The Permafrost Map of Canada shows the region of Labrador in northeast Canada as spanning conditions from continuous permafrost in the north to isolated patches in the south. However, few studies have documented this and the most detailed field information comes from research in the 1960s and 1970s, with contemporary permafrost distribution largely unexamined. An extensive investigation of contemporary permafrost conditions throughout Labrador and portions of northeastern Québec was undertaken between 2013 and 2017 to fill this knowledge gap. A multi-scale approach to analyzing permafrost distribution was employed, including collection of detailed field information at selected sites, establishment of climate and ground monitoring apparatus at more than 35 different locations and spatial numerical permafrost modelling of permafrost conditions across the region. Spatio-temporal infilling was used with thin plate spline interpolation to generate temporally-consistent climate grids for 1948-2016 at a monthly resolution for all of Labrador-Ungava. Evaluation of derived air temperature grids against meteorological observations and remote field monitoring stations showed an overall accuracy of 0.8 ± 0.3 °C on a monthly timescale. The grids were used to generate freezing and thawing degree-days maps to facilitate permafrost modelling. Field investigations in the coastal barrens of southeastern Labrador (51.5°N to 54°N) used geophysics (DC electrical resistivity tomography), standard field methods and ground temperature monitoring to characterize very isolated patches of permafrost observed to be up to 8 m thick beneath palsas and peat plateaus. Permafrost was inferred to be absent in wetland, forested and forest-tundra areas inland, notwithstanding average air temperatures lower than at the coast. However, field investigations undertaken farther north in the coastal community of Nain, NL (56.3°N) showed permafrost to be present at numerous sites within the community in tundra, forested and disturbed settings. Boreholes and geophysics showed permafrost less than 20 m thick at several locations including beneath existing and proposed building locations. These investigations of permafrost along a latitudinal gradient highlight the contrasting permafrost environments found in coastal regions of Labrador. Field data from monitoring stations across Labrador (n=83) were used to analyze the interrelationships of key variables in permafrost modelling. Snow depth, not mean annual air temperature, was the strongest single determinant of mean temperatures at the ground surface and at ~1 m depth. Ground temperature variability was most related to land cover class with a critical late-winter snow depth of 70 cm or less inferred to be sufficient to prevent the formation of permafrost at the monitoring sites. Testing of several different land cover datasets for permafrost model parameterization gave errors in ground surface temperature ranging from ±0.9 to ±2.1°C. A new estimate of the distribution of permafrost at high resolution (250 m x 250 m) was generated for all of Labrador-Ungava using a modified version of the temperature at the top of permafrost model. Predicted ground temperatures for long-term climate normal ranged regionally from -9°C (for high elevations in northern Québec) to +5°C (for southeastern Labrador-Québec). Modelling of permafrost for specific temporal windows (1948-1962; 1982-1996; 2000-2014) suggested that permafrost area increased from the middle of the 20th Century to a potential peak extent (36% of the total land area) in the 1990s. Subsequent warming is predicted to have caused a decrease in permafrost extent of one-quarter (95 000 km2) even if air temperatures rise no further, providing air and ground temperatures equilibrate. The field observations in this thesis validated research conducted in the interior of Labrador during 1970s which directly linked permafrost presence or absence to snow thickness. Permafrost was more widespread than would be expected in coastal areas based on the region’s mean annual air temperatures which suggests that specific geomorphologic and meteorological settings may allow permafrost to persist in otherwise unsuitable regions. Land cover type, through its influence on snow distribution, was shown to be a key variable whose changes must be considered when examining future permafrost conditions in the region.

