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Peatlands are important sinks and/or sources of carbon, solutes, and elements of potential concern (e.g., Hg, As, Pb, Cu, Zn) to their surrounding environments. Minerogenic permafrost peatlands that receive input of elements from groundwater and weathering of bedrock and surficial materials accumulate substantial amounts of geogenic-derived elements over millennia, which are then frozen in place. As the Arctic cryosphere thaws due to 21st. c climate warming, understanding of permafrost contaminant reservoirs and tracking their release is a growing challenge due to a lack of knowledge on the cumulative and interacting influences of bedrock and surficial geology, vegetation, climate, fire, and ecohydrology on contaminant accumulation in permafrost peatlands. We examined the Holocene history of two permafrost peatlands from the Northwest Territories, Canada, that are underlain by mineralized volcanic and metasedimentary (Daigle Lake peatland) and unmineralized granitoid (Handle Lake peatland) bedrock. Laboratory methods included pyrolytic speciation to determine the quality and quantity of solid organic matter; plant macrofossil and macroscopic charcoal analysis to reconstruct vegetation, peatland development, and fire history; testate amoebae to reconstruct paleohydrological conditions; and inorganic geochemical analyses to determine elemental concentration over time. Both sites have undergone several marked and broadly coincident hydrological shifts and phases of ecohydrological development. During the early Holocene (ca. 8000-5000 cal BP) initial shallow lake environments at both sites transitioned to rich fen and were colonized by Picea. Elevated concentrations of Zn (up to 65 mg.kg-1), Cu (up to 52 mg.kg-1), As (up to 140 mg.kg-1), and Cr (up to 65 mg.kg-1) occur in the basal lacustrine sediments, particularly at the Daigle Lake peatland that is underlain by mineralized bedrock, but become lower in overlying material that accumulated in a fen setting. Depth to water table increased by almost 30 cm in the Handle Lake peatland between ca. 5900 and 4900 cal BP, coincident with the Holocene Thermal Maximum. At this time, local fires were severe and frequent at both sites and associated with elevated Hg (up to 50 µg.kg-1) in the peat. After this dry interval, the water table rose at ca. 3000 cal BP at the Handle Lake peatland and by ca. 2200 cal BP at the Daigle Lake peatland. Fire occurrence declined, coincident with the relatively cool and wet conditions of the Neoglacial interval. A bog was established at both sites between ca. 2700 and 2200 cal BP. Fire occurrence and the concentration of Hg (up to 175 µg.kg-1), As (up to 300 mg.kg-1), and Zn (up to 50 mg.kg-1) have increased over the past 1000 cal yrs, likely due to a combination of anthropogenic input of As and Hg associated with gold mining in the region and global industrialization as well as warming climate and permafrost thaw. This study illustrates the influence of ecohydrology and bedrock geology on the chemical stores of permafrost peatlands.

Aufeis, also known as an icing or naled, is an accumulation of ice that forms primarily during winter when water is expelled onto frozen ground or ice surfaces and freezes in layers. Process‐oriented aufeis research initially expanded in the 20th century, but recent interest in changing hydrological conditions in permafrost regions has rejuvenated this field. Despite its societal relevance, the controls on aufeis distribution and dynamics are not well defined and this impedes projections of variation in aufeis size and distribution expected to accompany climate change. This paper reviews the physical controls on aufeis development, current broad‐scale aufeis distribution and anticipated change, and approaches to aufeis investigation. We propose an adjustment to terminology to better distinguish between the formation process and resulting ice bodies, a clarification of the aufeis classification approach based on source water, and a size threshold for broad‐scale aufeis inventory to facilitate collaborative research. We identify additional objectives for future research including advancing process knowledge at fine spatial scales, describing broad‐scale distribution using current remote sensing capabilities, and improving our understanding and predictive capacity over the interactions between aufeis and landscape‐scale permafrost, hydrogeological, geotectonic, and climate conditions.

