Frost Mounds Research Articles

Perennial frost blisters of the outer Mackenzie Delta, western Arctic coast, Canada

ABSTRACTSaturated 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.

Internal Structure of a Lithalsa in the Akkol Valley, Russian Altai Mountains

Perennial frost mounds are present near the edges of ponds located on the terrace between the mountain flank and a valley-bottom lake in the Akkol valley of the Russian Altai Mountains. These mounds are 10–50 m in diameter and 3–6 m in height. We describe one mound, identified as a lithalsa, which had been eroded so as to expose almost its entire vertical cross-section, revealing its internal structure. The frozen core consisted mainly of soil segments suspended in reticulate ice lenses with a mean thickness of 11–48 mm and a maximum thickness of about 160 mm. The shapes of the soil segments matched their neighbours. Other features included soil segments suspended in the ice veins shaped like ‘En echelon gash veins’, and the presence of a radial structure of ice-rich and sediment-rich frozen bands. These features all suggest the greater importance of a differential stress field during heaving of the mound and after ice segregation, compared to the thermal gradient and water supply. Copyright © 2012 John Wiley & Sons, Ltd.

Thermal elasto-plastic computation model for a buried oil pipeline in frozen ground

The 813-mm-diameter China–Russia Crude Oil Pipeline enters northeastern China at Lianyin, Mo'he County, Heilongjiang Province and crosses 441 km of warm discontinuous, sporadic and isolated patches of permafrost and 512 km of seasonally frozen ground before reaching Daqing, China. It is inevitable that the buried pipeline is subject to frost heave and/or thaw settlement when it passes through regions of permafrost and seasonally frozen ground with available moisture. Therefore, stress and deformation analyses of the pipe subject to frost action or thaw settlement are important for the safety, long-term stability and economic feasibility of the buried oil pipeline system. Based on the (empirical) frost heave and/or thaw settlement coefficients, a simple thermal elasto-plastic finite element computation model is put forward for analyzing the stress and strain state of the pipe. The influences of soil temperatures on the soil deformation were considered, but those of the soil deformation on the soil temperatures were ignored in the modelling. Finally, two examples of the application of the computation model are presented, in which the stress and deformation of a pipe exposed to frost heave or thaw settlement is calculated. The results of the frost action computation show that the effective stress on the pipe increases linearly with the frost heave deformation. The largest pipe deformations and stresses may occur when crossing frost mounds due to differential frost heaving. The stress and deformation smooth out from the frost mound. The results of thaw settlement computation show that the pipe stress changes greatly near the interface of thaw settlement zone and no thaw settlement zone, and the thaw settlement has small effect on the stability of oil-pipeline. The computation results show that the oil pipeline design in the permafrost regions should pay more attention on frost heave hazard than thaw settlement hazard.

Icing processes associated with high Arctic perennial springs, Axel Heiberg Island, Nunavut, Canada

AbstractSaline perennial springs have been documented at six locations on Axel Heiberg Island in the Canadian high Arctic. Spring discharge rates, temperatures and chemistry, and associated icing and frost mound formation have been documented at two locations in the Expedition Fiord area since 1988 and at one location near Whitsunday Bay since 1996. Cold Ca‐ and Na‐rich waters discharge near the base of Gypsum Hill and Colour Peak at Expedition Fiord. A large oval‐shaped icing up to 2 m thick forms at the base of Gypsum Hill while at Colour Peak the springs have formed a series of gullies and travertine deposits which develop three small icing and frost mounds systems in winter. At Whitsunday Bay cold discharge is from a single outlet and is confined by a deep channel where it forms a salt tufa. Where the channel emerges onto the floodplain a large fan‐shaped icing is formed. This paper also documents spring discharge and icing activity from three other non‐glacial sources and one glacial source. The icings and frost mounds formed by these springs are very different from those formed by late summer and early winter subglacial discharge. The high solute concentrations lead to freezing‐point depression, complex patterns of freezing and the formation of brine icings, together with a variety of mineral precipitates. Freezing‐point depression experiments help explain icing hydrology and the spatial pattern of icing formation. Copyright © 2005 John Wiley & Sons, Ltd.

