Genetic Identification Of Ground Ice By Petrographic Method

The advantages and limitations of the petrography method and the relevance of its use for the study of natural ice are reviewed in the present work. The petrographic method of ground ice study is often used for solving paleogeographic issues. The petrofabric analysis of ground ice is not only useful for descriptive purposes but, like the study of cryostructures, helps to infer growth processes and conditions. Different types of natural ice have specific features that can help us to determine ice genesis. Surface ice, such as glacier ice is often presented by foliation formed by large crystals (50-60 mm); lake ice is characterised by the upper zone of small (6 mm x 3 mm) dendritic and equigranular crystals, which change with increasing depth to large (may exceed 200 mm) columnar and prismatic crystals; segregated ice is composed by crystals forming foliation. Ground ice, such as ice wedge is presented by vertical-band appearance and small crystals (2-2.5 mm); closed-cavity ice is often distinguished by radial-ray appearance produced by elongated ice crystals; injection ice is composed by anhedral crystals, showing the movement of water; snowbank ice is presented by a high concentration of circular bubbles and small (0.1-1 mm) equigranular crystals; icing is described by foliation and mostly columnar crystals. Identification of the origin of ground ice is a complicated task for geocryology because it is difficult to distinguish different types of ground ice based on only visual explorations. The simplest way to get an ice texture pattern is by using polarized light. Distinctions between genetic types of ground ice are not always made in studies, and that can produce erroneous inferences. Petrography studies of an ice object are helpful to clarify the data interpretation, e.g., of isotopic analyses. It is particularly relevant for heterogeneous ice wedges’ study.

Contribution of ground ice melting to the expansion of Serling Co lake on the Tibetan Plateau

Serling Co lake, surrounded by permafrost and glacier-occupied regions, has exhibited the greatest increase in water storage over the last 50 years among all the lakes on the Tibetan Plateau. However, increases in precipitation and glacial melting are not enough to explain the increased water volume of lake expansion. The magnitude of the contribution of thawing permafrost to this increase under climate warming remains unknown. This study made the first attempt to quantify the water contribution of ground ice melting to the expansion of Serling Co lake by evaluating the ground surface deformation. We monitored the spatial distribution of surface deformation in the Serling Co basin using the SBAS-InSAR technique and compared it with the findings of field surveys. Then, the ground ice meltwater volume in the watershed was calculated based on the long-term deformation rate. Finally, this volume was compared with the lake volume change during the same period, and the contribution ratio was derived. SBAS-InSAR monitoring during 2017–2020 illustrated widespread and large subsidence in the upstream section of the Zhajiazangbu subbasin, where widespread continuous permafrost is present. The terrain subsidence was normally between 5 and 20 mm/a, indicating rapid ground ice loss in the region. The ground ice meltwater reached 56.0 × 106 m3/a, and the rate of increase in lake water storage was 496.3 × 106 m3/a during the same period, with ground ice meltwater contributing 11.3 % of the lake volume increase. This study is especially helpful in explaining the rapid expansion of Serling Co lake and equilibrating the water balance at the watershed scale. More importantly, the proposed method can be easily extended to other watersheds underlain by permafrost and to help understand the hydrologic changes in these watersheds.

The Ice-Rich Permafrost Sequences as a Paleoenvironmental Archive for the Kara Sea Region (Western Arctic)

The Kara Sea coast and part of the shelf are characterized by wide presence of the ice-rich permafrost sequences containing massive tabular ground ice (MTGI) and ice wedges (IW). The investigations of distribution, morphology and isotopic composition of MTGI and IW allows paleoenvironmental reconstructions for Late Pleistocene and Holocene period in the Kara Sea Region. This work summarizes result of long-term research of ice-rich permafrost at eight key sites located in the Yamal, Gydan, Taimyr Peninsulas, and Sibiryakov Island. We identified several types of ground ice in the coastal sediments and summarized data on their isotopic and geochemical composition, and methane content. We summarized the available data on particle size distribution, ice chemical composition, including organic carbon content, and age of the enclosing ice sediments. The results show that Quaternary sediments of the region accumulated during MIS 5 – MIS 1 and generally consisted of two main stratigraphic parts. Ice-rich polygenetic continental sediments with syngenetic and epigenetic IW represent the upper part of geological sections (10–15 m). The IW formed in two stages: in the Late Pleistocene (MIS 3 – MIS 2) and in the Holocene cold periods. Oxygen isotope composition of IW formed during MIS 3 – MIS 2 is on average 6‰ lower than that of the Holocene IW. The saline clay with rare sand layers of the lower part of geological sections, formed in marine and shallow shelf anaerobic conditions. MTGI present in the lower part of the sections. The MTGI formed under epigenetic freezing of marine sediments immediately after sea regression and syngenetic freezing of marine sediments in the tidal zone and in the conditions of shallow sea.

