Recent summaries of international research clearly document the past and future extent of climate warming in the Arctic. These summaries suggest that in the future, rising temperatures will be accompanied by increased precipitation, mostly as rain: 20% more over the Arctic as a whole and up to 30% more in coastal areas during the winter and autumn. These climate changes will have important impacts on Arctic Systems. Of direct interest to this research is the likelihood that warming will promote permafrost degradation and thaw. Formerly frozen soils may be further destabilized by increased precipitation, leading to hillslope thermokarst failures. Recent work has documented that thermokarst failures are abundant and appear to have become more numerous around Toolik Lake on the eastern North Slope and in the western Noatak River basin in Alaska. A widespread and long-term increase in the incidence of thermokarst failures may have important impacts on the structure and function of arctic headwater landscapes. This research will use a systems approach to address hypotheses about how thermokarst failures influence the structure and function of the arctic landscape. It will focus on the composition of vegetation, the distribution and processing of soil nutrients, and exports of sediments and nutrients to stream and lake ecosystems. Results obtained at this hillslope scale will be linked to patterns observed at the landscape scale to test hypotheses about the spatial distribution of thermokarst failures in the arctic foothills. It is important to understand these interactions because perhaps the greatest potential impacts of changing land surface processes and formation of thermokarst failures are feedbacks to the climate system through energy, albedo, water, and trace gas exchange.
This research is designed to quantify linkages among climatology, hillslope hydrology, geomorphology, geocryology, community ecology of vegetation, soil nutrient dynamics, microbial ecology, trace gas dynamics, and aquatic ecology. It will employ a combination of field experimentation, remote sensing, and simulation modeling as a means to quantify these relationships.
Thermokarst failures are features of permafrost landscapes, which form due to collapse of soil structure with permafrost thaw. Our broader collaborative project addressed hypotheses about how thermokarst failures influence the structure and function of the arctic landscape. Specifically we focused on geomorphology, composition of vegetation, distribution and processing of soil nutrients and organic matter, and exports of sediments and nutrients to stream and lake ecosystems. We hypothesized that a widespread and long-term increase in the incidence of thermokarst failures will have important impacts on the structure and function of arctic headwater landscapes. At the University of Alaska Fairbanks, investigators focused on five components of the broader collaborative project: 1) the consequences of thermokarst failures for soil carbon and nutrients, 2) landscape scale characterization of modes of thermokarst failure, 3) thermokarst failure detection using remote sensing, 4) native Alaskan' perceptions of thermokarst failures in their landscape, and 5) outreach and education. Soil respiration in thermokarst features was spatially heterogeneous with CO2 flux from some areas significantly elevated above the flux from intact tundra, but depressed from exposed mineral soil. Interestingly, at the scale of whole thermokarst failures, CO2 flux to the atmosphere was not substantially different than from intact tundra. Methane and nitrous oxide (greenhouse gases) concentrations were similarly heterogeneous. Methane concentration was generally lower in thermokarst soil compared with undisturbed tundra, except in soil that had been re-vegetated. Nitrous oxide was elevated in regions of the thermokarsts where soil drying had occurred. This elevated nitrous oxide indicated that the microbial process of denitrification was occurring, which is thought to be low in tundra soil. Recently formed thermokarst failures also influence soil water chemistry with dissolved organic carbon, dissolved organic nitrogen, and inorganic nutrient concentrations elevated compared to nearby water tracks. However, the chemistry of water rapidly returned to pre-failure concentrations as thermokarst features stabilized. Biodegradability of organic carbon released from thermokarst features was also significantly elevated. At several sites, DOC biodegradability exceeded 60 % loss, making this some of the most bioavailable DOC ever reported in natural waters. Ground ice morphology and volume were found to be fundamental factors affecting the type of thermokarst features at sites near Toolik Lake and in Noatak National Preserve. The dominant types of ice were buried glacial ice associated with glacial thermokarst, and segregated ice in the intermediate layer of upper permafrost associated with active-layer detachment slides. Differences in ground ice characteristics create unique patterns of differential thaw settlement and slumping. Over 80% of active retrogressive thaw slumps examined in our study were first detected in remote sensing imagery in the summer 2004. While 2004 was record-setting warm temperature for much of the state, weather data from the Noatak Basin indicate summer temperature and precipitation were close to average. However, in summer 2004, the Noatak basin warmed rapidly in early summer and two two intense rainstorms occurred in May. Snowmelt during spring 2004 was also early. Community residents in Selawik and Anaktuvuk Pass with extensive knowledge of the local landscape guided us to sites that show evidence of thermokarst processes in and around each village. Interviewees helped us to construct local knowledge maps showing patterns of local travel, subsistence activities, and features attributed to changing permafrost conditions. Residents in both communities voiced concerns about the impacts climate and permafrost changes may have on their subsistence practices. Both communities reported increased shoreline erosion and turbidity of water bodies, with greater concern in Selawik. Most Selawik respondents believe their community will need to modify drinking water systems, change ways of local travel, and relocate buildings to adapt to thawing permafrost. Through professional development workshops for teachers in Alaska and other states, more than 4,000 students have been reached. Alaska Native students were engaged in scientific investigations and a group of Alaska rural students were introduced to life as a scientist and conducting fieldwork. More than 100 Alaskan rural communities, through their schools have been engaged in monitoring permafrost temperatures and the depth of the active layer. For education and outreach, our project resulted in the training of three Ph.D. students, and contributed to one postdoctoral scholar obtaining a tenure-track faculty position. The course "Introduction to Changing Permafrost in the Arctic Landscape" that was taught by the principal investigators, post-doctoral fellows, and graduate students, reached a diverse audience locally, statewide, nationally, and globally including students in Moscow, Australia, Korea, several National Laboratories, US and Canadian agencies, and private industries and consulting firms. Overall, our professional career development webinar reached participants in more than 20 countries.
