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Permafrost and Periglacial Processes

Wiley Online Library : Permafrost and Periglacial Processes

Published: 2017-07-01T00:00:00-05:00


Permafrost Thaw and Liberation of Inorganic Nitrogen in Eastern Siberia


The currently observed climate warming will lead to widespread degradation of near-surface permafrost, which may release substantial amounts of inorganic nitrogen (N) into arctic ecosystems. We studied 11 soil profiles at three different sites in arctic eastern Siberia to assess the amount of inorganic N stored in arctic permafrost soils. We modelled the potential thickening of the active layer for these sites using the CryoGrid2 permafrost model and representative concentration pathways (RCPs) 4.5 (a stabilisation scenario) and 8.5 (a business as usual emission scenario, with increasing carbon emissions). The modelled increases in active-layer thickness (ALT) were used to estimate potential annual liberation of inorganic N from permafrost soils during the course of climate change. We observed significant stores of inorganic ammonium in permafrost, up to 40-fold higher than in the active layer. The modelled increase in ALT under the RCP8.5 scenario can result in substantial liberation of N, reaching values up to the order of magnitude of annual fixation of atmospheric N in arctic soils. However, the thaw-induced liberation of N represents only a small flux in comparison with the overall ecosystem N cycling. Copyright © 2017 John Wiley & Sons, Ltd.

Pleistocene Involutions and Patterned Ground in France: Examples and Analysis Using a GIS Database


A georeferenced database is used to analyse the distribution of Quaternary soft-sediment deformation structures across France. They include features visible in aerial photographs (soil stripes and cells) and features described in cross-section (involutions). Overall, there is no clear relation between the distribution of features and the locations of known faults and earthquakes in available databases. In contrast, the distribution agrees with that of Pleistocene periglacial structures. Most of the soil stripes and cells are located north of 47.5°N, i.e. in the zone of ice-wedge pseudomorphs, and can be interpreted as deformation structures of an active layer in permafrost terrain. The height of the involutions is influenced by the nature of the filling, the substrate and latitude. Deformation structures are larger in coarse material, reflecting the role of drainage and thermal conductivity. Their height increases northward to ca. 2 m at 48°N. This is thought to reflect the increase in thickness of the layer subjected to freeze–thaw cycles. Bowl-shaped structures separated by coarse pillars, which correspond to soil stripes seen in section, have formed on slopes in settings unfavourable to the generation of high pore-water pressure. Their genesis is probably related to differential frost heave. Ball-and-pillow structures and diapirs are common in flat and poorly drained terrain, and formed by liquefaction and sometimes fluidisation in a periglacial setting. Copyright © 2017 John Wiley & Sons, Ltd.

Palaeoenvironmental Proxies for Permafrost Presence During the Younger Dryas, Central Poland


Involutions and small frost fissures have been recorded over a wide area of the lower terrace of the Warta River valley (central Poland). They developed at the lithological boundary between an organic-rich deposit with a thin peat layer (unit b) and an underlying fluvial sandy deposit (unit a). Most of the involutions are products of a reversed density gradient and loading, or developed under the influence of cryohydrostatic pressure. Among them are drop-like and flat-bottomed structures, diapirs, flame-like and fold structures and irregular involutions. Some frost fissures have also been recorded in the same stratigraphic position. The sedimentological properties and formative mechanism of the involutions, together with environmental data (lithology, groundwater conditions, snow cover and vegetation), reveal their origin as periglacial. Radiocarbon dating indicates that the structures formed during the Younger Dryas. Overall, the involutions and frost fissures indicate that permafrost re-aggraded in this region of central Poland during the Younger Dryas. Copyright © 2017 John Wiley & Sons, Ltd.

