Warming over the past century has been greatest in high-latitudes over land and a number of environmental indicators suggest that the Arctic climate system is in the process of a major transition. Given the magnitude of observed and projected changes in the Arctic, it is essential that a better understanding of the characteristics of the Arctic climate system be achieved. In this work, I report on modifications to the UVic Earth System Climate model to allow it to represent regions of perennially-frozen ground, or permafrost. I examine the model’s representation of the Arctic climate during the 20th Century and show that it capably represents the distribution and thermal state of permafrost in the present-day climate system. I use Representative Concentration Pathways to examine a range of possible future permafrost states to the year 2500. A suite of sensitivity experiments is used to better understand controls on permafrost. I demonstrate the potential for radical environmental changes in the Arctic over the 21st Century including continued warming, enhanced precipitation and a reduction of between 29 and 54 % of the present-day permafrost area by 2100. Model projections show that widespread loss of high-latitude wetlands may accompany the loss of near surface permafrost. / Graduate

No description available.

The overall goal of this study was to examine the hydrological and geochemical linkages between the contributing landscape and small tundra lakes affected by shoreline retrogressive thaw slumping (SRTS) in the upland region north east of Inuvik, NT. In 2007, 2008, and 2009, detailed hydroclimatological and geochemical data were obtained from a pair of representative tundra lake catchments (Lake 5A: Control; Lake 5B: Affected by SRTS). This was supplemented with less detailed data obtained from 10 regional small tundra lake catchments (control and affected by SRTS). The hydrology and geochemistry of Lake 5A and Lake 5B exhibited strong seasonal variability that was characterized by spring snowmelt. For the three study years, Lake Level (LL) peaked during spring snowmelt, when the addition of melt water from the contributing landscape led to a rapid rise in LL that was enhanced by snow and ice damming the outlet channel. The addition of this relatively dilute runoff water led to a decrease in the concentration of most major ions and nutrients in the study lakes over the spring months. Notably, the concentration of nutrients increased at the beginning of spring snowmelt, due to the mobilization of surficial organic materials by runoff, before decreasing as runoff to the lake became more diluted. Recent changes in key hydroclimatic factors have likely affected the hydrology and geochemistry of the study lakes. The examination of a suite of hydroclimatic indicators, derived from historical climate data, indicated that the annual May 1st snowpack in Tuktoyaktuk has been increasing at a significant rate over the past half century. Furthermore, detailed snow survey data suggested that the capture of snow by SRTS-affected terrain increases the snowmelt contributions to small tundra lakes. An increase in the contribution of snowmelt inputs to the lake water balance could lead to a higher peak LL and more dilution of lake water. In addition to hydro-climatic drivers, the geochemistry of the study lakes was also driven by SRTS. SRTS-affected lakes had significantly higher concentrations of major ions than unaffected study lakes, due to the addition of relatively ion-rich runoff from SRTS-affected terrain during the spring and summer months. The outlet channels draining the SRTS-affected study lakes also had significantly higher concentrations of major ions than that of the unaffected study lakes, due to the addition of relatively ion-rich lake water, which suggests that SRTS-affected lakes could be a source of major ions to downstream lakes. / Graduate

No description available.

No description available.

The evolution of the landscape of Vestfirđir, made almost entirely of volcanic rocks, is traced from the lilocene, when the oldest rocks formed, through the Pliocene and Pleistocene. Volcanic activity ceased first in the north western part leaving a basalt plateau with occasional large volcanoes protruding. Fluvial erosion, guided by a westerly dip of the plateau and tectonic lineaments, left a well developed drainage pattern there by the rime volcanic activity ceased in the southeast. The snowline fluctuated widely during the Plio-Pleistocene. Cirque and valley glaciations were very effective in sculpturing the landscape where the preglacial relief was greatest, in the northwest. Ice sheet glaciations affected the whole peninsula and offshore areas with linear erosion dominant in the northwest and areal scouring elsewhere. The glacial geomorphology of Dyrafjorour and northern Arnarfjorour is mapped. The highest marine limit is in the Nupur area, about 110 m, and shorelines and marine limits higher than 70 m are at 7 other localities at least. At least' two stages of glacial readvances are recognized: The Tjaldanes stage occurred when sea level was between 11 and 22 m and is probably of "Younger Dryas" age; later a readvance occurred in the cirques in the area. On the basis of evidence on cirque distribution, cirque elevation, zeolite zonation, distribution of glacial erosional landscapes, glacial history, marine limits, ice cap profiles and shelf moraine a model of maximum glaciations of Vestfir6ir is proposed: The whole of Vestfir6ir and the surrounding shelf areas was completely ice covered with no ice free areas. Such a stage of glaciation, the Latragrunn stage, probably prevailed in the Vestfiroir area during the last glaciation.