The internal structure of periglacial landforms contains valuable information on past and present environmental conditions. To benefit from this archive, however, an enhanced understanding of subsurface variations is crucial. This enables to assess the influence of the internal structure on prevailing process regimes and to evaluate the sensitivity of different landform units to environmental changes. This thesis investigates structural variations in the subsurface of (i) rock glaciers,(ii) solifluction lobes, (iii) palsas/ lithalsas and (iv) patterned ground, which occur between the different landform types, but also between landform units of the same type. Investigated variables comprise (i) the spatial distribution of permafrost, (ii) ground ice content, (iii) the origin of ground ice, (iv) thickness of the active layer and (v) frost table topography. Multi-dimensional investigations by the geophysical methods Electrical Resistivity Imaging (ERI) and Ground-Penetrating Radar (GPR) were performed in six study areas (a–f): four of them are located in high-alpine environments in Switzerland and two of them are located in the subarctic highlands of Iceland. Additionally, surface and subsurface temperature values were continuously recorded at selected study sites. At one study site, pF-values, representing the matric potential (or water potential), were recorded. From a methodological view, this thesis focuses on the application of quasi-3-D ERI, an approach in which many two-dimensional data sets are combined to create one three-dimensional data set. This permits e.g., a three-dimensional delimitation of subsurface structures and a spatial investigation of the distribution of ground ice. Besides the analysis of field data, this thesis incudes a comparison between inversion models produced with different software products, based on two synthetic data sets. The detection of resistivity structures and reflection patterns provides valuable insights into the internal structure of the investigated landform units: At the high-alpine study site at (a) Piz Nair, a highly variable ice content indicates a complex development of the investigated rock glacier assembly. The local formation of ground ice is attributed to an embedding of surface patches of snow or ice into the subsurface by rockfall. Results of geoelectric monitoring surveys on selected rock glaciers show the influence of seasonal alterations in the internal structure on subsurface meltwater flow. At the study site at (b) Piz Üertsch, results indicate the occurrences of isolated ground ice patches in a significantly larger rock glacier. Detected characteristics of the internal structure enable to reconstruct the development of the rock glacier, in which a temporary override of an adjacent glacier tongue on the rock glacier is considered crucial for the current distribution of ground ice. However, results of this thesis clearly show the absence of buried glacier ice in the subsurface of the rock glacier. Results from a rock glacier near the (c) Las Trais Fluors mountain ridge affirm the existence of a water-permeable frozen layer, which was assumed in previous studies. Furthermore, results show that the rock glacier contains large amounts of rockfall deposits. A joint interpretation of ERI and GPR results from the investigated scree slope at the mountain (d) Blauberg (Furka Pass) reveals characteristic structures in the subsurface, which enable a differentiation between solifluction lobes and pebbly rock glaciers. At the subarctic study site (e) Orravatnsrústir, results show that the internal structure of palsas can be used to deduce their current development stage and to assess past and future developments. Presented results affirm a long history of palsa development at the study site, as assumed in previous studies, but indicate recently changing environmental conditions. The investigated occurrences of patterned ground in the proglacial area of the glacier (f) Hofsjökull are currently not influenced by the detected occurrence of permafrost, according to the presented results. Therefore, a temporary formation of pattered ground is assumed, which is linked to the retreat of the glacier. This thesis shows discrepancies between the internal structure of some of the investigated landform units and the recent environmental conditions. This indicates a delayed adaption and a low sensitivity of the landform units to environmental changes. Findings indicate that the future development of permafrost will be strongly affected by variations in snowfall. Furthermore, the detection of isolated occurrences of ground ice at several study sites contradicts the widely assumed effectivity of balancing heat fluxes to create homogenous subsurface conditions in relatively fine-grained subsurface materials. / Der strukturelle Aufbau periglazialer Landformen beinhaltet wertvolle Informationen über vergangene und heutige Umweltbedingungen. Um diese Informationen nutzen zu können, muss jedoch ein vertieftes Verständnis für den Zustand der inneren Struktur und möglicher Variationen entwickelt werden. Dieses Wissen ermöglicht beispielsweise eine Abschätzung des Einflusses der inneren Struktur auf das momentan dominierende Prozess-Regime und eine Beurteilung der Sensitivität gegenüber sich verändernden Umweltbedingungen. Die vorliegende Arbeit untersucht Unterschiede im Aufbau von (i) Blockgletschern, (ii) Solifluktionsloben, (iii) Palsas/ Lithalsas und (iv) Frostmusterböden, die zwischen den Landformtypen, aber auch zwischen einzelnen Einheiten desselben