State of High-Altitude Permafrost on Tropical Maunakea Volcano, Hawaii


One of the most unusual occurrences of sporadic permafrost is on the summit plateau of Maunakea volcano on Hawaii Island, where permafrost was documented in two cinder-cone craters in the 1970s. To investigate the state of this permafrost, we acquired multi-year ground temperature data and conducted electrical resistivity and ground penetrating radar surveys. The two ice bodies still exist, but one has shrunk in volume by an order of magnitude and is expected to disappear soon. The other is still more than 50 m wide. We also prospected the summit region for additional permafrost bodies, based on insolation modelling, temperature probing and geomorphological indicators, but none was found. Permafrost occurs preferentially in the interiors of craters with a closed basin, even though there are exterior slopes that receive less solar radiation annually. Copyright © 2017 John Wiley & Sons, Ltd.

Effect of Climate on Morphology and Development of Sorted Circles and Polygons


Sorted circles and polygons are widespread features of periglacial landscapes, but the controls on their development remain poorly understood, impeding their use as palaeoenvironmental indicators. We investigate the relationship of sorted circles and polygons to altitude in the northern Billefjorden area, central Svalbard. The patterns occur in two distinct elevation zones, below 200–250 m asl and above 600 m asl. The higher-elevated patterns have smaller diameters and shallower sorting depths due to a thinner active layer at higher elevations, suggesting that sorted patterns can indicate climate conditions and ground thermal state when the patterns initiated. Geology is believed to be of less importance for pattern morphology in the study area, causing only its fine-scale variations. The pattern diameter-to-sorting depth ratios have a median value of 3.57, consistent with previous studies and theoretical models of patterned-ground formation involving circulation mechanisms. Large-scale sorted patterns may develop over centennial timescales in this high-Arctic environment. They are probably not in equilibrium with present-day climate conditions and have probably formed throughout the Holocene. Copyright © 2017 John Wiley & Sons, Ltd.

Cryostratigraphy and the Sublimation Unconformity in Permafrost from an Ultraxerous Environment, University Valley, McMurdo Dry Valleys of Antarctica


The cryostratigraphy of permafrost in ultraxerous environments is poorly known. In this study, icy permafrost cores from University Valley (McMurdo Dry Valleys, Antarctica) were analysed for sediment properties, ground-ice content, types and distribution of cryostructures, and presence of unconformities. No active layer exists in the valley, but the ice table, a sublimation unconformity, ranges from 0 to 60 cm depth. The sediments are characterised as a medium sand, which classifies them as low to non-frost susceptible. Computed tomography (CT) scan images of the icy permafrost cores revealed composite cryostructures that included the structureless, porous visible, suspended and crustal types. These cryostructures were observed irrespective of ground-ice origin (vapour deposited and freezing of snow meltwater), suggesting that the type and distribution of cryostructures could not be used as a proxy to infer the mode of emplacement of ground ice. Volumetric ice content derived from the CT scan images underestimated measured volumetric ice content, but approached measured excess ice content. A palaeo-sublimation unconformity could not be detected from a change in cryostructures, but could be inferred from an increase in ice content at the maximum predicted ice table depth. This study highlights some of the unique ground-ice processes and cryostructures in ultraxerous environments. Copyright © 2017 John Wiley & Sons, Ltd.

Recent Increases in Permafrost Thaw Rates and Areal Loss of Palsas in the Western Northwest Territories, Canada


Decay of palsas can indicate permafrost status, particularly in regions where air temperatures have increased rapidly in recent decades. Using weather data, annual surveys of active-layer thickness, and analyses of high-resolution aerial imagery from the eastern Selwyn/western Mackenzie Mountains, NT, Canada, we show that permafrost temperatures have increased, active layers have deepened, and palsa areal extents have decreased considerably since the 1940s. High-altitude palsas thawed quickly from the 1940s to the 1980s, although some low-altitude palsas have recently decreased rapidly in areal extent due to peat-block calving. The linear rate of increasing active-layer thickness may not be congruent with the non-linear rate of areal loss of palsas. The rapid and episodic collapse of palsas at some sites highlights the necessity to consider hydrology, vegetation cover, landscape position, and morphology in palsa dynamics in addition to a warming climate. Copyright © 2017 John Wiley & Sons, Ltd.

