Massive Ground Ice Research Articles

Recent Advances (2008–2015) in the Study of Ground Ice and Cryostratigraphy

AbstractCryostratigraphy involves the description, interpretation and correlation of ground‐ice structures (cryostructures) and their relationship to the host deposits. Recent advances in the study of ground ice and cryostratigraphy concern permafrost aggradation and degradation, massive‐ice formation and evaluation of ground‐ice content. Field studies have increased our knowledge of cryostructures and massive ground ice in epigenetic and syngenetic permafrost. Epigenetic permafrost deposits are relatively ice‐poor and composed primarily of pore‐filled cryostructures, apart from an ice‐enriched upper section and intermediate layer. Syngenetic permafrost deposits are commonly identified from cryostructures indicative of an aggrading permafrost table and are characterised by a high ice content, ice‐rich cryofacies and nested wedge ice. Degradation of ice‐rich permafrost can be marked by thaw unconformities, truncated buried ice wedges, ice‐wedge pseudomorphs and organic‐rich ‘forest beds’. Studies of massive ground ice have focused on wedge ice, thermokarst‐cave ice, intrusive ice and buried ice. Significant advances have been made in methods for differentiating between tabular massive‐ice bodies of glacier and intrasedimental origin. Recent studies have utilised palynology, isotope geochemistry and hydrochemistry, in addition to sedimentary and cryostratigraphic analyses. The application of remote sensing techniques and laboratory methods such as computed tomography scanning has improved estimations of the ice content of frozen sediments. Copyright © 2016 John Wiley & Sons, Ltd.

InSAR Detection and Field Evidence for Thermokarst after a Tundra Wildfire, Using ALOS-PALSAR

Thermokarst is the process of ground subsidence caused by either the thawing of ice-rich permafrost or the melting of massive ground ice. The consequences of permafrost degradation associated with thermokarst for surface ecology, landscape evolution, and hydrological processes have been of great scientific interest and social concern. Part of a tundra patch affected by wildfire in northern Alaska (27.5 km2) was investigated here, using remote sensing and in situ surveys to quantify and understand permafrost thaw dynamics after surface disturbances. A two-pass differential InSAR technique using L-band ALOS-PALSAR has been shown capable of capturing thermokarst subsidence triggered by a tundra fire at a spatial resolution of tens of meters, with supporting evidence from field data and optical satellite images. We have introduced a calibration procedure, comparing burned and unburned areas for InSAR subsidence signals, to remove the noise due to seasonal surface movement. In the first year after the fire, an average subsidence rate of 6.2 cm/year (vertical) was measured. Subsidence in the burned area continued over the following two years, with decreased rates. The mean rate of subsidence observed in our interferograms (from 24 July 2008 to 14 September 2010) was 3.3 cm/year, a value comparable to that estimated from field surveys at two plots on average (2.2 cm/year) for the six years after the fire. These results suggest that this InSAR-measured ground subsidence is caused by the development of thermokarst, a thawing process supported by surface change observations from high-resolution optical images and in situ ground level surveys.

The evolution of a thermokarst-lake landscape: Late Quaternary permafrost degradation and stabilization in interior Alaska