Soil water sources in permafrost active layer of Three-River Headwater Region, China

Water in permafrost soil is an important factor affecting the ecology of cold environments, climate change, hydrological cycle, engineering, and construction. To explore the variations in soil water in the active layer due to permafrost degradation, the soil water sources in the Three-River Headwater Region were quantified based on the stable isotope data (δ2H and δ18O) of 1140 samples. The results showed that the evaporation equation was δ2H = 7.46 δ18O - 0.37 for entire soil water. The stable isotope data exhibited a spatial pattern, which varied over the soil profile under the influence of altitude, soil moisture, soil temperature, vegetation, precipitation infiltration, soil water movement, ground ice, and evaporation. Based on the stable isotope tracer model, precipitation and ground ice accounted for approximately 88 % and 12 % of soil water, respectively. High precipitation contributed to the soil water in the 3900–4100 m, 4300–4500 m, and 4700–4900 m zones, whereas ground ice contributed to the soil water in the 4500–4700 m and 4900–5100 m zones. Precipitation contributed approximately 84 % and 80 % to the soil water in grasslands and meadows, respectively, whereas ground ice contributed approximately 16 % and 20 %, respectively. Precipitation; evapotranspiration; physical and chemical properties of soil; and the distribution of ground ice, vegetation, and permafrost degradation were the major factors affecting the soil water sources in the active layer. Therefore, establishing an observation network and developing technologies for ecosystem restoration and conservation is critical to effectively mitigate ecological problems caused by future permafrost degradation in the study region.

Formation of Gas-Emission Craters in Northern West Siberia: Shallow Controls

Gas-emission craters discovered in northern West Siberia may arise under a specific combination of shallow and deep-seated permafrost conditions. A formation model for such craters is suggested based on cryological and geological data from the Yamal Peninsula, where shallow permafrost encloses thick ground ice and lenses of intra- and subpermafrost saline cold water (cryopegs). Additionally, the permafrost in the area is highly saturated with gas and stores large accumulations of hydrocarbons that release gas-water fluids rising to the surface through faulted and fractured crusts. Gas emission craters in the Arctic can form in the presence of gas-filled cavities in ground ice caused by climate warming, rich sources of gas that can migrate and accumulate under pressure in the cavities, intrapermafrost gas-water fluids that circulate more rapidly in degrading permafrost, or weak permafrost caps over gas pools.

Catastrophic gas blowout in 2020 on the Yamal Peninsula in the Arctic. Results of comprehensive analysis of aerospace RS data

The researchers carried out comprehensive study of the Bovanenkovo C17 object of a catastrophic gas blowout in 2020 based on RS data from space and using UAV. For the first time, based on the UAV data, they created a digital 3D model of a cavity in a ground ice massif, in which gas-dynamic processes developed. The dimensions of the cavity bottom are 14×61.5 m, and its height before the explosion was 25-30 m. The 3D model allows research in virtual space. According to RS data from space, the researchers have proved more than half a century of slow growth of the perennial heaving mound (PHM) C17 and established that its explosion occurred from May 28 to June 9. Based on the analysis of digital elevation models (DEM) ArcticDEM in the period of 2011-2017 they revealed an uneven growth rate of the PHM surface — on average 8 cm/year, maximum up to 20 cm/year. The scientists confirmed the formation features of gas-saturated cavities in the massifs of ground ice under the influence of endogenous processes, gas-dynamic growth of PHMs, powerful blowouts, self-ignitions and explosions of gas with the formation of giant craters. The results make it possible to reduce the risks of emergencies and catastrophic situations at the facilities of the oil and gas industry in the Arctic.

Towards accurate quantification of ice content in permafrost of the Central Andes – Part II: an upscaling strategy of geophysical measurements to the catchment scale at two study sites

With ongoing climate change, there is a pressing need to better understand how much water is stored as ground ice in areas with extensive permafrost occurrence and how the regional water balance may alter in response to the potential generation of melt water from permafrost degradation. However, field-based data on permafrost in remote and mountainous areas such as the South-American Andes is scarce and most current ground ice estimates are based on broadly generalised assumptions such as volume-area scaling and mean ground ice content estimates of rock glaciers. In addition, ground ice contents in permafrost areas outside of rock glaciers are usually not considered, resulting in a significant uncertainty regarding the volume of ground ice in the Andes, and its hydrological role. In part I of this contribution, Hilbich et al. (submitted) present an extensive geophysical data set based on Electrical Resistivity Tomography (ERT) and Refraction Seismic Tomography (RST) surveys to detect and quantify ground ice of different landforms and surface types in several study regions in the semi-arid Andes of Chile and Argentina with the aim to contribute to the reduction of this data scarcity. In part II we focus on the development of a methodology for the upscaling of geophysical-based ground ice quantification to an entire catchment to estimate the total ground ice volume (and its estimated water equivalent) in the study areas. In addition to the geophysical data, the upscaling approach is based on a permafrost distribution model and classifications of surface and landform types. Where available, ERT and RST measurements were quantitatively combined to estimate the volumetric ground ice content using petrophysical relationships within the Four Phase Model (Hauck et al., 2011). In addition to introducing our upscaling methodology, we demonstrate that the estimation of large-scale ground ice volumes can be improved by including (i) non-rock glacier permafrost occurrences, and (ii) field evidence through a large number of geophysical surveys and ground truthing information. The results of our study indicate, that (i) conventional ground ice estimates for rock-glacier dominated catchments without in-situ data may significantly overestimate ground ice contents, and (ii) substantial volumes of ground ice may also be present in catchments where rock glaciers are lacking.

