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TABLE OF CONTENTS Acknowledgements ..................................................................................4 Executive Summary with Key Findings and Recommendations ............5 Current State of the Art .............................................................................5 Key Scientific Challenges and Recommendations ..................................5 Major New Synthesis Initiative Required ...................................................6 Implementation of Arctic-CHAMP .............................................................6 Policy Implications ....................................................................................7 Summary ..................................................................................................8...
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The impact of recent climate change on permafrost distribution was evaluated by repeating the 1964 survey of Roger Brown along the Alaska Highway from Whitehorse, YT to Fort St. John, BC in August 2007 and 2008. Results demonstrate that: (1) significant degradation of permafrost has occurred over the past four decades, especially in the southernmost part of the route where 67% of the permafrost sites in 1964 no longer exhibit perennially frozen conditions; (2) the mapped southern limit of discontinuous permafrost appears to have shifted roughly 75 km northward; (3) most of the permafrost still present in the study area is in peat or under thick organic mats, which probably relates to a large thermal offset or to...
Abstract. To determine the influence of fire and thermokarst in a boreal landscape, we investigated peat cores within and adjacent to a permafrost collapse feature on the Tanana River Floodplain of Interior Alaska. Radioisotope dating, diatom assemblages, plant macrofossils, charcoal fragments, and carbon and nitrogen content of the peat profile indicate ~600 years of vegetation succession with a transition from a terrestrial forest to a sedge-dominated wetland over 100 years ago, and to a Sphagnum-dominated peatland in approximately 1970. The shift from sedge to Sphagnum, and a decrease in the detrended tree-ring width index of black spruce trees adjacent to the collapse coincided with an increase in the growing...
Fire has a major impact on many of the world's ecosystems. In addition to being an important part of many landscapes, fire has had a long presence in natural systems. In order to persist amid fire, many plant species have evolved various strategies to deal with fire. Many members of the genus Pinus are associated with fire-prone systems and exhibit a wide range of fire strategies. In Chapter 1, we explored the parallel (or repeated) evolution of fire strategies within the genus Pinus and reconstructed the geographic center of origin within the genus. We congruently examined the reconstruction of the origin of fire strategies and geographic center of origin to discuss potential relationships between evolution of...
Long-term lake area change has previously been measured to detect the temporal rate and spatial extent of permafrost degradation. However, the natural intra- and interannual variability of lake areas has not been considered explicitly and quantitatively, which can substantially interfere with the detection of long-term lake area change associated with permafrost degradation. In order to better understand the natural background variability of lake areas, we used Landsat 7 images obtained on 11 dates from 1999 to 2002 to quantify the intra- and interannual lake area variability for a 4224 km2 study area within the Yukon Flats, Alaska. Total lake areas ranged from 179 km2 (22 August 1999) to 326 km2 (6 June 2000)....
Spatial patterns in carbon (C) and nitrogen (N) cycles of high-latitude catchments have been linked to climate and permafrost, and used to infer potential changes in biogeochemical cycles under climate warming. However, inconsistent spatial patterns across regions indicate that factors in addition to permafrost and regional climate may shape responses of C and N cycles to climate change. We hypothesized that physical attributes of catchments modify responses of C and N cycles to climate and permafrost. We measured dissolved organic C (DOC) and nitrate (NO3–) concentrations, and composition of dissolved organic matter (DOM) in 21 streams spanning boreal to arctic Alaska, and assessed permafrost, topography, and attributes...
Arctic and subarctic watersheds are undergoing climate warming, permafrost thawing, and thermokarst formation resulting in quantitative shifts in surface water –groundwater interaction at the basin scale. Groundwater currently comprises almost one fourth of Yukon River water discharged to the Bering Sea and contributes 5–10% of the dissolved organic carbon (DOC) and nitrogen (DON) and 35–45% of the dissolved inorganic carbon (DIC) and nitrogen (DIN) loads. Long-term streamflow records (>30 yrs) of the Yukon River basin indicate a general upward trend in groundwater contribution to streamflow of 0.7–0.9%/yr and no pervasive change in annual flow. We propose that the increases in groundwater contributions were caused...
Discontinuous permafrost in the North American boreal forest is strongly influenced by the effects of ecological succession on the accumulation of surface organic matter, making permafrost vulnerable to degradation resulting from fire disturbance. To assess factors affecting permafrost degradation after wildfire, we compared vegetation composition and soil properties between recently burned and unburned sites across three soil landscapes (rocky uplands, silty uplands, and sandy lowlands) situated within the Yukon Flats and Yukon-Tanana Uplands in interior Alaska. Mean annual air temperatures at our study sites from 2011 to 2012 were relatively cold (-5.5 degrees C) and favorable to permafrost formation. Burning...