Thermokarst processes characterize a variety of ice-rich permafrost terrains and often lead to lake formation. The long-term evolution of thermokarst landscapes and the stability and longevity of lakes depend upon climate, vegetation and ground conditions, including the volume of excess ground ice and its distribution. The current lake status of thermokarst-lake landscapes and their future trajectories under climate warming are better understood in the light of their long-term development. We studied the lake-rich southern marginal upland of the Yukon Flats (northern interior Alaska) using dated lake-sediment cores, observations of river-cut exposures, and remotely-sensed data. The region features thick (up to 40m) Quaternary deposits (mainly loess) that contain massive ground ice. Two of three studied lakes formed ~11,000–12,000calyr BP through inferred thermokarst processes, and fire may have played a role in initiating thermokarst development. From ~9000calyr BP, all lakes exhibited steady sedimentation, and pollen stratigraphies are consistent with regional patterns. The current lake expansion rates are low (0 to <7cmyr−1 shoreline retreat) compared with other regions (~30cmyr−1 or more). This thermokarst lake-rich region does not show evidence of extensive landscape lowering by lake drainage, nor of multiple lake generations within a basin. However, LiDAR images reveal linear “corrugations” (>5m amplitude), deep thermo-erosional gullies, and features resembling lake drainage channels, suggesting that highly dynamic surface processes have previously shaped the landscape. Evidently, widespread early Holocene permafrost degradation and thermokarst lake initiation were followed by lake longevity and landscape stabilization, the latter possibly related to establishment of dense forest cover. Partial or complete drainage of three lakes in 2013 reveals that there is some contemporary landscape dynamism. Holocene landscape evolution in the study area differs from that described from other thermokarst-affected regions; regional responses to future environmental change may be equally individualistic.

Methane in ground ice and frozen Quaternary deposits of Western Yamal

The content and the genesis of methane in underground ice and frozen Quaternary sediments of Western Yamal is studied. The minimum concentration of methane in frozen Quaternary deposits was found for sand: 15–100 ppm V. The maximum concentration of methane reaches 3000 ppm V in marine clays. The concentration of methane in the ice wedges is 100–700 ppm V, and in the massive ground ice can be more than 10 000 ppm V. The high content of methane in the massive ground ice we explain by migration of methane from freezing deposits into ice body during its formation. The close connection between methane concentration and organic carbon content is found.

Downstream patterns of suspended sediment transport in a High Arctic river influenced by permafrost disturbance and recent climate change

Spatially and temporally variable suspended sediment transport from upstream sources was investigated in the West River (unofficial name) at the Cape Bounty Arctic Watershed Observatory (CBAWO) on Melville Island, Nunavut (74°55′ N, 109°35′ W), a river with nearly a decade of hydrological and sediment transport research in the Canadian Arctic and subject to recent permafrost disturbances, such as soil skin flows on slopes, massive ground ice melt in the channel, and substantial climate change. During the 2012 season, a survey was undertaken during the nival period to identify areas of the river where the flow was isolated from the channel bed by snow and where it progressively reached the bed. During the nival period, and throughout the rest of the season, suspended sediment transport data were collected from a primary outlet station and six upstream locations to identify the sources and sinks of sediment in the various reaches of the West River. An inferred sediment budget approach was used to identify the storage and release dynamics in each reach. Nival event-scale hysteresis and seasonal diurnal hysteresis patterns for 2012 were primarily anticlockwise, suggesting that sources of sediment were not readily available for transport during peak flows but became available as discharge waned. Analysis of diurnal hysteresis relationships for the years 2004–2012 (excluding 2011) signals a shift in daily sediment-discharge hysteresis from primarily clockwise to anticlockwise following an episode of permafrost disturbance and enhanced erosion in 2007. Consistent sediment storage in the upper catchment from this disturbance is interpreted to have contributed to the shift to anticlockwise daily hysteresis. Results provide insights into the fluvial and geomorphological response to changes in sediment availability in Arctic rivers and how these changes in turn affect sediment transport in these environments.

Buried and Massive Ground Ice on the West Coast of Baidaratskaya Bay in the Kara Sea

Using data on the structure, conditions of occurrence (bedding), and the isotope composition of massive ice beds on the West coast of Baydaratskaya Bay it was established that the massive ice beds even occurring in the same outcrop may be related to different genetic types. There are two groups of the massive ice: 1) the «upper» thick (> 3 m) massive ice beds composed by buried basal glacier ice; and 2) the «lower» small ice beds (< 3 m), formed both intrasedimentally and as a result of burial of initially surface ice bodies. Sand thickness which included both groups of the massive ice started its formation before the glacial ice burial. As a result of advancing and later degradation of the glacier, probably moving from the Pay-Khoy ridge or from the Polar Ural, its lower (basal) parts were preserved within the permafrost thickness.