Factors Controlling Velocity Variations at Short-Term, Seasonal and Multiyear Time Scales, Ritigraben Rock Glacier, Western Swiss Alps


This study analyses the factors controlling variations in short-term, seasonal and multiyear deformation velocity of an alpine rock glacier from data obtained over periods of 1–20 years. The Ritigraben rock glacier, in the western Swiss Alps, was monitored using tacheometry, terrestrial laser scanning, an in situ global positioning system and borehole deformation measurements. Rock glacier stratigraphy and ground temperature data were obtained from boreholes, and long-term meteorological data (temperature, precipitation, snow water equivalent) from nearby weather stations. Shearing within a distinct water-bearing layer represents the major component of the displacement. Short-term accelerations and seasonal velocity patterns of the rock glacier deformation appear to have been triggered by water supply to this layer. A long-term acceleration of the rock glacier was probably also caused by increased water supply. Permafrost temperature in the rock glacier has increased slightly since 2002, yet no direct causality could be established between this limited warming and rock glacier acceleration. Copyright © 2017 John Wiley & Sons, Ltd.

Path-Dependent Frost-Wedging Experiments in Fractured, Low-Permeability Granite


To investigate the mechanism of frost wedging in fractured low-porosity bedrock, we monitored the opening of an artificial 4 mm wide and 80 mm deep crack, cut 20 mm from the end of a rectangular granite block. Two freezing protocols were employed – top-down and bottom-up, the former consisting of short- and long-term variants, lasting 1 and 53 days, respectively. Our results demonstrate that (i) in 1-day experiments, maximum crack widening during top-down freezing is around 0.11 mm, while bottom-up freezing produces only 0.02 mm of deformation; (ii) neither ice nor water pressure causes measurable irreversible crack widening during 1-day tests; (iii) irreversible crack widening is only observed following the 53-day experiment under top-down freezing. Based on these results, we suggest (i) freezing direction plays a key role in determining the magnitude of crack widening; and (ii) freezing duration could be essential for crack propagation. The fracturing is both time-dependent and subcritical; thus, persistent freezing in winter could actually be the active period of crack propagation. This allows us to propose a simplified method to calculate ice pressure according to crack widening. Here we show how freezing direction and duration in ice-filled cracks control the path-dependent efficacy of frost-wedging. Copyright © 2017 John Wiley & Sons, Ltd.

Vegetation Succession, Carbon Accumulation and Hydrological Change in Subarctic Peatlands, Abisko, Northern Sweden


High-resolution analyses of plant macrofossils, testate amoebae, pollen, mineral content, bulk density, and carbon and nitrogen were undertaken to examine the late Holocene dynamics of two permafrost peatlands in Abisko, Subarctic Sweden. The peat records were dated using tephrochronology, 14C and 210Pb. Local plant succession and hydrological changes in peatlands were synchronous with climatic shifts, although autogenous plant succession towards ombrotrophic status during peatland development was also apparent. The Marooned peatland experienced a shift ca. 2250 cal yr BP from rich to poor fen, as indicated by the appearance of Sphagnum fuscum. At Stordalen, a major shift to wetter conditions occurred between 500 and 250 cal yr BP, probably associated with climate change during the Little Ice Age. During the last few decades, the testate amoeba data suggest a deepening of the water table and an increase in shrub pollen, coinciding with recent climate warming and the associated expansion of shrub communities across the Arctic. Rates of carbon accumulation vary greatly between the sites, illustrating the importance of local vegetation communities, hydrology and permafrost dynamics. Multiproxy data elucidate the palaeoecology of S. lindbergii and show that it indicates wet conditions in peatlands. Copyright © 2017 John Wiley & Sons, Ltd.