Throughout much of northern Canada there is an inadequate knowledge of permafrost and periglacial terrain conditions, which impedes development of climate-resilient northern infrastructure, identification of potential geohazards, decision making regarding resource development, and inferring past and future landscape evolution. Using a land systems approach to better understand formation of landscapes and thaw-sensitive terrains of northern Yukon and northwestern Northwest Territories, we aim to describe the permafrost-related landform-sediment assemblages that exist in the region. Permafrost is continuous in the region, but variations in geology, landscape history, climate, relief, ecology, and other natural processes have produced a diverse range of permafrost conditions and landforms. Using the 875 km-long Dempster and Inuvik-to-Tuktoyaktuk highway corridors (DH-ITH) as a regional transect, and high-resolution satellite imagery, a robust methodology was implemented to identify and digitize (at 1:5000 scale) 8793 landforms (589 km2) within a 10 km-wide corridor (8530 km2) and classify them according to main formational process (hydrological, periglacial, and mass movement). Surficial geology data were extracted from available data sets. Landform densities in all feature classes vary substantially along the transect according to physiographic region and surficial geology. The northern 39% of the corridor is characterized by generally rolling or planar relief, numerous waterbodies (19%), and the remaining land area by mostly morainal (67%), glaciofluvial (12%), lacustrine (7%), and alluvial (7%) deposits. By count, it contains 53% of mapped features and the majority of periglacial (67%) and hydrological (70%) features. In particular, the Tuktoyaktuk Coastlands, Peel Plain, and Mackenzie Delta, contain the greatest density of mapped landforms within the corridor, which cover nearly 23%, 15%, and 15% of the land area of these physiographic regions, respectively. These extents reflect the amount of ground ice and level of permafrost-thaw sensitivity of these regions. In contrast, the physiographic regions of the southern 61% of the study area are characterized by high relative relief, few waterbodies (0.2%), and the land area mainly by colluvial (63%), alluvial (18%), and morainal (14%) deposits. Most mass movement features occur here (85% by count), and are concentrated in the Ogilvie Mountains (n = 1027; 108 km2). This feature inventory provides the basis for developing spatial models of landscape-thaw susceptibility, which can inform risk assessment and improve decision making regarding public safety and environmental management.

The Beaufort Delta region in Northwest Territories, Canada is one of the most rapidly warming areas on Earth. Permafrost thaw and climate change are major stressors on northern infrastructure, particularly in this region which hosts the highest density of Arctic communities and the longest road network constructed on ice-rich permafrost in Canada. The Dempster and Inuvik to Tuktoyaktuk Highways (ITH) comprise a 400-km corridor connecting the region with southern Canada. The corridor delivers a unique opportunity to develop a societally-relevant, northern-driven permafrost research network to encourage collaboration, and support pure and applied studies that engage stakeholders, encourage community participation, and acknowledge northern interests. Successful implementation requires leadership and institutional support from the Government of the Northwest Territories (GNWT) and Inuvialuit and Gwich’in Boards and landowners, and coordination between research organizations including NWT Geological Survey, Aurora Research Institute, Geological Survey of Canada, and universities to define key research priorities, human and financial resources to undertake studies, and protocols to manage data collection and reporting.In 2017, a state of the art ground temperature monitoring network was established along the Dempster-ITH corridor by the GNWT in collaboration with Federal and Academic partners. This network in combination with the maintenance of the Dempster Highway and recent design and construction of the ITH, has created a national legacy of permafrost geotechnical, terrain and geohazard information in this region. The objectives of this program are to integrate old and new data to synthesize physiographic, hydrological, thermal, and geotechnical conditions along the corridor, and to develop applied permafrost research projects that support planning and maintenance of this critical northern infrastructure. In this presentation, we highlight: 1) a collaborative research framework that builds northern capacity and involves northerners in the generation of knowledge and its application to increase community based permafrost monitoring; 2) summaries of existing infrastructure datasets and their foundation for research; and 3) new projects that address emerging climate-driven infrastructure stressors. As the effects of climate change on permafrost environments, infrastructure and communities continue to increase, the need for northern scientific capacity and applied research to support informed decision-making, climate change adaptation and risk management will become increasingly critical. The development of resilient researcher-stakeholder-community relationships is also necessary for the scientific and research initiatives to reach their potential.

