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Boundaries between air masses, called frontal zones, have been associated with vegetation boundaries (Bryson, 1966; Hare and Ritchie, 1972). Using gridded climate reanalysis data, we analyze the air masses and frontal zones of North America. The position of the July Arctic front varies significantly through the period 1948-2007, with a mean position similar to that found by Bryson (1966). The variability of the front position can be associated with changes in the general circulation; when the AO and SOI are positive (negative), the position of the July Arctic front is further north (south). There is also more variability in the July Arctic front position in Eastern versus Western Canada. When the July Arctic front is north (south) of the mean position, the boreal forest and tundra vegetation is more (less) productive. There is some evidence that climate warming is only starting to shift the July Arctic front to the north. / This study was funded by the Natural Sciences and Engineering Research Council (NSERC) and the Polar Climate Stability Network (PCSN) project funded by the Canadian Foundation for Climate and Atmospheric Sciences (CFCAS).

Recent successful drilling operations at Lake El'gygytgyn, NE Russia have recovered sediment cores back to 3.6Ma, representing the longest time-continuous sediment record of past climate change in the terrestrial Arctic. Analysis of the hydrogen isotopic ratio (δD) of specific organic biomarkers allows reconstruction of past hydrological conditions, thereby providing a powerful tool for reconstructing past Arctic climate changes. Compound specific isotopic analysis of sedimentary lipids from this remote basin provides new insights into the climate evolution of the Arctic, capturing the mechanisms and dynamics of the last two glacial-interglacial transitions, potentially enhancing the accuracy of modeled future climate change projections and presenting an opportunity to estimate past polar amplification of climate change. The results of this research document the first continuous, high fidelity continental record of reconstructed δD in precipitation from terrestrial plant leaf waxes in the High Arctic spanning the last 120 ka. The hydrogen isotopic composition of lipid biomarkers were determined from previously obtained Lake El'gygytgyn sediment cores and compared with other multi-proxy evidence of past climate change within the lake basin. The modern isotope hydrology and controls on the δD lipid signal were first established within the El'gygytgyn Basin from modern precipitation, stream and lake waters, ice cover as well as modern vegetation, water column and lake bottom surface sediments in order to provide a modern context to properly constrain and interpret paleoclimatic proxy data. Reconstructed δD records of paleoprecipitation and temperature at Lake El'gygytgyn lead other northern hemisphere climate records (e.g. North Greenland Ice Core Project, NGRIP δ18O records) and are in phase with other continental and Antarctic climate records, suggesting early high northern latitude continental warming prior to established glacial-interglacial transitions. The data set generated here leads to multiple avenues of future work and provides critical insights into Arctic paleoclimate and paleohydrology, contributing to our understanding of high latitude environmental change over geological timescales. Collectively, the results of this dissertation research will provide a context for paleoclimate reconstructions and future organic geochemical and stable isotope analysis. Future application of compound-specific H isotope analyses to long drill cores (recovered in 2009; ~315m of sediment) will potentially provide a quantitative high-resolution record of paleoclimatic and paleoenvironmental changes spanning the last 3.6 Ma.

Lake Tuborg is a large lake on west-central Ellesmere Island, Nunavut. Part of the lake is meromictic, and contains trapped saltwater below about 55 m depth. The lake receives meltwater and sediments from multiple sources, including snowmelt and glacier melt. A lake process study was undertaken from 2001-2003 at Lake Tuborg that involved obtaining profiles of water temperature, salinity, transmissivity, and dissolved oxygen. Networks of short and long sediment cores were also obtained throughout the lake. During the last year of monitoring the lake and its sediments, a large catastrophic drainage of an ice-dammed lake occurred (a jökulhlaup). This was the largest jökulhlaup witnessed in Canada since 1947. Detailed measurements of lake conditions before, during, and after the jökulhlaup allowed the responses to be measured in great detail. The lake drained by floating its ice dam, an extremely rare drainage style in the Canadian High Arctic. The basin of Lake Tuborg closest to jökulhlaup inflow filled with fresh, cold and turbid water. A sill separates this basin from the larger more distal meromictic basin, and this sill effectively blocked turbidity currents from entering this basin. Conclusions from this phase of research include (1) salinity and temperature in the saltwater basin were minimally affected by the jökulhlaup, and (2) at a deep, distal location, an identifiable thick, coarse-grained, non-erosive deposit was produced by the jökulhlaup. The above conclusions allowed the varved sedimentary record to be examined for similar deposits in the past, with the assumption that similar deposits could be found in the long core record, the sediments could be dated, and that previous jökulhlaup deposits would also be nonerosive. Varve-thickness counting, Cesium-137 dating, and particle size analyses showed that prior to 1960, no similar events occurred in roughly the last thousand years. In addition, only three large jökulhlaups have occurred in the last thousand years, all of which occurred after about 1960. This significantly improves the understanding of the history of the lake, the surrounding glaciers, and the paleoclimate of the region. The lake bottom deposits that were sampled before, during and after the 2003 jökulhlaup were extraordinarily unique. A major part of the work of characterizing these deposits involved determining the size of their constituent particles. Image analysis of sedimentary particles using backscattered electron microscope imagery is a method to determine particle size at extremely high resolution. This tool improves on existing techniques since it automates the process of statistically processing images, quantifies the percentage of disturbances on images, and allows for extremely small measurement windows relative to particle size by implementing special particle counting rules.

