Glaciers of southwestern Yukon (Canada) and southeastern Alaska (USA) are presently experiencing high rates of annual mass loss. These high melt rates have mainly been investigated with respect to regional temperature trends, but comparatively little is known about how climate variations regulate snow accumulation on these glaciers. This study examines the synoptic weather patterns and air flow trajectories associated with extreme snowfall events in the central St. Elias Mountains (Yukon). The analyses are based on data retrieved from an automated weather station (AWS) between 2003 and 2012, which provide the longest continuous records of surface meteorological data ever obtained from this remote region. The AWS data reveal that 47 extreme snowfall events (> 27 cm per 12 hours) occurred during this period, of which 79 % took place during the cold season months. Air flow trajectories associated with these events indicate that a vast majority had their origin in the North Pacific south of 50°N. Less frequent were air masses with a source in the Aleutian Arc/Bering Sea region and the Gulf of Alaska, and in a few rare cases precipitating air was traced to continental source regions in Western Canada and Alaska. Composite maps of sea-level pressure and upper-level winds associated with extreme snowfall events revealed a frequent synoptic pattern with a low-pressure area centered over the Kenai Peninsula (Alaska), which drives strong southerly winds over the Gulf of Alaska towards the St. Elias Mountains. This pattern is consistent with AWS data wind recordings during snow storms. The most typical synoptic configurations of the North Pacific low-pressure area during extreme snowfall events are either elongated, split, or single-centered, and these situations represent possible seasonal analogues for the different states of the Aleutian Low in the subarctic North Pacific. However, neither the geographical position or intensity of negative sea-level pressure anomalies, nor surface pressure gradients associated with extreme snowfall events are good predictors of the actual snowfall SWE amounts recorded in the central St. Elias Mountains. Estimated snowfall and total precipitation gradients with altitude were confirmed to be much steeper (by up to ~30 %) on the continental side (Yukon), than on the coastal side (Alaska) of the St. Elias Mountains, reflecting the strong orographic division between the continental and coastal marine climatic regimes. Finally, patterns of 500-mb geopotential height anomalies associated with extreme snowfall events at Divide were compared with those associated with unusually high accumulation years in an ice core from the nearby Eclipse Icefield. Results confirm previous findings that associate high snow accumulation winters in this region with the presence of a strong dipole pressure structure between western North America and the Aleutian Low region, a structure which resembles the positive phase of the Pacific North American atmospheric circulation pattern. / De höga smälthastigheter som uppmätts på glaciärer i S:t Eliasbergen (Yukon, Kanada) har främst undersökts utifrån regionala temperatureffekter, men hur storskaliga (synoptiska) klimatvariationer reglerar snöackumulation på dessa glaciärer är mindre känt. Denna analys belyser synoptiska mönster och rekonstruerade banor av luftmassor i samband med extrema snöfall i den centrala delen av S:tEliasbergen. De iakttagelser som gjorts i denna studie bygger på data som hämtas från automatiserade väderstationer (AWS) mellan 2003 och 2012, vilka ger den längst sammanhängande dokumentationen av markmeteorologisk data som någonsin erhållits från denna plats.AWS data avslöjar att 47 extrema snöfall (>27 cm per 12 timmar) inträffade på glaciären under denna period, varav 79 % ägde rum under den kalla årstiden. I samband med dessa snöfall visar det sig att en stor majoritet av luftmassebanorna hade en utgångspunkt i norra Stilla havet söder om 50°N. Mindre vanligt var att luftmassor utgick från Aleuterna/Berings hav och Alaskabukten, och i några sällsynta fall spårades luftmassorna till kontinentala utgångspunkter i västra Kanada och Alaska. Luftmassebanorna från norra Stilla havet visade främst syd-nordcykloniska luftflöden, medan luftmassorna från Aleuterna/Berings hav och Alaskabukten indikerade väst-öst cykloniska luftflöden. Sammansatta kartor indikerade ett likartat synoptiskt mönster av ett lågtryckscentrum över Kenaihalvön (Alaska) för dessa tre marina källområden. Lågtrycket drev starka sydliga cykloniska vindar över Alaskabukten mot S:tEliasbergen och detta vindmönster överensstämde med AWS data. De typiska synoptiska situationerna i samband med extrema snöfall kännetecknades antingen av ett långsträckt, ett delat eller ett litet lågtryckscentrum. Dessa kunde kopplas till olika möjliga tillstånd av det Aleutiska lågtrycket i norra Stilla havet. Studien kunde inte bekräfta att lågtryckscentrums geografiska placering, anomalier av havsnivåtryck eller tryckgradienten starkt reglerade de extrema snöfallmängderna uppmätta från AWS data på studieplatsen. De beräknade nederbördsgradienterna bekräftades vara brantare på den kontinentala sidan (Yukon) än på kustsidan (Alaska) av S:tElias-bergen, vilket återspeglade skillnader mellan den kontinentala och den kustnära marina klimatzonen. Slutligen jämfördes avvikande geopotentiella höjdmönster i samband med extrema snöfall med tidigare studieresultat av extrem snöackumulation i isborrkärnor från den intilliggande glaciären Eclipse. Resultaten indikerar att dessa mönster delvis korrelerade till tidigare resultat och bekräftar förekomsten av en liknande dipol-tryckstruktur mellan västra Nordamerika och Aleuterna.