Typs bestehen. Betrachtet werden dabei (i) die räumliche Verbreitung von Permafrost,(ii) der Eisgehalt im Untergrund, (iii) die Entstehung von Untergrundeis, (iv) die Mächtigkeit der Auftauschicht sowie (v) die Formung der Frosttafel. In sechs Untersuchungsgebieten (a–f), davon vier in Hochgebirgsregionen der Schweiz und zwei im subarktischen Hochland Islands, wurden Untersuchungen mittels mehr-dimensionaler geophysikalischer Verfahren, Widerstandsgeoelektrik (ERI) und Bodenradar (GPR), durchgeführt. Zudem wurden an ausgewählten Standorten kontinuierlich Temperaturwerte der Oberfläche und des Untergrunds aufgezeichnet. An einem Standort wurden ergänzend pF-Werte, die die Saugspannung des Porenwassers angeben, aufgezeichnet. Methodischer Schwerpunkt der vorliegenden Arbeit ist die Anwendung von quasi-3-D ERI, einem Ansatz bei dem Datenpunkte mehrerer zweidimensionaler Datensätze zu einem dreidimensionalen Datensatz vereinigt werden. Dies erlaubt beispielsweise eine dreidimensionale Abgrenzung von Untergrundstrukturen und damit eine räumliche Untersuchung der Verbreitung von Untergrundeis. Ergänzend zur Arbeit mit Felddaten enthält die vorliegende Arbeit einen Vergleich zwischen Inversionsmodellen, die auf Basis von zwei identischen, synthetischen Datensätzen mit unterschiedlichen Softwareprodukten generiert wurden. Durch die Detektion von Widerstandsstrukturen und Reflektionsmustern lassen sich wertvolle Erkenntnisse über den strukturellen Aufbau der untersuchten Einheiten gewinnen: Im hochalpinen Untersuchungsgebiet am (a) Piz Nair weisen stark schwankende Eisgehalte auf eine komplexe Entwicklungsgeschichte der untersuchten Blockgletschergruppe hin. Die lokale Entstehung von Untergrundeis wird auf Verschüttungen oberflächlicher Schnee- oder Eisfelder durch Steinschlag zurückgeführt. An einem Blockgletscher der Gruppe wird mittels geoelektrischer Wiederholungsmessungen der saisonale Einfluss der inneren Struktur auf den Schmelzwasserabfluss im Untergrund durch Veränderungen der Permafrosttafel gezeigt. An einem deutlich größeren Blockgletscher im Untersuchungsgebiet am (b) Piz Üertsch zeigen die Ergebnisse dieser Arbeit isolierte Vorkommen von Untergrundeis. Hier kann anhand der inneren Struktur die Entwicklung des Blockgletschers nachvollzogen werden, wobei insbesondere eine zeitweilige Überdeckung des Blockgletschers durch eine benachbarte Gletscherzunge als ausschlaggebend für die lokale Verteilung von Untergrundeis angesehen wird. Die Ergebnisse zeigen, dass kein Gletschereis in den Block gletscher eingebettet wurde. Die vorgestellten Ergebnisse der Untersuchungen an einem Blockgletscher nahe des Bergkamms (c) Las Trais Fluors bestätigen die dort in vorherigen Studien angenommene Wasserdurchlässigkeit der Frosttafel. Zudem zeigt der Aufbau des Blockgletschers das Auftreten großer Mengen von Steinschlagablagerungen. Am untersuchten Schutthang am (d) Blauberg (Furkapass) können durch eine gemeinsame Auswertung der Ergebnisse von ERI und GPR charakteristische Strukturen detektiert werden, durch die sich die dort auftretenden Lobenstrukturen in Solifluktionsloben und Feinmaterial-Blockgletscher (Pebbly Rock Glaciers) unterscheiden lassen. Im subarktischen Untersuchungsgebiet (e) Orravatnsrústir zeigen die Ergebnisse, dass vom strukturellen Aufbau von Palsas auf deren gegenwärtiges Entwicklungsstadium geschlossen werden kann und dass Rückschlüsse auf vergangene und zukünftige Entwicklungen möglich sind. Die vorgestellten Ergebnisse bestätigen die in vorherigen Studien getroffene Annahme einer lange zurückreichenden Entwicklungsgeschichte der Palsas, weisen aber auch auf sich seit kurzem verändernde Umweltbedingungen hin. Die untersuchten Frostmusterböden im Gletschervorfeld des (f) Hofsjökull zeigen gegenwärtig keine Beeinflussung durch Permafrost, obwohl ein rezentes Vorkommen von Permafrost angenommen wird. Daher wird eine temporäre Bildung der untersuchten Oberflächenstrukturen angenommen, die an den Rückzug des Gletschers gebunden ist. Die vorliegende Arbeit zeigt, dass die innere Struktur einiger der untersuchten Landform-Einheiten Diskrepanzen zu den momentanen Umweltbedingungen aufweist. Dies deutet auf eine geringe Sensitivität, beziehungsweise eine verzögerte Anpassung der Landschaftsformung auf sich verändernde Umweltbedingungen hin. Des Weiteren zeigt die vorliegende Arbeit, dass besonders Veränderungen im Schneedeckenauf- und abbau wesentlich zur zukünftigen Entwicklung von Permafrost in den untersuchten Gebieten beitragen werden. Die Beobachtung isolierter Vorkommen von Untergrundeis in mehreren Untersuchungsgebieten steht in Kontrast zur verbreiteten Annahme, dass die ausgleichende Wirkung von Wärmeströmen im Untergrund in feinkörnigem Material besonders stark ist / Periglacial environments are facing dramatic changes. Warming air temperatures and strong snow cover variations fundamentally affect landforming processes in this hotspot region of Climate Change. But before we can assess the response of landform development to a changing climate, we need to enhance our understanding of the internal structure of those landforms. Within this study, a broad scope of landform types from alpine and subarctic regions is investigated: rock glaciers, solifluction lobes, palsas and patterned ground. By using the geophysical methods 2-D and 3-D ERI, as well as GPR surveying, structural differences and similarities between landform units of different or the same landform types are highlighted. This enables a reconstruction of their past and a projection of their future development.

