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Air and ground temperature at eleven sites within various biogeoclimatic zones along a N-S cross-section of Lightning Creek valley, near Keno, demonstrate the significance of atmospheric inversions on mean annual temperature. The mean annual air temperature increases with elevation by 2.2°C over the lower 160 m of Keno Hill, but declines above this level. Permafrost is present on the N-facing slope of Sourdough Hill but is absent on part of the S-facing aspect of Keno Hill, due to winter inversions and high summer solar radiation. The association of biogeoclimatic zones with permafrost was defined with thermal and physical data from the sites. With vegetation interpreted from aerial photographs and topographic information...
In the northern high latitudes, vegetation distribution and carbon cycling have been continuously changed in the past and could change more rapidly as the climate warming. The purpose of my PhD dissertation is to quantify the uncertainty in modeling vegetatidynamics and to assess the effect of permafrost on vegetation dynamics and carbon cycling in the northern high latitudes under different levels of warming conditions. The uncertainty in current modeling of vegetation dynamics is considerably large. The first part of this study is to assess how high-latitude vegetation may respond under various climate scenarios during the 21st Century with a focus on analyzing model parameters induced uncertainty and how this...
Fire is an important factor controlling the composition and thickness of the organic layer in the black spruce forest ecosystems of interior Alaska. Fire that burns the organic layer can trigger dramatic changes in the underlying permafrost, leading to accelerated ground thawing within a relatively short time. In this study, we addressed the following questions. (1) Which factors determine post-fire ground temperature dynamics in lowland and upland black spruce forests? (2) What levels of burn severity will cause irreversible permafrost degradation in these ecosystems? We evaluated these questions in a transient modeling-sensitivity analysis framework to assess the sensitivity of permafrost to climate, burn severity,...
Old Crow Flats is a 5600 km2 glaciolacustrine plain that straddles the forest-tundra ecotone in northern Yukon. Continuous taiga corridors occur in the entrenched river valleys, where annual mean ground temperatures (Tg) at the depth of zero annual amplitude at two locations were ?3.1 and ?4.0ºC in 2013. On the Flats, the vegetation cover is patchy, and Tg varied between ?5.1 and ?2.6ºC. Annual mean near-surface permafrost temperatures (Tps) measured on the Flats between 2008 and 2011 in patches of taiga, tall shrubs and low shrubs were correlated with local snow depth. Snow depth was controlled by vegetation height if the snow supply was not limited, for example, where low shrubs and large lakes dominate the landscape....
We used the CRU (1950-1959 and 2000-2009) and projected 5-GCM composite (2001-2010, 2051-2060, and 2091-2100) decadal climate forcing, ecotype (Jorgenson et al. 2008), soil landscape (Jorgenson et al. 2008), and snow (unpublished) maps of WRST to model the presence or absence of near-surface permafrost, temperature at the bottom of seasonal freeze-thaw layer and thickness of seasonal freeze-thaw layer within WRST. We produced permafrost temperature and active-layer and seasonally-frozen-layer thickness distribution maps through this modeling effort at a pixel spacing of 28.5 m. This is an immense improvement over the spatial resolution of existing permafrost maps on any part of Alaska, whether produced through the...
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...
Issue Title: Hydrogeology of Cold Regions Research on large northern rivers suggests that as permafrost thaws, deeper groundwater flowpaths become active, resulting in greater baseflow, increased concentrations of weathering ions and reduced concentrations of dissolved organic carbon in the streamflow. In contrast, at the headwater-catchment scale, where understanding of groundwater/surface-water interactions is developed, inter-annual variability in climate and hydrology result in complex hydrological and chemical responses to change. This paper reports on a 4-year runoff investigation in an alpine discontinuous permafrost environment in Yukon, Canada, using stable isotopes, major dissolved ions and hydrometric...
Upland soils formed in three different parent materials in the Lewes Plateau of the Central Yukon were studied: till from the McConnell (MIS 2) and penultimate (MIS 4 or 6) glaciations, and weathered bedrock beyond the penultimate limit Soils at penultimate and McConnell sites have solum thicknesses of 50-75 cm and <50 cm respectively but other field and chemical observations did not identify differences in weathering patterns between age groups. The two groups have distinctive clay mineral assemblages, with smectite present in the youngest deposits. These results contrast with reconnaissance studies conducted in the 1970s and 1980s on low-elevation soils in the Klondike Plateau. My study shows that field criteria...
Detailed observations of stream, soil, and groundwater chemistry were used to determine the role of fire, permafrost and snowmelt processes on the fluxes of carbon, nitrogen and major solutes from interior Alaskan catchments. We examined an experimentally burned watershed and two reference watersheds that differ in permafrost coverage (high, 53%; medium-burn, 18%; and low, 4%) during the FROSTFIRE prescribed burn in July 1999. The fire elevated stream nitrate concentrations for a short period during the first post-fire storm, but nitrate declined thereafter, suggesting that less severe fires that leave an intact riparian zone may have only a short-term effect on stream chemistry. Nevertheless, we found fundamental...
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 approximately 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...