Permanent electrode arrays were set up at ten monitoring sites from Whitehorse, Yukon, to Fort St. John, British Columbia, in order to gain a clearer perspective of the effectiveness of electrical resistivity tomography (ERT) monitoring over an annual cycle of freezing and thawing. This research forms part of a longer-term project that is attempting to use ERT to examine changes in permafrost resulting from climate change. Inter-site and intra-site variability were examined by installing and maintaining data-loggers to monitor active layer and shallow permafrost temperatures, air temperatures, and snow depths at each site from August 2010 – August 2011. Additional site information was collected on each ERT survey date, including frost table depths, snow depths, and vegetation heights. Based on nearby community records, the climate in the region has been warming by a rate of 0.3 to 0.5 °C per decade since 1970. The permafrost at all ten sites was characteristic of sporadic discontinuous and isolated patches permafrost zones, and is classified as Ecosystem-protected. Nine of the ten permafrost sites had permafrost that was thinner than the 14 or 7 m penetration depth of the ERT survey (three-layer system consisting of an active layer, permafrost, and sub-permafrost perennially unfrozen zone). The most predictable results were achieved at the two-layer system site (active layer overlying permafrost to the base of the profile) in each of its virtual resistivity boreholes, relative resistivity change comparisons, and mean near-surface apparent resistivity progressions. ERT is an effective method of delineating permafrost boundaries in thin permafrost environments and does show strength when monitoring areas of seasonally frozen ground. Repeat surveys at a site indicate seasonal changes in three-layer conditions, but not as predictably as those in a two-layer system. In order to receive the most accurate information regarding permafrost extent and thickness, it appears ideal to conduct ERT surveys annually, within the same month as the previous year’s survey.

In this thesis, I describe three experimental studies that investigate the hotly debated role of competition in structuring communities in unproductive habitats. The studies were done in a boreal forest understory plant community in the southwestern Yukon. The first study was a traditional neighbour removal experiment. Ten of the most common species were transplanted as seedlings into transects with and without neighbours in a factorial design with two levels of water addition and two levels of fertilizer addition. The presence of neighbours increased survival and biomass of 6 species indicating a facilitative effect of neighbouring plants. The second study used the Community Density Series (CDS) methodology. The first of these was a 10-speciesexperimental community established from seed and grown in sandboxes at 6 densities with 2 watering levels and 2 fertilizer levels in a factorial design. At the community level, density dependence was observed at all life stages, but was not consistently competitive or facilitative - both emergence and final per plant shoot mass were density dependent, while survival to the end of the season was inversely density dependent. The effect of water was positive at seed emergence whereas fertilizer negatively affected survival. Species specific responses were also dependent on life stage. The final study was a 4-year CDS in the field using 9 common understory species at 6 densities and 3 fertilizer levels. Density negatively affected the community every year except for the first with competition being important at all densities above x1/8th the average community density. Constant final yield was reached in plots above the naturalx1 density for the last two years of the study. Responses to density were species-specific and 7 species declined with increasing density. No facilitative effects were observed. These studies demonstrate that density dependence is important in structuring this unproductive boreal understory habitat. The CDS approach allows us to quantify both the intensity and importance of plant competition at the community and species levels and to determine whether the importance of these biotic interactions depend on abiotic factors. The results clearly show that species-specific responses to biotic interactions are not necessarily the same as community level responses and if we are to understand community structure, it is necessary to use appropriate methodologies.

