and information provided in any new tool or resource. Mitigation measures for thaw can be expensive and time-consuming to implement, so accurate interpretation of the projections is foundational for conversations with communities and facilities impacted by permafrost thaw.

Interviewees also emphasized collaboration with the multitude of stakeholders already working on permafrost topics in Alaska (i.e., federal and state agencies, consortia, international committees, and universities) so that EPA can supplement and complement ongoing efforts. EPA is active in the Interagency Arctic Research Policy Committee, Northern Bering Sea Climate Resilience Area Task Force, Arctic Executive Steering Committee, NOAA Alaska Regional Collaboration Network, Navigating the New Arctic working group, and Alaska Native Tribal Health Consortium. EPA may bolster its collaborative activities to amplify the need to acquire data and knowledge related to permafrost characteristics in Alaska.

This study tabulated environmental issues across Alaska that could be impacted by permafrost thaw and are under the purview of the EPA. The interviewees revealed sources of data that are considered in decision making, and they identified gaps in data that would be useful to holistically consider impacts of permafrost thaw on a plethora of concerns. The study was comprehensive, but it does not reflect nascent issues related to permafrost thaw that have arisen (e.g., movement of metals) or tools that have been developed, (e.g., https://arcticeds.org and https://permamap.gi.alaska.edu) since the interviews were conducted. In addition, interviewees emphasized their desire for an interactive geospatial tool, which underscores the importance of increased field-collected measurements and long-term monitoring data to populate the tool and validate numerical models. The absence of these measurements—and research to exploit them—would necessarily limit the utility of tools, models, and maps to mitigate the localized environmental impacts of permafrost thaw in Alaska. This study motivates strategic research to quantify impacts of increasing temperatures on permafrost in Alaska. Specifically, this study provides impetus to formalize internal and external collaborations to further the understanding and quantification of the potential impacts of thawing permafrost on Alaskan communities, infrastructure, and environmental interests.

SIGNIFICANCE STATEMENT.

Permafrost (or perennially frozen ground) is widespread in Alaska. It serves vital roles for communities and ecosystems, including infrastructure support, natural refrigeration, and insulation from contaminant seepage from waste disposal and other sources. Rapid warming in Alaska is compromising permafrost, which can create adverse environmental and health risks. Internal interviews at the U.S. Environmental Protection Agency revealed knowledge and data gaps to improve understanding of the current state and future characteristics of permafrost. Regulators need to understand the extent and depth of permafrost—and the timing and changes to that permafrost—at a fine spatial resolution to inform adaptation activities in partnership with state, local, and Tribal leaders. Filling those gaps facilitates protecting the people, resources, and ecosystems in Alaska.

Data Availability Statement.

No datasets were generated or analyzed during the current study.