Retrogressive thaw slumps (RTSs) are thermokarst landforms that develop on slopes in permafrost regions when thawing permafrost causes the land surface to collapse. RTSs are an indicator of climate change and pose a threat to human infrastructure and ecosystems in the affected areas. As the availability of ready-to-use high-resolution satellite imagery increases, automatic RTS mapping is being explored with deep learning methods. We employed a pre-trained Mask-RCNN model to automatically map RTSs on Banks Island and Victoria Island in the western Canadian Arctic, where there is extensive RTS activity. We tested the model with different settings, including image band combinations, backbones, and backbone trainable layers, and performed hyper-parameter tuning and determined the optimal learning rate, momentum, and decay rate for each of the model settings. Our final model successfully mapped most of the RTSs in our test sites, with F1 scores ranging from 0.61 to 0.79. Our study demonstrates that transfer learning from a pre-trained Mask-RCNN model is an effective approach that has the potential to be applied for RTS mapping across the Canadian Arctic.

<p> In 1978, the water balance of a small lake near Resolute, N.W.T. was studied. Using measured water inputs and water outputs, the change in storage term was calculated. A positive net change in storage was partitioned between storage in the active layer and storage in the lake.</p> <p> A comparison of the magnitudes of the various components of the water balance equation shows that i) for the snow-dammed lake, outflow is most important for the few days following the breakup of the channel, ii) evaporation is an important process, removing almost as much water as summer precipitation received by the basin, and iii) depending on the condition of the active layer during freeze-up, considerable amounts of water may be held in storage at the end of summer.</p> / Thesis / Bachelor of Arts (BA)

Migratory animals face numerous challenges that are often exacerbated by climate change. In the Arctic, where climate change is occurring at 4x the average global rate, species must adapt rapidly to novel conditions. I studied four species of sea ducks (Long-tailed Ducks Clangula hyemalis and Steller’s Polysticta stelleri, Spectacled Somateria fischeri, and King Eiders S. spectabilis), of which Steller’s and Spectacled Eiders are federally Threatened, and all are well below historic population sizes. I conducted three studies to assess how female sea ducks interact with their habitats between arrival on the breeding grounds and nesting. First, I assessed patterns of occurrence within diverse tundra wetland types by female sea ducks, in relation to three metrics of wetland resource availability: wetland surface area and biomass in benthic cores and emergent sweeps separately. I also monitored activity budgets of female sea ducks. Wetlands containing the emergent grass Arctophila fulva were highly selected for by all species relative to the wetland surface area and biomasses of prey, while large lakes, streams, and wetlands lacking Arctophila were avoided. Most time was allocated towards foraging or loafing, emphasizing the importance of energy acquisition during this transitional time period following migration and prior to nesting. Wetlands selected for broadly across species are under threat as climate change reduces the prevalence of these wetland types on the landscape, requiring adaptation to such novel conditions. My second study assessed how sea ducks rely upon prey resources within tundra wetlands, and upon stored tissues acquired in marine habitats. Female sea ducks must both produce eggs and sustain themselves throughout a ~30-day period from egg-laying through hatch, with potentially different nutrient sources for each aspect of the reproductive process. I sampled stable isotopes of proteins in egg membranes (reproductive endpoint) and in red blood cells (body maintenance endpoint), which I modeled relative to stable isotopes in a suite of prey taxa from freshwater tundra ponds and marine habitats. Across all four species, most proteins came from tundra wetlands (≥ 89% of modeled protein sources) for egg production. Smaller-bodied long-tailed Ducks and Steller’s Eiders relied heavily on the local environment for body maintenance and survival (red blood cells) during incubation, but larger Spectacled and King Eiders only gained ~60% of proteins locally, relying on the remaining 40% from body tissues acquired previously from marine habitats. Local wetlands provided 60-99% of proteins for female sea ducks. Freshwater habitats in which sea ducks forage warrant protection, and conservation for some species requires interagency cooperation across tundra, freshwater wetlands, and marine habitats. My third study assessed patterns of nest site selection across species, years, and spatial scales. How females choose nest sites has major implications for population processes. Decisions integrate information across spatial scales for each component of habitat a hen considers. I used boosted regression trees (a machine learning technique) to model suitability of nesting habitat for 414 variables of habitat features at six spatial scales. Social association with other ducks were highly important in determining suitability. Suitable habitat varied spatiotemporally among species, but the relative amount of suitable habitat was consistent across years for each species. Conservation for suitable habitat must include broad areas to incorporate interannual variability. Through these three studies, I assessed the relative use of; importance of; and reliance upon various wetland types, the relative importance of marine versus freshwater nutrients for reproduction, and the factors driving nest site selection in a guild of sea ducks facing imminent climate change.

As our climate continues to shift, it is fundamental to understanding these unprecedented changes through field research done in biomes most critically impacted. Due to the remoteness and extreme climatic nature of these research stations, they are typically either hastily built flat pack constructions or sterile pill boxes with little consideration of the immediate surrounding. This investigation looks at structuring the restrictions of environment to give the architecture a sense of place, rather than looking at these extremes as limitations. This proposal is sited in the Alaskan Arctic circle, where research is being conducted to understand the intertwined issues of climate change and permafrost melt. It is the intent of this project to present a prototype of a responsible and responsive architecture for Toolik Station, Alaska,a renowned destination for arctic climate research. This thesis synthesizes unpredictable site and environmental factors, elements which will become increasingly commonplace as our planet's climate shifts. The proposal for the Northern Reach interrogates and responds: How are we best equipped to live and work in a rapidly changing measure of extremes? What imbues an architecture with a sense of place when that place is inherently mercurial? / Master of Architecture / To best understand the unprecedented effects of climate change on critical, research is often conducted in remote and often extreme areas of the planet, where the living conditions are less than ideal which affects the longevity and effectiveness of said research. This project investigates the extremes of living and working as a field scientist in Toolik Station, Alaska, and proposes housing and accommodations which are more sensitive and appropriate for its site than what is currently being used. The proposed project can be used as a prototype to replace other buildings at the chosen site.

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