Permanent electrode arrays were set up at ten monitoring sites from Whitehorse, Yukon, to Fort St. John, British Columbia, in order to gain a clearer perspective of the effectiveness of electrical resistivity tomography (ERT) monitoring over an annual cycle of freezing and thawing. This research forms part of a longer-term project that is attempting to use ERT to examine changes in permafrost resulting from climate change. Inter-site and intra-site variability were examined by installing and maintaining data-loggers to monitor active layer and shallow permafrost temperatures, air temperatures, and snow depths at each site from August 2010 – August 2011. Additional site information was collected on each ERT survey date, including frost table depths, snow depths, and vegetation heights. Based on nearby community records, the climate in the region has been warming by a rate of 0.3 to 0.5 °C per decade since 1970. The permafrost at all ten sites was characteristic of sporadic discontinuous and isolated patches permafrost zones, and is classified as Ecosystem-protected. Nine of the ten permafrost sites had permafrost that was thinner than the 14 or 7 m penetration depth of the ERT survey (three-layer system consisting of an active layer, permafrost, and sub-permafrost perennially unfrozen zone). The most predictable results were achieved at the two-layer system site (active layer overlying permafrost to the base of the profile) in each of its virtual resistivity boreholes, relative resistivity change comparisons, and mean near-surface apparent resistivity progressions. ERT is an effective method of delineating permafrost boundaries in thin permafrost environments and does show strength when monitoring areas of seasonally frozen ground. Repeat surveys at a site indicate seasonal changes in three-layer conditions, but not as predictably as those in a two-layer system. In order to receive the most accurate information regarding permafrost extent and thickness, it appears ideal to conduct ERT surveys annually, within the same month as the previous year’s survey.

The Hopper property is located in the Yukon Tanana terrane in the southwestern Yukon. It is characterized by granodiorite-hosted copper and molybdenum mineralization that is related to propylitic alteration and shearing. The focus of this study is to develop a genetic model for the copper mineralization based on field, petrographic and geochemical analyses. The mineralization zone is roughly 500 m long and 20 m wide and is hosted in a granodiorite of calc-alkaline affinity interpreted to be part of the Ruby Range batholith which intruded the Aishihik metamorphic suite. The intrusion took place during the late Cretaceous based on U and Pb analyses of zircons with laser ablation inductively-coupled plasma mass spectrometer, placing it in the same time frame as the intrusion hosting the Casino mineralization, the largest porphyry copper deposit in the Yukon. The mineralization consists of chalcopyrite and molybdenite found along fractures, as disseminations and on shearing surfaces. Sulphur isotopes from chalcopyrite and pyrite range from -1.7 to -0.8 per mil suggesting it is ortho-magmatic in origin. The chemical compositions of biotite and amphibole of the Hopper intrusion resemble mineral chemistry of known porphyry systems. Biotites from both Hopper and Casino exhibit Mg-Cl avoidance and have similar values of MnO, TiO2, Al2O3, BaO, Na2O and K2O, and amphiboles range in composition between magnesio-hornblende and actinolite, similar to other porphyry copper type deposits. There are two distinct populations of titanite in the Hopper intrusion, magmatic and hydrothermal. Magmatic titanites are euhedral and are in sharp, planar contact with other magmatic phases, whereas hydrothermal titanites are anhedral and are associated with alteration minerals and the mineralization. Both populations show substitution between Ti and Al+Fe+Nb+Zr+Ce+Y. The hydrothermal titanites are richer in Ti, Cu, and Cr compared to the magmatic ones that are more enriched in Mo suggesting the mineralization is ortho-magmatic in origin. Sulphur isotopes analyses suggest Hopper could be a porphyry type mineralization. However, the mineralization was also found to be related with propylitic alteration, shearing and depletion in Si and K, indicating this is not a typical system. Therefore, two possible models can explain the copper occurrence at Hopper. According to the first model, the mineralization is ortho-magmatic and is part of a porphyry system, but it has been remobilized to the propylitic zone. A second model is that the mineralization is much younger than the intrusion and is related to shearing.