Dissolved organic carbon (DOC) in Arctic ground ice

Abstract. Thermal permafrost degradation and coastal erosion in the Arctic remobilize substantial amounts of organic carbon (OC) and nutrients which have accumulated in late Pleistocene and Holocene unconsolidated deposits. Permafrost vulnerability to thaw subsidence, collapsing coastlines and irreversible landscape change are largely due to the presence of large amounts of massive ground ice such as ice wedges. However, ground ice has not, until now, been considered to be a source of dissolved organic carbon (DOC), dissolved inorganic carbon (DIC) and other elements which are important for ecosystems and carbon cycling. Here we show, using biogeochemical data from a large number of different ice bodies throughout the Arctic, that ice wedges have the greatest potential for DOC storage, with a maximum of 28.6 mg L−1 (mean: 9.6 mg L−1). Variation in DOC concentration is positively correlated with and explained by the concentrations and relative amounts of typically terrestrial cations such as Mg2+ and K+. DOC sequestration into ground ice was more effective during the late Pleistocene than during the Holocene, which can be explained by rapid sediment and OC accumulation, the prevalence of more easily degradable vegetation and immediate incorporation into permafrost. We assume that pristine snowmelt is able to leach considerable amounts of well-preserved and highly bioavailable DOC as well as other elements from surface sediments, which are rapidly frozen and stored in ground ice, especially in ice wedges, even before further degradation. We found that ice wedges in the Yedoma region represent a significant DOC (45.2 Tg) and DIC (33.6 Tg) pool in permafrost areas and a freshwater reservoir of 4200 km2. This study underlines the need to discriminate between particulate OC and DOC to assess the availability and vulnerability of the permafrost carbon pool for ecosystems and climate feedback upon mobilization.

Ground ice as indicator of the Pleistocene history of the Russian Arctic

На основании анализа происхождения подземных залежных льдов рассмотрен вопрос о геологическом развитии Российской Арктики в четвертичный период. Предложена классификация пластовых льдов, содержащая два новых, выявленных автором генетических типа льдов - субмаринный и прибрежно-морской, для которых даётся новый механизм их образования. Установлена возможность формирования вечной мерзлоты с пластовыми льдами непосредственно в морских условиях. Выявлены существенные различия в геологическом развитии, в частности в трансгрессивно-регрессивном режиме, между западным и восточным секторами Арктики. Это ставит под сомнение ведущую роль гляциоэвстатических процессов в колебаниях уровня моря и выводит на первый план роль тектонических процессов.

Ground temperature variations in a talus slope influenced by permafrost: a comparison of field observations and model simulations

Abstract. Variations in surface and near-surface ground temperatures (GST) dominate the evolution of the ground thermal regime over time and represent the upper boundary condition for the subsurface. Focusing on the Lapires talus slope in the south-western part of the Swiss Alps, which partly contains massive ground ice, and using a joint observational and modelling approach, this study compares and combines observed and simulated GST in the proximity of a borehole. The aim was to determine the applicability of the physically based subsurface model COUP to accurately reproduce spatially heterogeneous GST data and to enhance its reliability for long-term simulations. The reconstruction of GST variations revealed very promising results, even though two-dimensional processes like the convection within the coarse-blocky sediments close to the surface or ascending air circulation throughout the landform ("chimney effect") are not included in the model. For most simulations, the model bias revealed a distinct seasonal pattern mainly related to the simulation of the snow cover. The study shows that, by means of a detailed comparison of GST simulations with ground truth data, the calibration of the upper boundary conditions – which are crucial for modelling the subsurface – could be enhanced.