Present-Day Periglacial Environments in Central Spitsbergen, Svalbard

This report overviews observations on periglacial geomorphology in central Spitsbergen, which have been undertaken by the Japanese geomorphological groups. Focus is given to permafrost-related processes, including solifluction, thermal contraction cracking and pingo growth. Annual freeze-thaw action dominates the ground, resulting in extensive occurrence of solifluction and shallow landslides on soil slopes. Solifluction shows low surface velocity but large volumetric transport, which respectively reflects infrequent diurnal frost creep and deep movement. The latter partly originates from plug-like flow in the basal active layer, where permafrost temperature is low and muddy sediment is thick. Non-sorted polygons with a wide range of diameters develop on lowlands. In colder inland terrains, large polygons (>7m) have ice wedges, whereas smaller polygons have only soil wedges or cracks confined to the active layer. Significant ice-wedge cracking occurs during rapid and intensive cooling in midwinter. In warmer coastal terrains, ice wedges are not common even below large polygons, because higher winter temperature can produce only shallow cracks. Open-system pingos occur in valley bottoms and near shores. Some pingos are still growing under a low artesian pressure fed by constant supply of sub-permafrost water. Following lateral river erosion, a new frost mound emerged at a side of a pingo, reaching 3m high during three years. The observations demonstrate that central Spitsbergen is situated in a High Arctic but relatively warm permafrost environment. The transitional condition between cold and warm permafrost allows diverse periglacial features to coexist within a small area. Even minor climatic change can switch the two thermal regimes, affecting significantly the type and magnitude of periglacial processes.

Pingo Growth and collapse, Tuktoyaktuk Peninsula Area, Western Arctic Coast, Canada: a long-term field study

Growth data from precise surveys have been obtained for 11 pingos for periods ranging from 20 to 26 years. Most of the 1350 pingos, perhaps one quarter of the world's total, have grown up in the bottoms of drained lakes underlain by sands. Permafrost aggradation on the drained lake bottoms has resulted in pore water expulsion, solute rejection below the freezing front, a freezing point depression, and groundwater flow at below 0° C to one or more residual ponds, the sites of pingo growth. Sub-pingo water lenses underlie many growing pingos.The pure ice which grows by downward freezing in a sub-pingo water lens may be composed of seasonal growth bands which, like tree rings, are of potential use in the study of past climates. Growing pingos underlain by sub-pingo water lenses can often be identified by features such as peripheral pingo rupture, spring flow, frost mound growth, normal faulting, and oscillations in pingo height. Such features, and others, are associated with hydrofracturing and water loss from a sub-pingo water lens. Some of the data derived from the long-term study of pingo growth are relevant to the identification of collapse features, interpreted as paleo pingos, in areas now without permafrost.

Boreal peatland C fluxes under varying permafrost regimes

Discontinuous permafrost in peatlands has recently been melting across western Canada, creating wet Sphagnum-Carex lawns (internal lawns) interspersed within drier ombrotrophic bog. Permafrost degradation alters peat hydrology, thermal regimes and plant species assemblages, all of which could affect gaseous C emissions in peatlands. We quantified CO 2 and CH 4 fluxes across the peat-atmosphere boundary using dark static chambers in adjacent internal lawns, continental bogs and frost mounds in an area of localized permafrost in north-central Saskatchewan. Carbon dioxide and CH 4 fluxes ranged from 0.2 to 14.6 mmol CO 2 m −2 d −1 and from −24 to 344 μmol CH 4, respectively, and differed significantly among peatland types and sampling dates. Our estimates of CH 4 flux are low compared to previous estimates from boreal wetlands, with net consumption of CH 4 typically in frost mounds. Permafrost melt in our study area is associated with 1.6- and 30-fold increases in CO 2 and CH 4 emissions, respectively. More widespread thaw across the discontinuous permafrost region will be an important consideration to boreal C budgets with future climatic changes.

Plant community and diversity change due to localized permafrost dynamics in bogs of western Canada

Localized permafrost formation and melt at the southern limit of permafrost has a large effect on boreal bog plant community structure and diversity in continental western Canada (Alberta, Saskatchewan, and Manitoba). Non-metric multidimensional scaling ordinations show that non-permafrost-affected bogs, areas currently underlain by permafrost (frost mounds), and areas of permafrost degradation (internal lawns) have distinct plant communities. Bryophytes respond more strongly than vascular plants to lengthened environmental gradients in the bogs studied. Seventy-two vascular plant and bryophyte species were found, with mean alpha diversity (species richness) similar in bogs and internal lawns (22.6 and 22.1) and lowest on frost mounds (15.6). Beta diversity (species turnover between landforms) is greater for bryophytes (4.22) than vascular plants (2.54). Comparisons within internal lawns show highly variable height above water table, community composition, and species diversity in wet communities and reduced variability as peat accumulates and converges on dry surfaces dominated by Sphagnum fuscum (Schimp.) Klinggr. Overall, localized permafrost dynamics increase bog plant diversity by 47% by introduction of unique dry, shaded (frost mound) and wet, open (internal lawn) conditions absent from non-permafrost-affected bogs, making localized permafrost bogs one of the most bryologically diverse peatland types in western Canada.Key words: peatlands, bryophytes, plant communities, non-metric multidimensional scaling ordination, permafrost, climate change.