This study is the first known attempt in North America to use the basal temperature of snow (BTS) method to predict the distribution of mountain permafrost. The study site, Wolf Creek Research Basin, Yukon Territory (60°30'N, 135°13'W), is a 195 km 2 basin ranging in elevation from 650-2100 m with a mean annual air temperature of about -4°C at 1235 m a.s.l. A modeled BTS surface, based on 394 measured BTS values and with elevation and potential incoming solar radiation as independent variables, was created within a GIS environment with an r2 value similar to European results. The distribution of permafrost within the basin was identified from pits and boreholes. A subsequent logistic regression was used to compare...
Permafrost thaw in peat plateaus leads to the flooding of surface soils and the formation of collapse scar bogs, which have the potential to be large emitters of methane (CH4) from surface peat as well as deeper, previously frozen, permafrost carbon (C). We used a network of bubble traps, permanently installed 20?cm and 60?cm beneath the moss surface, to examine controls on ebullition from three collapse bogs in interior Alaska. Overall, ebullition was dominated by episodic events that were associated with changes in atmospheric pressure and ebullition was mainly a surface process regulated by both seasonal ice dynamics and plant phenology. The majority (>90%) of ebullition occurred in surface peat layers, with...
Only a small boby of research addresses the impacts of timber harvesting in the boreal forest of Alaska. The two projects described here began in 1970 and 1980 to develop more reliable methods of regenerating white spruce—the main commercial species in interior Alaska—from seed, and quantifying vegetation and soil responses. A "by-product" of timber harvest is increased moose browse and cover provided by deciduous saplings (birch, popular, and aspen) and brush species such as willow. The importance of moose in the economy of interior Alaska guarantees a major role in the values behind forest management decisions. Recent reevaluations of both projects has significant implications for the management of white spruce...
This study is the second attempt to use the Basal Temperature of Snow (BTS) method to map permafrost in mountainous regions of northwestern Canada. It differs from the first study which took place in Wolf Creek in terms of (1) the methodology used to evaluate BTS, (2) the strategy used to avoid spatial autocorrelation in residuals, and (3) the climatic regions investigated. Two study areas, part of the Ruby Range (61° 12' N, 138° 19' W) and Haines Summit (59° 37' N, 136° 27' W) were selected for BTS sampling based on differing climatic conditions and previous knowledge of permafrost elevations from active rock glaciers. A total of 30 BTS measurements were made in the Ruby Range in the winter of 2006 and a total...
This research presents a method for permafrost mapping in discontinuous permafrost regions based on equivalent latitude/elevation concept in interior Alaska. In winter months, study site has a strong temperature inversion in air up to 700 m elevation. Air temperature data and the effects of slope, aspect and elevation were used to create an equivalent latitude/elevation model. This model was well correlated with mean annual surface temperature (0.79). In this watershed, the thawing index (I sub(t) approximately 1 400 degree C times days) at the ground surface and snow depth do not vary greatly from south facing to north facing slopes. The primary controlled factor that determines the mean annual surface temperature...
Positive and negative species interactions are important factors in structuring vegetation communities. Studies in many ecosystems have focussed on competition; however, facilitation has often been found to outweigh competition under harsh environmental conditions. The balance between positive and negative species interactions is known to shift along spatial, temporal and environmental gradients and thus is likely to be affected by climate change. Winter temperature and precipitation patterns in Interior Alaska are rapidly changing and could lead to warmer winters with a shallow, early melting snow cover in the near future. We conducted snow manipulation and neighbour removal experiments to test whether the relative...
map background search result map search result map Temperature and peat type control CO2 and CH4 production in Alaskan permafrost peats Thermal Performance of the Permafrost Protection Techniques at Beaver Creek Experimental Road Site, Yukon, Canada Climate Change in Central Yukon Historic Change in Permafrost Distribution in Northern British Columbia and Southern Yukon Territory, Canada Thermal Performance of the Permafrost Protection Techniques at Beaver Creek Experimental Road Site, Yukon, Canada Historic Change in Permafrost Distribution in Northern British Columbia and Southern Yukon Territory, Canada Temperature and peat type control CO2 and CH4 production in Alaskan permafrost peats Climate Change in Central Yukon