The landscape of the Tuktoyaktuk Coastlands, western Canadian Arctic is dominated by glacial and geocryological processes that have modified, imprinted and sculpted the surface, depositing surficial materials upon underlying bedrock. Climate warming continues in this region at a rate that is twice the global average, and retrogressive thaw slump (RTS) activity is increasing. Recently, RTS distribution was associated with glacial limits reached by the Laurentide Ice Sheet and corresponding morainal deposits, but RTS are common in other local terrain units. In this glacial-marginal region, permafrost existed pre-glacially, and non-glacial geomorphic processes occurred throughout the Late Quaternary. Superimposed on these conditions are the effects of thermokarst during the Holocene climatic optimum, followed by a period of cooling. Collectively, these processes and associated forms and deposits have contributed variously to preservation, development, or degradation of permafrost and ground ice. The multifaceted Late Quaternary history in this region has impeded understanding of the distributions of ice-cored topography and RTS. For example, rather than glaciogenic ice, the long reigning regional model for ice-cored topography is according to post-glacial development of intrasedimental segregation-intrusion ice. Toward better understanding the evolution of the whole landscape and the distribution of climate-sensitive terrain, we use a landsystems approach as a means to understand how the ice-cored topography developed where RTS form, through analysing the cryostratigraphy. To this end, we identify 6 RTS representing a suite of ice-cored topographic settings, including: (i) preserved basal glacial ice facies within clayey diamict that has been thrusted and folded by glacial push representing morainal deposits of the Sitidgi Stade; (ii) ice contact outwash sediments associated with the Sitidgi Stade, overlying a thermo-erosional contact with underlying basal glacial icy diamict of the Toker Point Stade; (iii) deformed basal glacial ice, eroded down by meltwater-deposited outwash sands some time between the Toker Point and Sitidgi Stades (could be ca. 12.9 kyr BP); (iv) massive, undeformed segregation-intrusion basal ice, likely formed subglacially by freezing of intrasedimental water in pre-existing Pleistocene sands into the base of the glacier, overlain by glacial diamicton; (v) deformed basal ice facies of intermediate Toker Point – Sitidgi Stades, with an upper layer that may be supra-glacial melt-out till into which segregated ice formed; and (vi) segregation ice that formed as permafrost aggraded into glaciolacustrine clays deposited in proglacial or glacially dammed basins, that was subsequently eroded down by glaciofluvial outwash (Sitidgi Stade). To summarize, the distribution of RTS reflects primarily the distribution of icy basal glacial diamict preserved in moraines, but also basal ice and icy basal diamict that are preserved beneath glaciofluvial deposits, segregation ice in glaciolacustrine deposits, and massive segregation-intrusion ice in Pleistocene sands beneath a till plain.