FORMATION AND EVOLUTION OF THE RUSSIAN ARCTIC CRYOLITHOZONE (ON THE SHELF AND THE CONTINENT) IN THE PLEISTOCENE-HOLOCENE

The paper addresses age nonuniformity of the permafrost of the Russian Arctic shelf. It has been widely accepted that recent permafrost exists on the present-day shelf, which was formed under subaerial conditions during shelf draining in the Late Pleistocene, was flooded during the subsequent transgression, and now exists as a relic zone. However, there is also modern permafrost forming under submarine conditions. The paper considers the mechanism of its formation. The author suggests a mechanism that involves bottom soil freezing and ice formation due to constant natural transformations in seabed sediments. The proposed mechanism is supported by analyzes of certain sections of the bottom sediments of shelf and of the Pleistocene marine plains (ancient shelves) composed of dislocated sequences with massive ice beds. Analysis of the massive ground ice genesis identified different geological history as well as different transgressive and regressive regime of the Russian Arctic western and eastern sectors. The glacial cover has limited distribution in the Russian North and was absent on the Russian Arctic and Subarctic plains to the East of the Kanin Peninsula.

The coupled moisture‐heat process of permafrost around a thermokarst pond in Qinghai‐Tibet Plateau under global warming

AbstractDue to environmental disturbances such as local human activity and global warming, melting of massive ground ice has resulted in thermokarst ponds, which are extensively distributed in the Qinghai‐Tibet Plateau (QTP). Besides the global warming, the thermokarst pond, as a major heat source, speeds up the moisture change and degradation of its surrounding permafrost. To analyze the long‐term coupled moisture‐heat process near a representative nonpenetrative thermokarst pond in a permafrost region, abundant temperature data over multiple years at different depths and horizontal distances from the center of the thermokarst pond have been collected at a field experimental station in QTP. A numerical model is built to analyze this thermokarst pond. The temperature and moisture processes of surrounding permafrost are simulated by this model and compared with measured temperature data. Our results show that if the rate of air temperature rise is 0.048°C/yr, which refers to a 2.4°C temperature rise over 50 years, the thawing fronts underneath the thermokarst pond move downward at a linear rate of 0.18 m/yr and the permafrost beneath the pond center would disappear after the year of 2281. Beyond that time, the impact range of the pond on the natural ground increases to about 50 m in horizontal direction. So a dish‐shape thawing zone occurs around the thermokarst pond. Simultaneously, the moisture state is greatly changed in 2281 and becomes completely different from that in 2013. All of these would inevitably deteriorate the ecological and environmental system in QTP.

FORMATION AND EVOLUTION OF THE RUSSIAN ARCTIC CRYOLITHOZONE (ON THE SHELF AND THE CONTINENT) IN THE PLEISTOCENE-HOLOCENE

The paper addresses age nonuniformity of the permafrost of the Russian Arctic shelf. It has been widely accepted that recent permafrost exists on the present-day shelf, which was formed under subaerial conditions during shelf draining in the Late Pleistocene, was flooded during the subsequent transgression, and now exists as a relic zone. However, there is also modern permafrost forming under submarine conditions. The paper considers the mechanism of its formation. The author suggests a mechanism that involves bottom soil freezing and ice formation due to constant natural transformations in seabed sediments. The proposed mechanism is supported by analyzes of certain sections of the bottom sediments of shelf and of the Pleistocene marine plains (ancient shelves) composed of dislocated sequences with massive ice beds. Analysis of the massive ground ice genesis identified different geological history as well as different transgressive and regressive regime of the Russian Arctic western and eastern sectors. The glacial cover has limited distribution in the Russian North and was absent on the Russian Arctic and Subarctic plains to the East of the Kanin Peninsula.

A new data set for estimating organic carbon storage to 3 m depth in soils of the northern circumpolar permafrost region

