B
Permafrost Working Group
Permafrost core retrieved near the Tanana River. Photo: UAF - T. Paris
Two researchers measure depth to permafrost in a recently burned area. Photo: C. Truettner
Examining a thermokarst feature in Denali National Park and Preserve. Photo: E. Lathrop
Research at the Alaska Peatland Experiment (APEX).
Students record soil and vegetation data along a tape transect. Photo: UAF - K. Huo
Collecting greenhouse gas samples in a permafrost-affected fen ecosystem. Photo: C. Dieleman
Co-Leads
Jeremy Jones
Professor of Biology
University of Alaska Fairbanks
Catherine Dieleman
Assistant Professor of Boreal Forest Ecology
University of Guelph
Ted Schuur
Regents’ Professor
Northern Arizona University
Collaborators
Merritt Turetsky
Professor of Ecology and Director of Arctic Security
University of Colorado Boulder
Evan Kane
Professor, College of Forest Resources and Environmental Science
Michigan Technological University
Tamara Harms
Associate Professor, Environmental Science Department
University of California, Riverside
Eugenie Euskirchen
Professor
University of Alaska Fairbanks
Michelle Mack
Regents’ Professor
Northern Arizona University
Xanthe Walker
Assistant Professor
Northern Arizona University
Soils that remain frozen for two or more consecutive years are considered ‘permafrost’ soils. These soils contain large amounts of organic material that has built-up from plant, microbe and animal inputs, often over centuries to millennia. Widespread warming across boreal Alaska is currently destabilizing permafrost, exposing its organic material to microbial decomposition and loss via leaching to aquatic ecosystems. Permafrost thaw processes can unfold either abruptly or gradually. Gradual thaw influences surficial permafrost over decades to centuries, while abrupt thaw unfolds over years to decades and creates fundamental shifts in local hydrology, geomorphology, and vegetation. These thaw processes are leading to the expansion of perennial thaw zones above the permafrost table (taliks) that remain unfrozen during the winter, even with permafrost below and frozen soil above. Talik formation represents a unique subsurface ecosystem that can further alter carbon and nutrient transfer into aquatic ecosystems at new times of the year. Combined, these permafrost thaw processes are fundamentally altering both gaseous and aquatic-phase carbon and nutrient transport across Alaska, potentially destabilizing old legacy C stores that have been held on the landscape for thousands of years. By returning these stores to the atmosphere as CO2 and CH4, permafrost thaw processes form one of the most important identified feedbacks to climate change.
Our working group is working on delineating this feedback by assessing the effects of thawing permafrost on hydrologic processes, the loss of carbon to the atmosphere, and export of both carbon and nutrients into aquatic ecosystems across a range of permafrost ecosystems in interior Alaska. We are considering four foci questions (see below) that allow us to work across upland boreal, wetland, and alpine tundra ecosystems ( (CPCRW, EML, APEX, and RSN study sites). Most of our research sites have a history of ongoing research, and we are working to understand the longer-term trends and patterns over the past 20+ years. Our work is led by Jones, Dieleman, and Schuur with membership that includes Euskirchen, Harms, Kane, Mack, Turetsky, Waldrop, and Walker.
How will increased evapotranspiration and changing precipitation interact with thawing permafrost to affect soil moisture within terrestrial ecosystems and runoff into aquatic ecosystems?
Alaska’s boreal forest is experiencing broadscale hydrologic change in the timing and form of precipitation, frequency of drought, and river discharge. Over the past century, summer drought conditions have become more frequent due to increased evapotranspiration. The effect of changes in the timing and amount of precipitation on ecosystem functioning are modulated by the distribution of permafrost, which forms a barrier restricting infiltration of surface water. In upland catchments, permafrost degradation may lead to drying of surface soil and reduced streamflow as the barrier recedes deeper in the soil profile. In lowland ecosystems, low gradient combined with subsidence caused by local permafrost degradation maintains saturated soils and ponding of surface waters.
How will the degradation of permafrost and the development of taliks in three long-term upland and lowland study sites alter the release of permafrost C to the atmosphere, and C and nutrients to aquatic ecosystems?
In upland landscapes, loss of permafrost will likely lead to deepening flowpaths through catchments, surface soil drying, and increased soil aeration. This will accelerate loss of soil organic matter via microbial decomposition as CO2 but also as lateral transport of C in water. In contrast, thawing of lowland permafrost landscapes and impounding of water may reduce microbial decomposition rates and stimulate the production of CH4. As active layer thickness increases and winter soil temperatures warm, perennial thaw zones can transport water and solutes throughout winter. Microbial activity can persist year-round, resulting in the production of trace gases and mobilization of DOC and other solutes that can be transported into aquatic ecosystems.
How will abrupt thaw with thermal erosion affect the mobilization of permafrost C, nutrients, and trace gases in contrast to permafrost degradation without thermal erosion?
The fate of permafrost C and nutrients depends on the rate of thaw and the mode of permafrost loss (e.g., active layer thickening and subsidence vs. thermal erosion). Large-scale climate models that include permafrost thaw only simulate gradual vertical thickening of the active layer. However, in soil where ice volume exceeds pore space, thaw results in ground subsidence. In some upland landscapes, abrupt thaw and thermal erosion can rapidly mobilize sediment, nutrients, and C, whereas in lowlands, thaw can lead to ponding of surface water and lateral expansion of thaw. If abrupt thaw leads to saturated soils, C mineralization can be limited by oxygen availability and increased CO2 production.
How does fire severity interact with ground ice to determine rates of thaw and loss of permafrost C?
Climate warming and wildfire interact to increase rates of permafrost thaw because of combustion of the insulating SOL. Recovery to the pre-fire state is less likely now than in the past due to continued changes in climate and fire regimes, combustion of legacy C, post-fire changes in successional trajectories, and widespread abrupt thaw and ground collapse that exposes deep old permafrost C to decomposition. Site characteristics such as the amount of ground ice or degree of abrupt thaw and ground subsidence may predict state change and the mobilization of legacy C, which could influence global climate due to large stores of permafrost soil C.
The permafrost working group collaborates across research sectors, working particularly closely with government organizations to anticipate the cascading impacts of permafrost decay across Alaskan and polar north landscapes. Our collaborative work demonstrates that northern permafrost thaw is unfolding rapidly, resulting in a restructuring of both local and downstream aquatic ecosystems. However these impacts are mediated by thermal erosional processes. Combined, our program provides the scientific community with the tools and knowledge base needed to foresee the potential deleterious effects of permafrost thaw as well as ecological strategies to mitigate and minimize these impacts where possible.
- Synoptic measurement of stream and atmospheric indicators to improve the monitoring and prediction of climate-induced permafrost degradation across Alaska: Merritt Turetsky, Tamara Harms, Department of Defense (USA)
- Victoria Robertson: Masters of Environmental Science (MES) Student, University of Guelph - 2023
- Will Cox : PhD Student, University of Colorado Boulder - 2025
- Alyssa Tinella: B.Sc Honours Thesis student, University of Guelph - 2025
- Campbell Lewis: B.Sc. Student, University of Guelph - 2025
- Maddie Pitzer: B.Sc Student, Michigan Tech University - 2025
- Frances Iannucci: M.S. University of Alaska Fairbanks - 2023