A peatland from subarctic Canada (Handle Lake 62°29’26.44”N, 114°23’18.23”W) is a degrading permafrost peatland chosen for detailed study due to a legacy of regional arsenic (As) contamination as a result of almost 8 decades of gold mining. The fate of permafrost peatlands and their element stores is unknown due to complex feedbacks between peat accumulation, hydrology, and vegetation that affect redox state and element mobility. We combine palynology with study of plant macrofossils, testate amoebae, organic matter composition, and bulk geochemistry preserved in a ca. 4180-4972 cal year old peat monolith retrieved from the Handle Lake peatland to reconstruct the ecohydrological dynamics to assess future trajectories of permafrost peat, and contaminant storage or release, in response to current and future warming. Sphagnum riparium macrofossils are rare in modern peat habitats and sub-fossils are rare in paleoecological records. Plant macrofossils of this taxon occur in an 11-cm thick layer together with Sphagnum angustifolium between 43 cm (ca. 3390-3239 cal BP) and 25 cm depth (ca. 2755-2378 cal BP) in the monolith. The S. riparium sub-fossils are present with the hydrophilous testate amoebae species Archerella flavum, Hyalosphenia papilio and Difflugia globulosa that are used to quantitatively reconstruct a water table depth of 0-4 cm below the peat surface. Sub-fossils of S. riparium disappear at ca. 2755-2378 cal BP, likely due to an autogenic trophic shift and succession towards more acidophilic conditions favourable to species such as Sphagnum fuscum and Sphagnum russowii. We interpret the occurrence of S. riparium as an indicator of wet and minerotrophic conditions linked to peatland development form rich fen to oligotrophic bog. Because S. riparium is a key pioneer species of disturbed peatlands that have experienced permafrost degradation it will likely be favoured in northern regions experiencing rapid climate warming. In the palynological record the proportion of Sphagnum-type A spores increases (up to 80%) between ca. 3390-3239 cal BP and ca. 2755-2378 cal BP concurrent with a decline in other Sphagnum-type spores. A peak in micro- and macroscopic charcoal occurs between ca. 3557-3286 cal BP and ca. 3275-2771 cal BP, concurrent with a decline in Picea pollen and an increase in Alnus pollen. Regionally, between ca. 3500 and ca. 2500 cal BP Neoglacial climate prevailed with post-Neoglacial warming at ca. 2500 cal BP. It is therefore possible that regional fire occurrence stimulated permafrost degradation at ca. 3500 cal BP. Background As in the active layer monotlith is ~20-30 ppm. The upper 10 cm of the peat are impacted by aerial deposition of As from ore processing and concentrations range up to ~360 ppm. An increase in the concentration of As in the monolith from ~15-20 ppm at the base of the monolith to ~30-40 ppm during this interval may reflect water table depth dynamics that affected the mobility and fate of this redox sensitive element and/or downward mobility from layers impacted by contamination from mineral processing. Degradation of this permafrost within the Handle Lake peatland will release the currently stored As and other contaminants to the regional environment.

Sphagnum riparium (Angstrom) is a rare constituent of modern peatland plant communities and is also very rarely found as a subfossil in peat archives. We present new data on the occurrence of Sphagnum riparium macrofossils in three Northern Hemisphere peatlands from Yellowknife (NW Canada), Abisko (N Sweden), and the Northern Ural Mountains (NW Russia). Sphagnum riparium macrofossils were present in transitional phases between rich fen and oligotrophic bog. Sphagnum riparium was a dominant species in the three sites and was found in combination with Sphagnum angustifolium, Drepanocladus sp., and vascular plants including Andromeda polifolia, Chamedaphne calyculata and Oxycoccus palustris. Testate amoebae indicate that the species occurred in wet to moderately wet conditions (water-table depth inferred from a testate amoeba transfer function model ranged between 25 and 0 cm under the peatland surface). The wet-indicator taxa Archerella flavum and Hyalosphenia papilio dominated the testate amoeba communities in peat horizons containing Sphagnum riparium. The presence of Sphagnum riparium macrofossils in peat profiles in the Northern Hemisphere can be interpreted as an indication of wet minerotrophic conditions, often corresponding to a rise in water-level and establishment of a wet habitat. Sphagnum riparium is a transient species in these peatlands and is replaced by communities dominated by more acidophilic species such as Sphagnum angustifolium, Sphagnum russowii, and Sphagnum fuscum. Our data show that although Sphagnum riparium is a transient peat-forming species, it is widespread in sub-arctic and boreal environments. The subfossil occurrence of Sphagnum riparium in the Northern Hemisphere may indicate that its range has increased during the Late Holocene. The conservation of Sphagnum riparium in peatlands depends on the existence of relatively short-lived transitional communities which potentially can be artificially created.