Localized Permafrost Peatlands in Western Canada: Definition, Distributions, and Degradation

Detailed inventory of peatlands by aerial photography shows that peatlands with climatically sensitive localized islands of permafrost cover 17,505 km2 within a broad band of occurrence in continental western Canada (Alberta, Saskatchewan, and Manitoba). Within this zone, 37.5% of the total area covered by bog, and 9.1% of total area covered by fen have localized permafrost landforms (frost mounds and/or internal lawns). Regional distribution of the presence/absence of localized permafrost peatlands relative to expansive peat plateaus (peatland completely underlain by permafrost) shows that a north to south landform gradient exists that is dominantly controlled by mean annual temperature. Percent cover of localized permafrost peatland in an area is best explained by the amount of total peatland cover that can support it. Localized permafrost is associated with collapse forms (internal lawns) throughout the range of its occurrence in western Canada. In some locations permafrost has completely melted, moving the current southern limit of permafrost north by 39 km on average, and by as much as 200 km.

Localized Permafrost Peatlands in Western Canada: Definition, Distributions, and Degradation

Detailed inventory of peatlands by aerial photography shows that peatlands with climatically sensitive localized islands of permafrost cover 17,505 km2 within a broad band of occurrence in continental western Canada (Alberta, Saskatchewan, and Manitoba). Within this zone, 37.5% of the total area covered by bog, and 9.1% of total area covered by fen have localized permafrost landforms (frost mounds and/or internal lawns). Regional distribution of the presence/absence of localized permafrost peatlands relative to expansive peat plateaus (peatland completely underlain by permafrost) shows that a north to south landform gradient exists that is dominantly controlled by mean annual temperature. Percent cover of localized permafrost peatland in an area is best explained by the amount of total peatland cover that can support it. Localized permafrost is associated with collapse forms (internal lawns) throughout the range of its occurrence in western Canada. In some locations permafrost has completely melted, moving the current southern limit of permafrost north by 39 km on average, and by as much as 200 km.

Thermokarst sediments and sedimentary structures, Tuktoyaktuk Coastlands, western Arctic Canada

Abrupt climate warming during glacial–interglacial transitions promotes regional thermokarst activity in areas of ice-rich permafrost. The ensuing thaw-related processes of melt-out, soft-sediment deformation and resedimentation may produce widespread thermokarst sediments and sedimentary structures. Examples of the most distinctive thermokarst sediments and sedimentary structures from the Tuktoyaktuk Coastlands, western Arctic Canada, comprise: (1) soft-sediment deformation structures (thermokarst involutions) in a palaeoactive layer; (2) ice-wedge casts and composite-wedge casts; (3) peaty to sandy diamicton deposited mainly by debris flows in retrogressive thaw slumps; and (4) a basal unit of diamicton and/or impure sand in some thermokarst-basin sequences, deposited by progradation of resedimented materials in thermokarst lakes. Many of the thermokarst sediments and sedimentary structures in the Tuktoyaktuk Coastlands formed as a result of rapid climate warming during the last glacial–interglacial transition, although some continue to form at present due to local (non-climatic) factors. Identification of thermokarst sediments and sedimentary structures in the geological record requires evidence for the thaw of excess ice. Direct evidence for the former occurrence of excess ice includes: (1) ice-wedge casts; (2) composite-wedge casts; (3) lenticular platy microstructures in frost-susceptible sediment; (4) certain near-surface brecciation of frost-susceptible bedrock; and (5) ramparted depressions attributed to the decay of frost mounds. Indirect evidence for former excess ice results where thaw consolidation initiates soft-sediment deformation or gelifluction.

Preferential groundwater flow through a sorted net landscape, Arctic Canada

Preferential suprapermafrost groundwater flow was observed in deepened channels lying between raised frost mounds. Here, saturated hydraulic conductivity, k, ranged from 90 to 1000 m/day but was only 0·1–1·0 m/day in the mound centres. A high proportion of fines occurs in the frost mound centre due to particle sorting, while channels contain gravels. Three approaches of areal weighting of k and groundwater flow, Q s, across a wetland–upland boundary were explored. When percentage area covered by channels, mounds or gravel was considered, estimates of water flow on a daily and seasonal basis fell by 30 to 50 per cent. This study is of relevance to northern scientists who require reliable estimates of groundwater flow across patterned ground landscapes. Copyright © 2001 John Wiley & Sons, Ltd.