No description available.

The rate of biodegradation of hydrocarbon contaminated soils can be studied using the radiocarbon (14C) content of CO2 efflux from the ground surface over an impacted area.14C is used as a tracer to distinguish modern 14C CO2 from natural respiration processes and 14C depleted CO2 derived from petroleum degradation. Studies have shown that this analysis provides reliable, quantifiable data and an effective means of correcting for background CO2 which may present some natural depletion from older subsurface organics. The study area for this project is a remote community in Northern Yukon where organic rich sediments overlying continuous permafrost are contaminated by diesel oil. An objective of this study was to evaluate the use of 14C to quantify background CO2 in permafrost soils with abundant, older labile organics. A second objective was to test a new sampling technique to facilitate sample shipment from remote sites, which traps soil CO2 in small sealed exetainers as a solid barium carbonate. Data obtained from established radiocarbon sampling procedures and this new novel approach were shown to be comparable and reproducible. This technique facilitated both sample collection and shipment as well as analysis by accelerator mass spectrometry (AMS), allowing for rapid, efficient sampling techniques to be deployed in remote areas. Results of this study show the carbonate method to be an economical and effective sampling method, and used at the Old Crow site, demonstrated that under current climate conditions, older organics in the subsurface do not confound the use of 14CO2 for source zone biodegradation assessment at this hydrocarbon impacted permafrost site.

The circumpolar Arctic is experiencing dramatic environmental changes that are already impacting tundra ecosystems and northern communities that are intimately linked to the land. Increasing permafrost degradation, shrub encroachment, larger and more frequent fires, and increasing human development have significant effects on biotic and abiotic conditions in the lower Peel River watershed, NT. To understand and respond to rapid environmental changes, diverse knowledge perspectives are needed, so my M.Sc. research uses scientific and social scientific approaches to investigate environmental change in the lower Peel River watershed. I investigated the impacts of the Dempster highway on plants, soils and permafrost in the Peel Plateau by conducting field surveys at sites dominated either by tall alder (Alnus crispa) shrubs or by dwarf shrubs, at 30 m and 500 m from the highway. At each site I measured vegetation composition, alder growth, soil nutrients, litter and organic layer thickness, active layer thickness, and snow depth. We found that alder growth and recruitment were enhanced adjacent to the Dempster Highway, and dramatic alterations to plant community composition, soil properties and ground temperatures were observed where alder shrubs had formed closed canopies. Tall shrub sites adjacent to the road exhibited lower abundance of understory vegetation including mosses, greater litter and organic soil thickness, higher nutrient availability, and deeper snowpack. Biotic and abiotic changes associated with road effects feedback with alder canopy development, and have important implications for permafrost conditions adjacent to the roadbed, and potentially on road bed performance. This research contributes to our understanding of environmental changes caused by the highway and their consequences for infrastructure stability and pan-Arctic changes in vegetation cover. In a separate but complementary effort, I worked with Teetl’it Gwich’in land users and youth from Fort McPherson, NT to map observations of environmental conditions and changes. In the pilot year of a community-based environmental monitoring program, we employed participatory multimedia mapping with Teetl’it Gwich’in land users and youth from Fort McPherson, NT. I accompanied Gwich’in monitors on trips on the land to document environmental conditions and changes. Observations made by land users were documented using photos, videos and audio taken by youth, and land users provided detailed information about each observation in follow-up interviews. I compiled observations (photo/video, GPS location, and interview audio and transcript) into a web-based map where the public will be able to see changes on the land in the images and words of Gwich’in land users. The online map will provide a medium for local residents to communicate their knowledge and concerns about the environment, and will be useful for land management and planning, environmental monitoring, and adaptation. / Graduate / 0768 / 0329 / 0326 / hkgill@uvic.ca