Contemporary sand wedges and sand veins are active in seasonally frozen ground within the extensive discontinuous permafrost zone in Northwest Territories, Canada. The region has a subarctic continental climate with 291 mm a−1 precipitation, −4.1 °C mean annual air temperature, warm summers (July mean 17.0 °C), and cold winters (January mean −26.6 °C). Five years of continuous observations indicate that interannual variation of the ground thermal regime is dominantly controlled by winter air temperature and snow cover conditions. At sandy sites, thin snow cover and high thermal conductivity promote rapid freezing, high rates of ground cooling, and low near-surface ground temperatures (−15 to −25 °C), resulting in thermal contraction cracking to depths of 1.2 m. Cracking potentials are high in sandy soils when air temperatures are

Icing development in the subarctic Canadian Shield is statistically related to antecedent autumn rainfall and periodic warming intervals in winter. Here, we integrate observations of streamflow, meteorology, and river icing dynamics at the Baker Creek Research Basin, Northwest Territories. We demonstrate that icing development is concordant with winter runoff yield, which is influenced by antecedent autumn rainfall as part of a storage threshold-mediated hydrologic regime that is characteristic of Canadian Shield hydrology. Icing development in Baker Creek typically occurs only if winter runoff is accompanied by frequent warming intervals. Icing dynamics in Baker Creek may now be largely controlled by air temperatures, since runoff in winter has been common since 1997. © 2016 Her Majesty the Queen in Right of Canada Permafrost and Periglacial © 2016 John Wiley & Sons, Ltd.

Lithalsas (ice-cored permafrost mounds) are common within silty clay sediments of the Great Slave Lowland, a low-relief bedrock plain extending to about 50 m above Great Slave Lake, Northwest Territories. Following retreat of the Laurentide Ice Sheet, sediment deposition in the lowland accompanied inundation by glacial Lake McConnell between about 12 700 and 9300 cal BP, and continued subsequently in ancestral Great Slave Lake. Lake-level recession has occurred locally at about 5 mm · a−1 for the last 8000 years, due primarily to isostatic rebound. Maximum limiting ages of permafrost and lithalsas in the lowland are elevation-dependent, being least near the modern shoreline and greater at higher elevations. Many lithalsas, which are up to 8 m high and several hundred metres wide, are less than 3000 years old. They are abundant in alluvium of the Yellowknife River deposited within the last 2000 years, with permafrost aggradation and lithalsa formation continuing in historical time. Copyright © 2016 John Wiley & Sons, Ltd.

Winter roads provide an important transportation service in northern regions. The Tibbitt to Contwoyto Winter Road (TCWR), traversing subarctic Canada, is the busiest heavy-haul road in the world with as many as 10,900 truckloads per season. In addition to lake-ice thickness, trafficability on the TCWR depends upon adequate freezeback of overland portages, which are primarily peatlands underlain by discontinuous permafrost. We investigate threshold requirements for the initiation of winter road operations in this region and assess the use of a recommended 305 °C-day air-freezing index (FDD305a) value as an operational predictor of ground freezing at 30 cm depth, the desired depth to allow winter road construction to commence. Snow compaction and flooding were found to enhance freezeback of portages with early winter overland flow having a similar effect. The majority of winter road portages were not adequately frozen to a depth of 30 cm by FDD305a. Our results indicate that for drained and wet peatlands in this discontinuous permafrost environment, an FDDa threshold of 1100 °C-days is more appropriate than the 305 °C-day threshold. However, TCWR winter road operators presently plan the construction of the winter road by a calendar date rather than by evaluation of the air-freezing index. This practice results in a conservative approach to the start of the construction season, close to 1100 °C-days with a higher percentage of sites frozen to 30 cm depth than would be if the 305 °C-day air-freezing index was used as a guideline. In addition, the use of low-pressure vehicles for snow compaction during the start of the construction season is an effective adaptation practice to accelerate freezing penetration.