The importance of integrating technology across the curriculum has been prominent in educational literature for the past decade. Numerous obstacles have been identified and documented surrounding the successful integration of technology in public schools. Access to hardware, appropriate software, professional training for educators, technical and financial support to sustain meaningful uses of technology in schools are the primary areas to be addressed when designing a comprehensive information technology implementation strategy for educational environments. The obstacles are clear, but many educational leaders have failed to develop a model which successfully addresses the challenge of integrating the use of technology as a tool for teaching and learning and as a means of constructing new knowledge for and by students. This paper will explore how technology facilitates learning through inquiry and how inquiry supports a constructivist/constructionist approach to teaching and learning for students and professional staff. This will lead to an examination of how inquiry and constructivism advance the integration of technology in education and how it provides a venue for developing communities of inquiry in schools. A framework for two initiatives developed for Yukon schools will be presented which address many of the challenges common to the successful integration of technology in public schools today. Both initiatives, the Computer Resource Teacher Model (CRTM) and Technology Learning Communities (TLC), promote integrative and constructive uses of technology through an inquiry-based approach to teaching and learning with computers.

This project examines arsenic in plants growing near closed or reclaimed gold mines located in the traditional territories of two Yukon First Nations. A total of 238 soil and plant samples (comprising 9 different species) were collected from Mt. Nansen, Arctic Gold and Silver, and Venus Mine tailing properties. At each property, samples were collected near the suspected point source of contamination, approximately 1 -3 km away, and from background sites. Species were chosen for their ethnobotanical significance to the Little Salmon/Carmacks and the Carcross/Tagish First Nations, based on interviews with Elders and other knowledgeable people. Total and inorganic arsenic concentrations were determined using ICP-MS and AAS instrumentation, and organic arsenic concentrations were calculated from the difference. Uptake of arsenic by plants was low compared to soil arsenic concentrations. In both plants and soil, the arsenic form was predominantly inorganic. Concentrations in berries at all three sites were low or undetectable, and are therefore considered safe to eat under Health Canada tolerable daily intake guidelines for inorganic arsenic. At Mt. Nansen, the lichen "caribou moss" (Cetraria/Cladina spp.), Bolete mushrooms (Leccinum spp.), and the medicinal shrubs willow (Salix spp.) and Labrador tea (Ledum groenlandicum/L. decumbens spp.) had high mean arsenic concentrations around point sources or at sites up to 1.5 km away. These localized high concentrations will not likely affect foraging animals, given their constant movement. However, Carmacks residents could avoid gathering all species with elevated arsenic around the Mt. Nansen mining property until reclamation is complete.