Abstract. High-latitude terrestrial ecosystems are key components in the global carbon cycle. The Northern Circumpolar Soil Carbon Database (NCSCD) was developed to quantify stocks of soil organic carbon (SOC) in the northern circumpolar permafrost region (a total area of 18.7 × 106 km2). The NCSCD is a geographical information system (GIS) data set that has been constructed using harmonized regional soil classification maps together with pedon data from the northern permafrost region. Previously, the NCSCD has been used to calculate SOC storage to the reference depths 0–30 cm and 0–100 cm (based on 1778 pedons). It has been shown that soils of the northern circumpolar permafrost region also contain significant quantities of SOC in the 100–300 cm depth range, but there has been no circumpolar compilation of pedon data to quantify this deeper SOC pool and there are no spatially distributed estimates of SOC storage below 100 cm depth in this region. Here we describe the synthesis of an updated pedon data set for SOC storage (kg C m−2) in deep soils of the northern circumpolar permafrost regions, with separate data sets for the 100–200 cm (524 pedons) and 200–300 cm (356 pedons) depth ranges. These pedons have been grouped into the North American and Eurasian sectors and the mean SOC storage for different soil taxa (subdivided into Gelisols including the sub-orders Histels, Turbels, Orthels, permafrost-free Histosols, and permafrost-free mineral soil orders) has been added to the updated NCSCDv2. The updated version of the data set is freely available online in different file formats and spatial resolutions that enable spatially explicit applications in GIS mapping and terrestrial ecosystem models. While this newly compiled data set adds to our knowledge of SOC in the 100–300 cm depth range, it also reveals that large uncertainties remain. Identified data gaps include spatial coverage of deep (&gt; 100 cm) pedons in many regions as well as the spatial extent of areas with thin soils overlying bedrock and the quantity and distribution of massive ground ice. An open access data-portal for the pedon data set and the GIS-data sets is available online at http://bolin.su.se/data/ncscd/. The NCSCDv2 data set has a digital object identifier (doi:10.5879/ECDS/00000002).

The high elevation Dry Valleys in Antarctica as analog sites for subsurface ice on Mars

The high elevation valleys of the McMurdo Dry Valleys of Antarctica are the only locations on Earth known to contain dry permafrost. The Dry Valleys are a hyper-arid polar desert environment and above 1500m elevation, air temperatures do not exceed 0°C and thus, similarly to Mars, liquid water is largely absent and instead the hydrologic cycle is dominated by frozen ice and vapor phase processes such as sublimation. These conditions make the high elevation Dry Valleys a key Mars analog location where periglacial processes and geomorphic features, and their use as a diagnostic for subsurface ice, can be studied in situ. Two valleys in the upper Dry Valleys show a diversity of subsurface ice; University Valley is dominated by dry permafrost overlying ice-cemented to ice-bonded ground and nearby middle Beacon Valley is dominated by massive ground ice. In both cases the ice is 10–60cm below the surface. Here we compare the surface features in these two valleys to assess any correlation with the nature of the subsurface ice and compare these features to similar features seen at the Phoenix landing site on Mars. We conclude that while surface features may be indicative of ground ice, no specific correlations are possible and more direct methods are required to determine the nature of subsurface ice on Mars.

Thawing of massive ground ice in mega slumps drives increases in stream sediment and solute flux across a range of watershed scales

AbstractIce‐cored permafrost landscapes are highly sensitive to disturbance and have the potential to undergo dramatic geomorphic transformations in response to climate change. The acceleration of thermokarst activity in the lower Mackenzie and Peel River watersheds of northwestern Canada has led to the development of large permafrost thaw slumps and caused major impacts to fluvial systems. Individual “mega slumps” have thawed up to 106 m3of ice‐rich permafrost. The widespread development of these large thaw slumps (up to 40 ha area with headwalls of up to 25 m height) and associated debris flows drive distinct patterns of stream sediment and solute flux that are evident across a range of watershed scales. Suspended sediment and solute concentrations in impacted streams were several orders of magnitude greater than in unaffected streams. In summer, slump impacted streams displayed diurnal fluctuations in water levels and solute and sediment flux driven entirely by ground‐ice thaw. Turbidity in these streams varied diurnally by up to an order of magnitude and followed the patterns of net radiation and ground‐ice ablation in mega slumps. These diurnal patterns were discernible at the 103 km2 catchment scale, and regional disturbance inventories indicate that hundreds of watersheds are already influenced by slumping. The broad scale impacts of accelerated slumping are indicated by a significant increase in solute concentrations in the Peel River (70,000 km2). These observations illustrate the nature and magnitude of hydrogeomorphic changes that can be expected as glaciogenic landscapes underlain by massive ice adjust to a rapidly changing climate.