Control of absolute stereochemistry in radical and ion radical transformations is a major challenge in synthetic chemistry. Herein, we report the design of a photoredox catalyst system comprised of an oxidizing pyrilium salt bearing a chiral N-triflyl phosphoramide anion. This class of chiral organic photoredox catalysts is able to catalyze the formation of cation radical-mediated Diels-Alder transformations in up to 75:25 e.r. in both intramolecular and intermolecular examples.

Field observations show significant impacts of wildfires on active layer thickness and ground temperatures. However, the importance of fires to permafrost conditions at regional scales remains unclear, especially with climate warming. This study evaluated the regional impacts of fire on permafrost with climate change from 1942 to 2100 using a process-based model in a large subarctic region in the Northwest Territories, Canada. Climate warming is shown to be the dominant factor for permafrost reduction. The warming trend of climate reduces permafrost extent in this region from 67% at present to 2% by 2100. For burned areas, fire increases the reduction of permafrost extent by up to 9% on average, with up to 16% for forest, 10% for tundra and bogs, and 4% for fens. Fire accelerates permafrost disappearance by 5 years on average. The effects of fire on active layer thickness and permafrost extent are much larger in forest areas than in tundra, bogs, and fens. Since active layer is thicker after a fire and cannot recover in most of the areas, the fire effects on active layer are widespread. On average, fires thickens active layer by about 0.5 m. The fire effects on active layer increased significantly after 1990 due to climate warming.

Icings are widespread yet poorly understood winter hydrological phenomena that develop over the winter by freezing successive overflows of groundwater to the surface. Groundwater hydrology in arctic regions is constrained by geological setting and permafrost extent, and overflows are possibly driven by cold winters, winter warming intervals, high antecedent autumn rainfall, and low early winter snowfall. Consequently, icings are spatially recurrent but not necessarily annually nor to the same extent. We test the significance of identified meteorological forcing variables against a long-term data set of icing dynamics and distribution we developed for the Great Slave region around Yellowknife, Northwest Territories. Climate is regionally consistent, but variable geology and permafrost create hydrological conditions representative of much of the subarctic. We mapped 5500 icings in the study area (21,887 km2) with a semiautomated approach utilizing late spring Landsat archival images (1985 to 2014). Individual icing size, ranging 3 orders of magnitude (1.8 × 10−3 km2 to 4.1 km2), is related to return frequency. Infrequent ice (25% return frequency) accounts for 94% of the total icing area (86 km2). Winter warming intervals (≥5°C; typically over 1–3 days) and autumn rainfall (September and October) explain 28% of icing density interannual variation overall. Interannual icing variation and significant meteorological forcing variables differ among ecoregions where varied geological settings and permafrost conditions influence the hydrological regime. Future icings may develop less frequently due to decreasing winter warming intervals, but increasing autumn rainfall may increase icing density where Canadian Shield leads to strong threshold-mediated runoff generation processes.

Permafrost underlies peatlands of the Great Slave region, Northwest Territories, Canada, but permafrost relations beneath other ecotopes of black spruce (Picea mariana), white birch (Betula papyrifera) and mixed forests remain unknown. Permafrost-ecotope relations examined over a 3 year period (2010–13) establish the occurrence and thermal state of permafrost under these different types of forest. Air temperatures and snow depths are regionally consistent. Ground temperature variation primarily reflects latent heat effects during the freezing season, with the duration of season-normalised active-layer freezeback explaining 76% of 1 m ground temperature variation among all sites except xeric peatland. Low apparent thermal diffusivities from substantial latent heat effects strongly attenuate ground temperature variation with depth, and yield zero annual amplitude depths of 7 m or less where annual mean ground temperatures range among sites from -1.4 °C to 0.0 °C. Extensive discontinuous permafrost conditions, related to the extent of forested ecotopes, are commonly in thermal disequilibrium. Whereas permafrost in peatlands may be ecosystem-protected, this represents only about 2% of the area of the region. Permafrost in other forested ecotopes, occurring in ice-rich unconsolidated sediments, is climate-driven and ecosystem-protected because of latent heat effects. Though the rate of permafrost degradation may be reduced, an eventual transition to isolated permafrost retained primarily within ecosystem-driven peatlands implies substantial reductions of permafrost extent in this region. Copyright © 2015 John Wiley & Sons, Ltd.