Utilising a Suite of Isotopic and Elemental Tracers to Constrain Cryoturbation Rates and Patterns in a Non-sorted Circle


The empirical quantification of rates of material movement in cryoturbated soils has lagged behind the physical and chemical characterisation of these materials. We applied a novel suite of elemental (C, Hg), stable isotope (13C) and radioisotope (137Cs, 210Pb, 14C, 10Be) tracers in conjunction with analytical and numerical models to constrain the rates and patterns of soil movement due to cryoturbation in a non-sorted circle (NSC) near Abisko, Sweden. We present the first observations of the variability of 10Be across a patterned-ground feature, which facilitate the interpretation of subsurface peaks in soil organic carbon, Hg and 13C and provide constraints on the surficial histories of cryoturbated materials. Apparent rates of surficial lateral movement across the NSC estimated from 137Cs and 210Pb (0–2.55 cm year−1) decreased with distance from its centre and were an order of magnitude greater than rates of subduction and subsurface movement estimated from 14C (0.04–0.27 cm year−1). Novel estimates of the original surficial residence times of cryoturbated parcels based on excess 10Be and Hg inventories ranged from 238 to 3940 years. Our results demonstrate the utility of the spatially explicit application of elemental and radioisotopic tracer suites to constrain cryoturbation rates in Arctic patterned ground. Copyright © 2017 John Wiley & Sons, Ltd.

Microtextural Inheritance on Quartz Sand Grains from Pleistocene Periglacial Environments of the Mazovian Lowland, Central Poland


Sand grains from Quaternary glacial, aeolian and fluvial deposits in the Mazovian Lowland, central Poland, were examined to characterize the effects of different Quaternary processes on sand-grain surfaces that experienced repeated cycles of intense polar-desert-like conditions during the Middle and Late Pleistocene. A cold, dry and windy periglacial environment prevailed here at least twice between the Saalian (Marine Isotope Stage (MIS) 6) and Holocene (MIS 1) stages. Because the surface characteristics of quartz sand grains can provide important palaeoenvironmental information, we examined grains extracted from sediment samples in different landforms to determine their surficial features from scanning electron microscope images. The grain surfaces were dominated by microtextures characteristic of aeolian-induced grain transformation, indicated by a high percentage of well-rounded, low-relief-worn grains with dish-shaped depressions, bulbous edges and upturned plates. Although remnants of previous sedimentary cycles were occasionally observed, aeolian effects were dominant even in glacial and fluvial settings. Quartz microtextures indicated that none of the examined grains represented their original setting, but rather suggested remobilisation under periglacial conditions. Copyright © 2017 John Wiley & Sons, Ltd.

Very Large Cryoturbation Structures of Last Permafrost Maximum Age at the Foot of Qilian Mountains (NE Tibet Plateau, China): a Discussion


Intensely cold conditions occurred during part of the last major glaciation of the mountains and Qinghai–Tibet Plateau in northeast China but their chronology is constrained by few limiting ages. At the Mengyuan section, on the northeastern margin of the Qilian Mountains, sandy silt provided three OSL ages that suggest deposition during a very cold, dry period in northeastern China between c. 29 and 19 ka (early part of marine isotope stage (MIS) 2). Load-casting into the underlying outwash gravel occurred during climate amelioration. In some cases, the sandy silt infilled the spaces left by underlying thawing blocks of ice without collapse of the surrounding gravel. The gravel must therefore be older than c. 30 ka and was probably deposited by outwash from glaciers on the higher parts of the Qilian Mountains during MIS 3. Included in them were buried contemporaneous or remnant blocks of glacial ice. Subsequently the surface became flat by unknown processes and was finally covered by a thin loess dating from 2.7 ka, indicating it was deposited in the first warmer period in the Neoglacial sequence of events. Thus, the last major cold event spanned the period through isotope stages 2 and 3 in this area (57 to c. 19 ka), during which the dominant effects of glaciation of the mountain tops were replaced by intensely dry, cold permafrost conditions for c. 10 ka. Copyright © 2017 John Wiley & Sons, Ltd.