Periglacial landscape dynamics in the western Canadian Arctic: Results from a thermokarst lake record on a push moraine (Herschel Island, Yukon Territory)

Ice-rich permafrost landscapes are sensitive to climate and environmental change due to the melt-out of ground ice during thermokarst development. Thermokarst processes in the northern Yukon Territory are currently not well-documented. Lake sediments from Herschel Island (69°36′N; 139°04′W) in the western Canadian Arctic provide a record of thermokarst lake development since the early Holocene. A 727cm long lake sediment core was analyzed for radiographic images, magnetic susceptibility, granulometry, and biogeochemical parameters (organic carbon, nitrogen, and stable carbon isotopes). Based on eight calibrated AMS radiocarbon dates, the sediment record covers the last ~11,500years and was divided into four lithostratigraphic units (A to D) reflecting different thermokarst stages. Thermokarst initiation at the study area began ~11.5cal ka BP. From ~11.5 to 10.0cal ka BP, lake sediments of unit A started to accumulate in an initial lake basin created by melt-out of massive ground ice and thaw subsidence. Between 10.0 and 7.0cal ka BP (unit B) the lake basin expanded in size and depth, attributed to talik formation during the Holocene thermal maximum. Higher-than-modern summer air temperatures led to increased lake productivity and widespread terrain disturbances in the lake's catchment. Thermokarst lake development between 7.0 and 1.8cal ka BP (unit C) was characterized by a dynamic equilibrium, where lake basin and talik steadily expanded into ambient ice-rich terrain through shoreline erosion. Once lakes become deeper than the maximum winter lake ice thickness, thermokarst lake sediments show a great preservation potential. However, site-specific geomorphic factors such as episodic bank-shore erosion or sudden drainage through thermo-erosional valleys or coastal erosion breaching lake basins can disrupt continuous deposition. A hiatus in the record from 1.8 to 0.9cal ka BP in Lake Herschel likely resulted from lake drainage or allochthonous slumping due to collapsing shore lines before continuous sedimentation of unit D recommenced during the last 900years.

Application of electrical resistivity tomography in investigating depth of permafrost base and permafrost structure in Tibetan Plateau

Abstract The changes in the thickness of permafrost and the distribution characteristics of ground ice are of great importance for engineering and environmental issue research in permafrost regions. This study was conducted in the permafrost observation field in Qumahe in the east of the Tibetan Plateau by using electrical resistivity tomography (ERT) for investigating the depth of permafrost base and the structure of permafrost. The results demonstrated that the ERT can detect the depth of permafrost base, identify the characteristics of ground ice and the variation of permafrost types in Qumahe. Also, the effects and accuracy of ERT were evaluated combining the information provided by borehole and ground temperature monitoring. The comprehensive analysis of the data shows that the distribution of permafrost and ground ice in this area is strongly influenced by geographical, topographical and other local factors. The depth of the permafrost base within the observation field differs by 30 m. Aspect, surface water and vegetation conditions have the most significant influence on the thickness of permafrost. A seasonal stream in the low-lying area of the observation field also brings strong influence to permafrost thermal disturbance and thickness. Meanwhile, different geomorphic unit and surface conditions significantly influence the development of ground ice. To be specific, the massive ground ice is mainly developed in the flat swamping wetland, especially the low-lying wetland. In terms of depth, the massive ground ice is mainly developed within 5 to 10 m below the permafrost table.