Frozen ground phenomena in the vicinity of terra nova bay, northern victoria land, antarctica: a preliminary report

Frozen ground phenomena in the Northern Foothills, Northern Victoria Land, Antarctica, include large–scale polygons, 15–20 m in diameter, and small frost mounds, 1–5 m high. The polygons are most widespread on terrain formed upon Younger Drift and are usually surrounded by interpolygon furrows or troughs, 10–30 cm deep and 10–100 cm wide. The troughs contain shallow wedges of sandy gravel (sand wedges) near the surface but excavations into underlying permafrost indicate that small ice wedges or ice veins are locally present. Field and anecdotal evidence suggest that thermal contraction cracking is active under today's climate. Frost mounds occur in association with a number of perennially frozen lakes in the region. In most cases they appear related to frost and icing blister activity caused by the episodic injection of free water from below. The debris–covered nature of the centre of Enigma Lake is best explained in terms of basal ice accretion beneath the lake–ice cover.

Recent Permafrost Dynamics in a Subarctic Floodplain Associated with Changing Water Levels, Québec, Canada

We have reconstructed from tree-rings the dynamics of mineral frost mounds on the floodplain of a subarctic river (Rivière Boniface, northern Québec) likely associated with snow precipitation and temperature changes during the past centuries. Due to their peculiar location in the river bed, we have postulated that the inception and decay of frost mounds (thermokarst ponds) were associated with snow-controlled water levels of the river. The periods of establishment, growth, and mortality of spruce around and in two thermokarst ponds on the shore zone were identified. The oldest tree-ring dates show that permafrost mounds formed during a period of water lowering in the 17th century, likely in a long-enduring sequence of low waters initiated around cal AD 1150 (910 yr BP), which persisted for at least 200 yr until the beginning of the 20th century. Two main periods of spruce mortality were identified, in the late 19th century and early 20th century and in the 1950s–1960s, which corresponded to a rising river level probably due to greater snow precipitation. The patterns of spruce establishment and mortality were strikingly similar in the studied sites. The first spruce to establish were all located along the pond's edges and they were also the first ones to die; most of the youngest spruce established later in the central part of each feature, i.e., in the early to mid-1850s to 1910, and died during the 1950s–1960s. The sequence of events reported here suggests an important lowering of the Rivière Boniface during the first part of the Little Ice Age (end of the 16th century–17th century) which was drier and cold. During the second part of the Little Ice Age (mainly 19th century), greater precipitation occurred and climaxed in the 20th century when climate warmed and the river stage reached its maximum level. Changes in snow precipitation were probably more instrumental than temperature changes in the rise and fall of permafrost landforms because of the snowpack's direct influence on the soil thermal regime and river level during snowmelt.

Recent Permafrost Dynamics in a Subarctic Floodplain Associated with Changing Water Levels, Quebec, Canada

We have reconstructed from tree-rings the dynamics of mineral frost mounds on the floodplain of a subarctic river (Riviere Boniface, northern Quebec) likely associated with snow precipitation and temperature changes during the past centuries. Due to their peculiar location in the river bed, we have postulated that the inception and decay of frost mounds (thermokarst ponds) were associated with snow-controlled water levels of the river. The periods of establishment, growth, and mortality of spruce around and in two thermokarst ponds on the shore zone were identified. The oldest tree-ring dates show that permafrost mounds formed during a period of water lowering in the 17th century, likely in a long-enduring sequence of low waters initiated around cal AD 1150 (910 yr BP), which persisted for at least 200 yr until the beginning of the 20th century. Two main periods of spruce mortality were identified, in the late 19th century and early 20th century and in the 1950s-1960s, which corresponded to a rising river level probably due to greater snow precipitation. The patterns of spruce establishment and mortality were strikingly similar in the studied sites. The first spruce to establish were all located along the pond's edges and they were also the first ones to die; most of the youngest spruce established later in the central part of each feature, i.e., in the early to mid-1850s to 1910, and died during the 1950s-1960s. The sequence of events reported here suggests an important lowering of the Riviere Boniface during the first part of the Little Ice Age (end of the 16th century-17th century) which was drier and cold. During the second part of the Little Ice Age (mainly 19th century), greater precipitation occurred and climaxed in the 20th century when climate warmed and the river stage reached its maximum level. Changes in snow precipitation were probably more instrumental than temperature changes in the rise and fall of permafrost landforms because of the snowpack's direct influence on the soil thermal regime and river level during snowmelt.