Thesis (M.S.)--Michigan State University. Dept. of Crop and Soil Sciences, 2006. / Title from PDF t.p. (viewed on Nov. 20, 2008) Includes bibliographical references (p. 43-44). Also issued in print.

Thesis (Ph. D.)--University of Washington, 1997. / Vita. Includes bibliographical references (leaves [99]-117).

Thesis (Ph. D.)--University of Alaska Fairbanks, 2005. / "May 2005." Includes bibliographical references. Also available in electronic format via Internet.

Northern peatlands are an important component of the global carbon (C) cycle and have been a net sink of atmospheric C during the Holocene. Under current climate warming conditions, the future sink-source balance of these peatlands is uncertain. In particular, peatlands near the southern limit of permafrost are likely to be sensitive to changes in topography as well as climate. In order to predict how the sink-source balance may change, this thesis focuses on determining the generality of observed patterns of C accumulation in Northeastern Canada. The methodological approach in this thesis is unique. A total of 30 cores were taken from 9 peatlands located in 3 ecoclimatic regions along the North Shore of the Gulf of St Lawrence. This replication of records allows for climate-scale (allogenic) signals to be separated from the internal or local factors (autogenic), and for statistical testing of differences between regions and within sites over time. Trends in carbon accumulation rates (CAR) were analysed on three levels: (1) within individual sites along a hydrological or microtopography gradient, (2) between overall regions located along a climatic or permafrost gradient, and (3) over time on a multi-centennial scale. Lead-210 (210Pb) dating was used throughout the analysis to increase temporal resolution for the last 150-200 years of C accumulation. The method was thoroughly tested from preparation to analysis and found to produce reliable results, comparable with other dating methods. These dates were then used to develop combined age-depth models for longer-term context. Replicated records of 210Pb inventories and fallout rates were also used to address questions of deposition patterns and post-depositional mobility in peat profiles. Total inventories decreased with water table depth, with lichen hummocks having significantly higher inventories. One site also received significantly higher 210Pb deposition than the other two, as it is more sheltered from the Gulf influence. Recent carbon accumulation rates for the 150-year period for all microforms across all regions was 62.1 ± 4.4 g C m-2 a-1, and were highest for Sphagnum hummocks (79.9 ± 8.9 g C m-2 a-1) and lowest for dry lichen hummocks (42.7 ± 6.2 g C m-2 a-1). Patterns and trends at this scale were mainly driven by autogenic processes, including incomplete decomposition in the acrotelm peat. Models of peat accumulation related to acrotelm thickness were found to be overly simplistic, as carbon accumulation for intermediate microforms showed large natural variability driven by changing ecohydrological feedbacks, in part due to permafrost degradation at one of the sites. Over a multi-centennial scale, carbon accumulation rates were driven by a combination of climatic changes and ecohydrological feedbacks due to shifts in the microform configuration in response to permafrost degradation. Changes in carbon accumulation rates were detected and coincided with Little Ice Age temperature/solar minima (including the Spörer, Maunder and Dalton Minima), permafrost degradation since the 1950s, and recent climatic changes in the mid-1990s. Snow cover and exposure of sites and microforms were found to play an important role, rather than solely climatic variables. Rapid Sphagnum re-establishment in post-permafrost degraded features and increasing temperatures meant that carbon accumulation was highest for the northernmost site in the transect. Age-depth models using a combination of lead-210 and radiocarbon dates allowed for the calculation of carbon accumulation rates at a decadal resolution. While peat carbon sequestration is projected to increase in northern regions, the fate of peatland C near the southern limit of permafrost is complex. Future studies seeking to interpret recent changes should include multiple cores and consider both regional climatic and local ecohydrological drivers.