Modeling challenges for predicting hydrologic response to degrading permafrost

The fate of the approximately 1,700 billion metric tons of carbon (Tarnocai et al. 2009) currently frozen in permafrost affected regions of the Arctic and subarctic is highly uncertain (IPCC 2007), primarily because of the potential for topographic evolution and resulting drainage network reorganization as permafrost degrades and massive ground ice contained in ice-rich permafrost soils melts. Computer modeling is a key tool in untangling these complex feedbacks to understand the evolution of the Arctic and subarctic landscapes and the potential feedbacks with the global climate system. Some of the challenges associated with modeling the hydrologic system in and around degrading permafrost are discussed in this essay. Modeling requirements depend very strongly on the spatial resolution of the model. Two different classes can be identified, depending on whether microtopography is explicitly resolved or incorporated into the model through a subgrid parameterization. The focus here is on the computational challenges associated with microtopography-resolving models using hydrologic response of polygon mires as an example. In such microtopography-resolving models, horizontal grid spacing on the order of 0.25mwould typically be required. Although highand low-centered ice wedge polygons have been identified as important controls on Arctic surface hydrology (e.g. Liljedahl et al. 2012) and evolution from lowto highcentered polygon landscapes is expected as Arctic temperatures increase (Jorgenson et al. 2006), as far as we are aware, there is no existing computer code that represents the full range of processes required to model the co-evolution of surface topography, active layer, and permafrost at the microtopography-resolving scale. For microtopography-resolving models of hydrology in permafrost landscapes, it is convenient to partition the large number of coupled processes into four critical sets: subsurface thermal/hydrology, surface thermal processes, mechanical deformation, and overland flow processes. However, it is important to recognize that the partitioning is somewhat arbitrary and that multiple tightly coupled processes exist within each set.

Ground ice in the upper permafrost of the Beaufort Sea coast of Alaska

Abstract Ground ice in the upper permafrost of the Beaufort Sea coast of Alaska was studied from 2005 to 2008 at 65 field sites located between Point Barrow and the Canadian border. The main terrain units in the studied area include (1) the primary surface of the coastal plain; (2) drained-lake basins; (3) low foothills (yedoma); (4) deltas and tidal flats; and (5) sand dunes. Wedge ice is the main type of massive ground ice, and ice-wedge polygons occurred on nearly all land surfaces. The volumetric content of wedge ice for the area varies from 3% to 50% between various terrain units with average value of about 11% for the entire coast. The highest content of wedge ice (about 50%) is typical of yedoma terrain, which occurred in a small segment at the coast of the Camden Bay. At the primary surface of the western region of the Arctic Coastal Plain, wedge-ice content reached almost 30%, with an average value of about 14%. Slightly smaller values were estimated for the primary surface of the eastern region of the Arctic Coastal Plain and for old drained-lake basins. Other types of massive ground ice included thermokarst-cave ice, ice cores of pingos, and a rare occurrence of folded massive ice at Barter Island. The content of segregated ice in organic and mineral soils between ice wedges was very high at most of the study sites. The total average volumetric ice content (due to wedge, segregated, and pore ice) for the whole area was 77%, ranging from 43% in eolian sand to 89% in yedoma.

Investigating internal structure of permafrost using conventional methods and ground-penetrating radar at Honhor basin, Mongolia

A ground-penetrating radar (GPR) survey was conducted at the end of August 2009 in the suburb region of Ulaanbaatar, Honhor basin, Mongolia, in combination with conventional methods such as borehole drilling and measurement of ground temperatures. The interface of frozen and unfrozen sediment was distinctly resolved in the interpreted GPR images, verified by the borehole drilling records and 6-month measurement of ground temperatures. The location of the permafrost table was assessed to be at the depth of 2–4 m in the study region. A conspicuous ice-saturated soil layer (massive ground ice) was detected in the interpreted GPR images with a thickness of 2–5 m. The GPR investigation results were consistent with the borehole drilling records and ground temperatures observation. The borehole logs and ground temperatures profile in the borehole indicates that permafrost at Honhor basin is characterized by high ground temperature and high ice content, which implies that ongoing climatic warming would have great influence on permafrost dynamics. The research results are of great importance to further assess permafrost dynamics to climatic change in the boundary of discontinuous and sporadic permafrost regions in Mongolia in the future.