Northern regions account for approximately 30% (1035 Pg) of the world’s soil organic carbon (SOC). Much of this carbon is currently stored in permafrost soils, which are vulnerable to increasing air and ground temperatures. Permafrost landscapes rich in ground ice, such as high-centred polygonal terrain, are likely to be highly vulnerable to thaw. Degradation of ice wedges in high-centred polygonal terrain causes increased moisture and ground temperatures. These environmental controls are likely to have a large impact on carbon cycling in this terrain type. My M.Sc. research combined both lab and field-based analyses to investigate current and potential carbon emissions from high-centred polygonal terrain in the Tuktoyaktuk Coastlands. To estimate the magnitude of future emissions from this terrain type I incubated six permafrost cores collected at two sites. Peat cores from four depths were each incubated under four conditions (cold anaerobic, warm anaerobic, cold aerobic, warm aerobic). The observation that carbon mineralization rates do not vary with depth demonstrates that the soil carbon liberated from permafrost in high-centred polygonal terrain will not be limited by SOC quality. This experiment also shows that emission rates will be moderated by temperature and moisture levels, and will be primarily in the form of CO2. To examine the impact of ice-wedge thaw on carbon emissions in high-centred polygonal terrain, we combined opaque chamber measurements of flux and estimates made from water samples using a gas diffusion model. Field sampling at two sites contrasted carbon emissions from polygon centres (n=18), wet troughs (n=18) and ponds (n=20). We also measured ground temperature and soil moisture using thermistors and a moisture sensor. Our field results demonstrate that ice-wedge degradation results in increased ground temperature, deeper active layers, and increased CO2 and CH4 emissions. Contrary to our expectations, CO2 emissions were not limited by waterlogged conditions, demonstrating the importance of anaerobic CO2 production. Our field measurements demonstrate that increasing temperatures are correlated with rising CO2 emissions in aerobic environments, and rising CO2 and CH4 emissions in anaerobic environments. Taken together, these two studies demonstrate that as ground temperatures increase in high-centred polygonal terrain, carbon emissions from ecosystem respiration are likely to increase. / Graduate / 0481 / 0425 / 0768

No description available.

No description available.

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 cycling of water in the landscape is influenced by climate change on different time scales and in different directions regarding warming or cooling trends. Along with a changing climate, also the landscape and subsurface conditions, such as permafrost extent, may change in a long-term perspective. Permafrost and hydrology are intimately connected but the interactions between them are poorly understood, and the hydrological response to climate change is complex. The first part of this thesis investigates the effects of different drivers of future changes in hydrological flow and water storage components in the present day temperate Forsmark catchment in Sweden. The role of taliks and their influence on the exchange of deep and shallow groundwater in permafrost environments are also studied. This is done by a simulation sequence where the site is exposed to the landscape, climate and permafrost changes expected from site-specific numerical modeling. In the second part of this thesis, present day periglacial hydrological processes are studied in the Two Boat Lake catchment in western Greenland by field and model investigations of the site. The presence of a through talik below the Two Boat Lake, and data from a deep bedrock borehole into the talik, enable studies of the hydrological interactions between the lake and the talik. The spatial and temporal variability of the different water balance components of the catchment are quantified and the interactions between the surface water and the supra- and sub-permafrost groundwater are analyzed. The results show that the investigated changes in climate and permafrost influence hydrology more than the investigated landscape changes. Under permafrost conditions, the general direction of the exchange between deep and shallow groundwater may change relative to unfrozen conditions. The simulation studies of Forsmark show that the relative topography between taliks governs the recharging and discharging conditions, which is consistent with results from Two Boat Lake. The lake is located at high altitude relative to other taliks and hydraulic measurements indicate recharging conditions. The talik recharge is small compared to other water balance components and does not influence the lake level, which instead is found to be controlled by evapotranspiration and water inflow from the active layer. This is concluded from numerical simulations that take into account and combine evapotranspiration with other surface and subsurface hydrological processes. This thesis highlights the need to integrate surface and subsurface process modelling in order to quantitatively understand and represent the dynamics and complexity of hydrological interactions in periglacial catchments.