Possible Frost Mounds in an Ancient Martian Lake Bed

Circular to elongated mounds are observed in Gusev crater in the Aeolis subquadrangle of Mars. They are arranged in a large cluster and show different stages of evolution, from fresh to scar structures. Their morphology and morphometric ratios are comparable to those of terrestrial frost mounds. This study shows how the paleolacustrine environment of the Ma'adim Vallis/Gusev crater hydrogeologic system may have provided a suitable environment for the formation of frost mounds. Alternate hypotheses of formation including volcanism, fluvial erosion, and eolian erosion are discussed. Other features such as heavings, curvilinear troughs, hills, ridges, and depressions support the idea of a sediment/ice interaction. The typology of the mounds and plausible mechanisms for their formation are proposed. Their presence could support the model of a massive water body in Gusev during the Amazonian and provide indicators of paleoenvironmental conditions at the time of their formation.

Perennial spring occurrence in the Expedition Fiord area of western Axel Heiberg Island, Canadian High Arctic

This paper documents perennial spring activity at Expedition Fiord on western Axel Heiberg Island in the Canadian High Arctic. Two groups of mineralized springs occur near the McGill University Axel Heiberg Research Station located at 79°26'N, 90°46'W. The first is at Gypsum Hill, 3 km from the terminus of the White and Thompson glaciers, and the second site is at Colour Peak, approximately 10 km downvalley near the head of Expedition Fiord. Each spring group consists of 20-40 vents spread over several hundred square metres. The highly mineralized nature of the discharge causes a freezing-point depression of 7-10°C and produces a range of precipitates and travertine deposits. Year-round water temperature and discharge rate measurements have been obtained, demonstrating perennial activity at these sites. Results indicate that temperatures range from -4.0 to 6.6°C among the individual sources; however, water temperatures at the various outlets remain constant throughout the year despite a mean annual air temperature of -15°C. Although discharge from any one outlet is low (<0.5 to 2.0 L/s), the total discharge is substantial, each year producing several seasonal frost mounds and an icing 180 000 - 300 000 m2 at the Gypsum Hill site.

Perennial spring occurrence in the Expedition Fiord area of western Axel Heiberg Island, Canadian High Arctic

This paper documents perennial spring activity at Expedition Fiord on western Axel Heiberg Island in the Canadian High Arctic. Two groups of mineralized springs occur near the McGill University Axel Heiberg Research Station located at 79°26'N, 90°46'W. The first is at Gypsum Hill, 3 km from the terminus of the White and Thompson glaciers, and the second site is at Colour Peak, approximately 10 km downvalley near the head of Expedition Fiord. Each spring group consists of 20-40 vents spread over several hundred square metres. The highly mineralized nature of the discharge causes a freezing-point depression of 7-10°C and produces a range of precipitates and travertine deposits. Year-round water temperature and discharge rate measurements have been obtained, demonstrating perennial activity at these sites. Results indicate that temperatures range from -4.0 to 6.6°C among the individual sources; however, water temperatures at the various outlets remain constant throughout the year despite a mean annual air temperature of -15°C. Although discharge from any one outlet is low (<0.5 to 2.0 L/s), the total discharge is substantial, each year producing several seasonal frost mounds and an icing 180 000 - 300 000 m2 at the Gypsum Hill site.

Formation of injection frost mounds over winter 1995–1996 at barrow, Alaska1

A group of ice‐cored frost mounds formed during the winter of 1995–1996 near Barrow, Alaska in a drained thaw‐lake basin. Over 20 mounds, ranging from 5 to 20 m across, were observed in mid‐August ...

Landforms and ground ice as evidence of the source of H2O in permafrost

Selected landforms and the ice in permafrost may be used as indicators of the direction of moisture input into perennially frozen ground. Accumulation of ice from meteoric sources from above may be the most widespread process, being dominant in the palsas, peat plateaus, and near-slope rock glaciers studied so far. It is also the main source of ice accumulation in permafrost. Pingos and seasonal frost mounds are the result of injection of ground water from below. The resulting ice content usually exceeds 90% by volume and some massive icy beds in Arctic Canada may also form in this way. Glacial ice is also proven as a source for some massive icy beds and may represent an Arctic form of ice stagnation. Segregation of ice by water moving to the freezing plane is very important in active layer processes and the initial formation of peat plateaus and palsas, but is probably of secondary importance thereafter. More work is needed to confirm these relationships and to prove the origin of near-glacier rock glaciers. However, if these relationships prove reliable, then the landforms can be used as indicators of potential sources of ice so that foundation designs can be modified to minimize heaving problems.