Technological advances have an important role in the design of greener synthetic processes. In this Personal Account, we describe a wide range of thermal, photochemical, catalytic, and biphasic chemical transformations examined by our group. Each of these demonstrate how the merits of a continuous flow synthesis platform can align with some of the goals put forth by the Twelve Principles of Green Chemistry. In particular, we illustrate the potential for improved reaction efficiency in terms of atom economy, product yield and reaction rates, the ability to design synthetic process with chemical and solvent waste reduction in mind as well as highlight the benefits of the real-time monitoring capabilities in flow for highly controlled synthetic output.

Differential Interferometric Synthetic Aperture Radar (DInSAR) is an increasingly viable method for assessing permafrost terrain stability, but the accuracy and performance within discontinuous permafrost terrain has not been well studied. We used a RADARSAT-2 DInSAR data stack for a 120-day period in the summer of 2010 to map seasonal surface displacement in the discontinuous permafrost terrain of Yellowknife, Northwest Territories. Calculated displacement was compared to surficial geology and municipal land use zones. Displacement results reveal that glaciofluvial, glaciolacustrine, humanly modified, and organic terrain are increasingly unstable, in contrast to predominantly stable bedrock. Within municipal zones, increased proportional displacement is related to higher proportions of glaciolacustrine sediments and organic terrain. Organic terrain, associated with the highest proportion of the moderate downward displacement (−3.0 cm to −6.0 cm), occupies less than 6% of the total area. Widespr...

The Slave Geological Province of the Tundra Shield is a Late Archean craton extending from the north shore of Great Slave Lake in the Northwest Territories to the Coronation Gulf in Nunavut. Underlain by metavolcanic and metasedimentary rocks intruded by granitoid plutons, the region is rich in gold, base metals, and diamonds and hosts numerous historic, active, and prospective mines. Most recently glaciated in the Late Wisconsinan, till and glacifluvial sediments form the most prevalent surficial materials. Glacial landscape features reflect complex ice flow patterns recording several different events. Raised post-glacial marine sediments are significant in the north along the Coronation Gulf at elevations below 200 masl, whereas glacilacustrine sediments related to glacial Lake McConnell are abundant in the south. Ground ice in glacigenic sediments has been preserved since deglaciation as much of the region also lies well within the zone of continuous permafrost. Segregated ice occurs separately within glacimarine and glacilacustrine sediments, and polygonal terrain is abundant on outwash sediments. Glacially derived ground ice includes buried glacial ice within glacifluvial outwash deposits and buried glacial and meltwater ice within eskers. Sediment-rich ice has also been encountered within hummocky till terrain during mine development operations. Surficial features attributed to partial thawing, and creep of massive ground ice, are regionally apparent. Although massive ice has been encountered in only a few locations to date, ground ice may be common within this glaciated region of the Tundra Shield.

The Great Slave Lowland of the Taiga Shield is an 11,000 km2 low-elevation granitic bedrock plain along the north shore of Great Slave Lake, Northwest Territories. It is characterized by a mosaic of coniferous and deciduous forest cover, wetlands, sparsely vegetated bedrock outcrops, and peatlands. The region was glaciated until about 13,000 years ago and then inundated by Glacial Lake McConnell and by ancestral Great Slave Lake, which gradually declined towards the present lake elevation. Consequently, fine-grained glacilacustrine and nearshore lacustrine sediments are broadly distributed across the region. Permafrost is widespread within forest-covered sediments and peatlands, but is not sustained beneath bedrock outcrops, leading to an extensive, but discontinuous, permafrost distribution. Lithalsas, which are permafrost mounds up to 8 m in height and several hundred metres in length, are also abundant. These form by ice segregation within mineral soil, as permafrost aggrades into the fine-grained sediments following lake level recession. Lithalsas are most common within the first few tens of metres above the present level of Great Slave Lake, indicating that many are late Holocene in age and some