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Reconstructing Periglacial Geomorphology: The Contribution of J. Ross Mackay


Ross Mackay's contributions to periglacial geomorphology are commonly regarded as the fruit of solo inspiration. In fact, his work is an exemplary product of its time. At the outset of his career, geomorphology was entering a radical transformation from interpretive study of landscape history towards quantitative study of landscape-forming processes. Early periglacial geomorphology was concerned mainly with attempting to infer historical environmental conditions on the periphery of the great Pleistocene ice sheets and Mackay's earliest works are historically oriented accounts of regional geography. From 1960, however, his work, following the new perspective, was based on quantitative measurement of landforms and land-forming processes, both in the field and on maps, and application of physical theory to interpret his observations. He focused attention on individual periglacial landforms that had hitherto been only superficially described. Outstanding aspects of Mackay's contributions are his genius for making critical field observations and his ability to use them to test geophysical theory. He was one of a very small number of pioneers who reconstructed periglacial geomorphology. Copyright © 2015 John Wiley & Sons, Ltd.

Early to mid Wisconsin Fluvial Deposits and Palaeoenvironment of the Kidluit Formation, Tuktoyaktuk Coastlands, Western Arctic Canada


The Kidluit Formation (Fm) is a fluvial sand deposit that extends regionally across the Tuktoyaktuk Coastlands, western Arctic Canada. It was deposited by a large river flowing north into the Arctic Ocean before development of a cold-climate sandy desert and later glaciation by the Laurentide Ice Sheet. Lithostratigraphic and sedimentological field observations of the Summer Island area indicate deposition of the Kidluit Fm by a braided river system. Optically stimulated luminescence (OSL) dating of Kidluit sand provides eight OSL ages of 76–27 ka, which indicate deposition during Marine Isotope Stage (MIS) 4 and MIS 3. Radiocarbon dating of well-preserved weevil remains, a willow twig, wild raspberry seeds and bulrush achenes provides non-finite 14C ages of >52 200, >51 700, >45 900 and >54 700 14C BP and are assigned an age of either MIS 4 or early MIS 3. Plant macrofossils from the sand deposit indicate spruce forest conditions and climate slightly warmer than present, whereas insect fossils indicate tundra conditions slightly colder than present. The river system that deposited the Kidluit Fm was probably either a pre-Laurentide Mackenzie River or the palaeo-Porcupine River, or a combination of the two. Copyright © 2017 John Wiley & Sons, Ltd.

A Model for Quantifying Ground-Ice Volume, Yukon Coast, Western Arctic Canada


A morphological model for estimating ground-ice contents of various landscape units is presented to address the gap between large-scale, general studies and small-scale, site-specific case histories. The model considers different ground-ice types and cryostratigraphic relations between ice bodies within a terrain unit. Input parameters needed for the model are described. Derived variables and algorithms used to determine the quantity of each ground-ice type within a terrain unit are presented. Examples of the application of the model are provided for the Yukon Coastal Plain, northwest Canada. The uncertainties and limiting assumptions of the model are discussed. Copyright © 2017 Natural Resources Canada. Permafrost and Periglacial Processes © 2017 John Wiley & Sons, Ltd.

Ground Temperatures and Permafrost Warming from Forest to Tundra, Tuktoyaktuk Coastlands and Anderson Plain, NWT, Canada


Annual mean ground temperatures (Tg) decline northward from approximately −3.0°C in the boreal forest to −7.0°C in dwarf-shrub tundra in the Tuktoyuktuk Coastlands and Anderson Plain, NWT, Canada. The latitudinal decrease in Tg from forest to tundra is accompanied by an increase in the range of values measured in the central, tall-shrub tundra zone. Field measurements from 124 sites across this ecotone indicate that in undisturbed terrain Tg may approach 0°C in the forest and −4°C in dwarf-shrub tundra. The greatest range of local variation in Tg (~7°C) was observed in the tall-shrub transition zone. Undisturbed terrain units with relatively high Tg include riparian areas and slopes with drifting snow, saturated soils in polygonal peatlands and areas near lakes. Across the region, the warmest permafrost is associated with disturbances such as thaw slumps, drained lakes, areas burned by wildfires, drilling-mud sumps and roadsides. Soil saturation following terrain subsidence may increase the latent heat content of the active layer, while increases in snow depth decrease the rate of ground heat loss in autumn and winter. Such disturbances increase freezeback duration and reduce the period of conductive ground cooling, resulting in higher Tg and, in some cases, permafrost thaw. The field measurements reported here confirm that minimum Tg values in the uppermost 10 m of permafrost have increased by ~2°C since the 1970s. The widespread occurrence of Tg above −3°C indicates warm permafrost exists in disturbed and undisturbed settings across the transition from forest to tundra. Copyright © 2017 Government of the Northwest Territories. Permafrost and Periglacial Processes © 2017 John Wiley & Sons, Ltd.