Geomorphology and InSAR-Tracked Surface Displacements in an Ice-Rich Yedoma Landscape

Ice-ridge Yedoma terrain is susceptible to vertical surface displacements by thaw and refreeze of ground ice, and geomorphological processes of mass wasting, erosion and sedimentation. Here we explore the relation between a 3 year data set of InSAR measurements of vertical surface displacements during the thaw season, and geomorphological features in an area in the Indigirka Lowlands, Northeast Siberia. The geomorphology is presented in a geomorphological map, based on interpretation of high resolution visible spectrum satellite imagery, field surveys and available data from paleo-environmental research. The main landforms comprise overlapping drained thaw lake basins and lakes, erosion remnants of Late Pleistocene Yedoma deposits, and a floodplain of a high-sinuosity anastomosing river with ancient river terrace remnants. The spatial distribution of drained thaw lake basins and Yedoma erosion remnants in the study area and its surroundings is influenced by neotectonic movements. The 3 years of InSAR measurement include 2 years of high snowfall and extreme river flooding (2017–2018) and 1 year of modest snowfall, early spring and warm summer (2019). The magnitude of surface displacements varies among the years, and show considerable spatial variation. Distinct spatial clusters of displacement trajectories can be discerned, which relate to geomorphological processes and ground ice conditions. Strong subsidence occurred in particular in 2019. In the wet year of 2017, marked heave occurred at Yedoma plateau surfaces, likely by ice accumulation at the top of the permafrost driven by excess precipitation. The spatial variability of surface displacements is high. This is explored by statistical analysis, and is attributed to the interaction of various processes. Next to ground ice volume change, also sedimentation (peat, colluvial deposition) and shrinkage or swelling of soils with changing water content may have contributed. Tussock tundra areas covered by the extreme 2017 and 2018 spring floods show high subsidence rates and an increase of midsummer thaw depths. We hypothesize that increased flood heights along Siberian lowland rivers potentially induce deeper thaw and subsidence on floodplain margins, and also lowers the drainage thresholds of thaw lakes. Both mechanisms tend to increase floodplain area. This may increase CH4 emission from floodplains, but also may enhance carbon storage in floodplain sedimentary environments.

Towards accurate quantification of ice content in permafrost of the Central Andes, part I: geophysics-based estimates from three different regions

In view of the increasing water scarcity in the Central Andes in response to ongoing climate change, the significance of permafrost occurrences for the hydrological cycle is currently being discussed in a controversial way. The lack of comprehensive field measurements and quantitative data on the local variability of internal structure and ground ice content further enhances the situation. We present field-based data from six extensive geophysical campaigns completed since 2016 in three different high-altitude regions of the Central Andes of Chile and Argentina (28 to 32° S). Our data cover various permafrost landforms ranging from ice-poor bedrock to ice-rich rock glaciers and are complemented by ground truthing information from boreholes and numerous test pits near the geophysical profiles. In addition to determining the thickness of the potential ice-rich layers from the individual profiles, we also use the quantitative 4-phase model to estimate the volumetric ground ice content in representative zones of the geophysical profiles. The analysis of 52 geoelectrical and 24 refraction seismic profiles within this study confirmed that ice-rich permafrost is not restricted to rock glaciers, but is also observed in non-rock-glacier permafrost slopes in the form of interstitial ice as well as layers with excess ice, resulting in substantial ice contents. Consequently, non-rock glacier permafrost landforms, whose role for local hydrology has so far not been considered in remote-sensing based approaches, may be similarly relevant in terms of ground ice content on a catchment scale and should not be ignored when quantifying the potential hydrological significance of permafrost. We state that geophysics-based estimates on ground ice content allow for more accurate assessments than purely remote-sensing-based approaches. The geophysical data can then be further used in upscaling studies to the catchment scale in order to reliably estimate the hydrological significance of permafrost within a catchment.