Saturated floodplains in Arctic deltas provide conditions favourable for frost mound growth. Little work has been reported from these settings to determine the origin of frost mounds and the controls on their distribution, to assess the longevity of individual mounds, or to quantify variation of mound distribution over time. A case study is presented on low mounds in low-centred syngenetic ice-wedge polygons of Big Lake Delta Plain, outer Mackenzie Delta. In 2008 and 2009, 12 mounds were examined by drilling to describe their morphologic variations and to investigate their growth processes. The mounds, containing a core of ice 15 to 58 cm thick, were less than 1 m high and 3 · 7 to 8 · 5 m in diameter; other mounds were over 10 m long. Organic inclusions in the ice, bubble densities, electrical conductivity profiles, and ice-crystal structure indicated that the mounds were hydrostatic frost blisters. Up to six frost blisters were found within individual polygons due to the relatively small volume of water needed to create each mound. Frost-blister densities, of greater than 1700 km–2, increased toward the wet centres of alluvial islands down gentle topographic gradients. The frost blisters were perennial, with individuals remaining identifiable on aerial photographs and satellite images for up to 10 years. Frost blisters collapsed along dilation cracks opened by hydrostatic uplift and by thawing from their sides caused by snow drifting and water ponding. Cyclical growth and decay of the mounds may degrade the visible polygonal network over time. Copyright © 2013 John Wiley & Sons, Ltd.

A mild and efficient method for the synthesis of novel oxazole, thiazoline, and thiazine derivatives is presented which operates under mild conditions.

A direct method to construct 2-oxazolines and 2-thiazolines from corresponding allylic amides and thioamides is reported. The redox-neutral intramolecular hydrofunctionalization is enabled by a dual catalyst system comprised of 9-mesityl-N-methyl acridinium tetrafluoroborate and phenyl disulphide and exhibits complete selectivity for the anti-Markovnikov regioisomeric products. The cyclization of allylic thioamides is postulated to operate via a modified mechanism in which oxidation of the thioamide, rather than the alkene, is responsible for the observed reactivity.

Field data, remote sensing, and Inuvialuit knowledge were synthesized to document regional ecological change in the outer Mackenzie Delta and to explore the timing, causes, and implications of this phenomenon. In September 1999, a large magnitude storm surge inundated low-lying areas of the outer Mackenzie Delta. The storm was among the most intense on record and resulted in the highest water levels ever measured at the delta front. Synthesis of scientific and Inuvialuit knowledge indicates that flooding during the 1999 storm surge increased soil salinity and caused widespread vegetation death. Vegetation cover was significantly reduced in areas affected by the surge and was inversely related to soil salinity. Change detection analysis, using remotely sensed imagery bracketing the 1999 storm event, indicates severe impacts on at least 13 200 ha of terrestrial vegetation in the outer delta. Inuvialuit knowledge identifying the 1999 surge as anomalous is corroborated by geochemical profiles of permafrost and by a recently published paleo-environmental study, which indicates that storm surge impacts of this magnitude have not previously occurred during the last millennium. Almost a decade after the 1999 storm surge event, ecological recovery has been minimal. This broad-scale vegetation change is likely to have significant implications for wildlife and must be considered in regional ecosystem planning and in the assessment and monitoring of the cumulative impacts of development. Our investigations show that Inuvialuit were aware of the 1999 storm surge and the environmental impacts several years before the scientific and regulatory communities recognized their significance. This study highlights the need for multidisciplinary and locally informed approaches to identifying and understanding Arctic environmental change.

A procedure for the synthesis of oxazolidinone and tosyl enamines is reported. Alkynoyl oxazolidinones and tosyl imides undergo reaction to form enamines in the presence of catalytic amounts of tertiary amines. The data suggest that an amide anion is formed during the reaction, which undergoes conjugate addition to form the final product.