In this thesis, I describe three experimental studies that investigate the hotly debated role of competition in structuring communities in unproductive habitats. The studies were done in a boreal forest understory plant community in the southwestern Yukon. The first study was a traditional neighbour removal experiment. Ten of the most common species were transplanted as seedlings into transects with and without neighbours in a factorial design with two levels of water addition and two levels of fertilizer addition. The presence of neighbours increased survival and biomass of 6 species indicating a facilitative effect of neighbouring plants. The second study used the Community Density Series (CDS) methodology. The first of these was a 10-speciesexperimental community established from seed and grown in sandboxes at 6 densities with 2 watering levels and 2 fertilizer levels in a factorial design. At the community level, density dependence was observed at all life stages, but was not consistently competitive or facilitative - both emergence and final per plant shoot mass were density dependent, while survival to the end of the season was inversely density dependent. The effect of water was positive at seed emergence whereas fertilizer negatively affected survival. Species specific responses were also dependent on life stage. The final study was a 4-year CDS in the field using 9 common understory species at 6 densities and 3 fertilizer levels. Density negatively affected the community every year except for the first with competition being important at all densities above x1/8th the average community density. Constant final yield was reached in plots above the naturalx1 density for the last two years of the study. Responses to density were species-specific and 7 species declined with increasing density. No facilitative effects were observed. These studies demonstrate that density dependence is important in structuring this unproductive boreal understory habitat. The CDS approach allows us to quantify both the intensity and importance of plant competition at the community and species levels and to determine whether the importance of these biotic interactions depend on abiotic factors. The results clearly show that species-specific responses to biotic interactions are not necessarily the same as community level responses and if we are to understand community structure, it is necessary to use appropriate methodologies.

The Hopper property is located in the Yukon Tanana terrane in the southwestern Yukon. It is characterized by granodiorite-hosted copper and molybdenum mineralization that is related to propylitic alteration and shearing. The focus of this study is to develop a genetic model for the copper mineralization based on field, petrographic and geochemical analyses. The mineralization zone is roughly 500 m long and 20 m wide and is hosted in a granodiorite of calc-alkaline affinity interpreted to be part of the Ruby Range batholith which intruded the Aishihik metamorphic suite. The intrusion took place during the late Cretaceous based on U and Pb analyses of zircons with laser ablation inductively-coupled plasma mass spectrometer, placing it in the same time frame as the intrusion hosting the Casino mineralization, the largest porphyry copper deposit in the Yukon. The mineralization consists of chalcopyrite and molybdenite found along fractures, as disseminations and on shearing surfaces. Sulphur isotopes from chalcopyrite and pyrite range from -1.7 to -0.8 per mil suggesting it is ortho-magmatic in origin. The chemical compositions of biotite and amphibole of the Hopper intrusion resemble mineral chemistry of known porphyry systems. Biotites from both Hopper and Casino exhibit Mg-Cl avoidance and have similar values of MnO, TiO2, Al2O3, BaO, Na2O and K2O, and amphiboles range in composition between magnesio-hornblende and actinolite, similar to other porphyry copper type deposits. There are two distinct populations of titanite in the Hopper intrusion, magmatic and hydrothermal. Magmatic titanites are euhedral and are in sharp, planar contact with other magmatic phases, whereas hydrothermal titanites are anhedral and are associated with alteration minerals and the mineralization. Both populations show substitution between Ti and Al+Fe+Nb+Zr+Ce+Y. The hydrothermal titanites are richer in Ti, Cu, and Cr compared to the magmatic ones that are more enriched in Mo suggesting the mineralization is ortho-magmatic in origin. Sulphur isotopes analyses suggest Hopper could be a porphyry type mineralization. However, the mineralization was also found to be related with propylitic alteration, shearing and depletion in Si and K, indicating this is not a typical system. Therefore, two possible models can explain the copper occurrence at Hopper. According to the first model, the mineralization is ortho-magmatic and is part of a porphyry system, but it has been remobilized to the propylitic zone. A second model is that the mineralization is much younger than the intrusion and is related to shearing.

Valley glaciers often occur within complex dendritic systems where tributary glaciers contribute ice mass and blocking potential to the trunk glacier. Analysis of glacier inventories and maps in the regions of Svalbard, East Greenland, Yukon Territory and the Thompson Glacier system indicates that trunk - tributary intersections commonly occur at angles between 45° and 90°. An analogue material with flow properties similar to creep in pure ice has been used to simulate flow in a model valley glacier. The model and a series of blockages were constructed based on dimensions derived from the inventory and map analysis. The angled blockage indicates lower overall velocity rates and appears to have a funnelling rather than blocking affect on the analogue material. The perpendicular obstruction that blocked half the width of the model valley caused a piling up of analogue material prior to a release into the unobstructed side of the valley. / ix, 149 leaves : ill. ; 29 cm.