Can Deep Groundwater Influx be Detected from the Geochemistry of Thermokarst Lakes in Arctic Alaska?


In the continuous permafrost zone, unfrozen ground may exist beneath large lakes and streams. Sub-lake taliks that extend through permafrost provide a potential conduit for subpermafrost groundwater to reach the surface, increasing dissolved ion concentrations in lake water. Twenty-eight lakes on the Arctic Coastal Plain of northern Alaska were sampled in 2013–14 to determine whether a difference in ionic concentration could be detected between lakes with and without through taliks. A thermal model originally developed by J. Ross Mackay indicated that 20 of the lakes may have a talik that penetrates the permafrost. Lake water samples were analysed for a variety of ions and geochemical properties. Generally, there was little interannual variation in ion concentration, pH and specific conductivity of lake water. Proximal lakes tended to have similar chemical signatures, but there were large variations across the study region. Local factors appeared largely to control lake water chemistry. Lakes with suspected through taliks did not demonstrate a hydrochemical signature distinct from nearby lakes lacking a through talik. This suggests that either: (1) there is no hydrological connection with subpermafrost groundwater due to aquicludes in the subsurface; (2) the flux of groundwater is too small to have a measurable impact on lake water chemistry; or (3) the steady-state condition for talik configuration assumed in the thermal model is not justified. Copyright © 2016 John Wiley & Sons, Ltd.

Talik Formation at a Snow Fence in Continuous Permafrost, Western Arctic Canada


The long-term ground thermal effects of a snow fence were examined in continuous permafrost on Peel Plateau, Northwest Territories. As the fence was erected in the early 1980s, present-day ground thermal conditions include the response to over 30 years of snow pack modification. Snow cover, ground temperatures, late-summer thaw depth and moisture content are higher at the fence than in ground nearby. The terrain surface around the fence has subsided about 0.5 m due to the disturbance. Field measurements indicate that a talik has developed below the fence. Numerical simulation of the ground thermal regime beneath the snow drift suggests that the talik began to form 25 years after the fence was constructed, and that thaw depth in late summer is now about 3 m. Copyright © 2016 John Wiley & Sons, Ltd.

Thaw Subsidence in Undisturbed Tundra Landscapes, Barrow, Alaska, 1962–2015


In some regions underlain by ice-rich permafrost, a consistent, long-term increase in ALT under changing climatic conditions is not supported by observations. The apparent lack of ALT may be attributed to soil consolidation from thawing of the uppermost ice-rich permafrost and subsidence of the ground surface. Four plots established in 1962 at Barrow, Alaska, were re-instrumented in 2003 and surveyed annually using differential GPS technology, accompanied by active-layer probing. Elevation change from 1962 to 2003 was within the interannual variability of the 2003–15 period, indicating net stability in the area. Over the 2003–15 period, however, all four plots experienced subsidence trends of 0.4–1.0 cm/year, resulting in a net elevation change of 8–15 cm. Warmer winters and increased snow depth during this period decreased the potential for frost heave. Warmer summers resulted in thaw penetration into the ice-rich transient layer and ice wedges, leading to the net subsidence in recent years. Copyright © 2016 John Wiley & Sons, Ltd.

Lithalsa Formation and Holocene Lake-Level Recession, Great Slave Lowland, Northwest Territories


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.

Long-Term River Icing Dynamics in Discontinuous Permafrost, Subarctic Canadian Shield


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.