Thermokarst Subsidence Research Articles

Late Quaternary persistent impacts of permafrost on lake hydrology and landscape evolution on the NE Tibetan Plateau

Permafrost on the Tibetan Plateau (TP) plays an important role on influencing regional to local hydrology of lake systems by thermokarst processes. Rare investigations and research of such process variations and how they affect persistently the water budget and landscape cratering in alpine lake basin through the Late Quaternary are reported. We used Lake Heihai on the north-eastern Tibetan Plateau as an example to reveal how landscape change/collapse under the regime of permafrost and thermokarst processes occurred since the Lateglacial. Five shallow seismic profiles in combination with lake core sediments from the lake centre as well as fossil lacustrine deposits in the catchment were obtained and analysed by multiple proxies. The results show that Lake Heihai did not exist as a terminal lake during the Lateglacial and the beginning of the early Holocene with widespread permafrost in the basin. Permafrost thaw and glacier melt of short duration contributed to lake hydrology and sediment accumulation. Thermokarst development started in the early Holocene with climate warming and increased water storage in the shallow basin, finally enabling the onset of a thermokarst lake with subsidence of lake deposits. Thermokarst thaw contributed reworked materials to the lake during the formation of a growing talik layer beneath the lake. The damming of the previous outflow in the east by glacio-fluvial accumulation initiated a closed system, combined with the accelerated thermokarst subsidence, which promoted a rapid lake level rise during the middle Holocene, mainly supplied by glacier melt. This period was characterized by the withdrawal of permafrost to higher position in the catchment. Lake Heihai became open again after around 5.3 ka and initiated a significant shrinkage culminating at around 4 cal ka BP and lasted until 2.4 cal ka BP. Permafrost returned into the exposed middle Holocene lacustrine sediments which were then subject to strong seasonal thaw-induced erosion and back transport into the lake, while water depth increased to the present level with returned thermokarst processes at the lake margin. Recent occurrences and disappearances of permafrost phenomena near shore, such as lithalsa/pingos, might have existed in the past as well. Our research sheds new light on the long-lasting impacts of permafrost on the hydrological cycle and integrated landscape evolution in a lake basin on the Tibetan Plateau.

Surface displacement revealed by L-band InSAR analysis in the Mayya area, Central Yakutia, underlain by continuous permafrost

Recent increases in global temperature have stimulated permafrost degradation associated with landform deformation caused by the melting of excess ground ice (thermokarst). Central Yakutia is underlain by ice-rich continuous permafrost, and there are complicated permafrost-related features in forested and deforested areas. This situation makes thermokarst monitoring necessary over a wide area to achieve a better understanding of its dynamics. As a case study, we applied L-band InSAR analysis to map surface subsidence due to thermokarst in this area and to demonstrate the suitability of L-band SAR for such monitoring. Our results show that InSAR detected subsidence/uplift signals in deforested areas and alasses; whereas, there were few ground deformation signals in forested areas with middle coherence. The InSAR stacking process, including both seasonal and inter-annual displacements, showed subsidence in deforested areas during 2007–2010 and 2015–2018, in the range of 0.5–3 cm yr−1. We also estimated the inter-annual subsidence to be up to 2 cm yr−1 during 2015–2018, using InSAR pairs that spanned the same seasonal interval but in different years. The magnitude of subsidence and the spatial patterns are qualitatively reasonable as thermokarst subsidence compared to observations using field surveys and high-resolution optical images. L-band InSAR was effective in maintaining coherence over a long period for a partially forested thermokarst-affected area, which resulted in deriving the inter-annual subsidence by the stacking using four interferograms. The advantage of the persistent coherence in L-band InSAR is crucial to better understand thermokarst processes in permafrost regions.

Tracking of areas of thermokarst occurrences from satellite images (on the example of the main water pipeline route in Central Yakutia)

  In the areas of distribution of permafrost rocks and development of the ice complex, lake thermokarst is the main relief-forming process, which forms a characteristic alas relief. In addition to the formation of lakes, as a result of thermokarst subsidence, accompanied by water runoff, forms the thermo-sculptured relief including Baydzharakh and hummock-hollow forms. This leads to formation of thermokarst occurrences. The object of this research is thermokarst occurrences, namely, polygonal microrelief and frost splitting, explored in the section of the main water pipeline “Lena – Tuora-Kyuel – Tatta”, near the settlement of Maya Megino-Kangalassky Ulus of the Sakha Republic (Yakutia). These thermokarst occurrences were identified from the satellite images that are publicly available on the Internet. The author also applied processing technique of engineering and geological data, literary and library materials were also used in the work. Field research and simple photography were also used for determining the shape and size polygons. The main conclusion consists in suggesting simple method that allows to conduct area zoning of the territory for activation of the polygonal microrelief as thermokarst occurrences. The research results of area zoning related to distribution of cryogenic processes can be used in technical-economic substantiation of the choice of routes of linear and other constructs.  

Decadal topographic change in the McMurdo Dry Valleys of Antarctica: Thermokarst subsidence, glacier thinning, and transfer of water storage from the cryosphere to the hydrosphere

Recent local-scale observations of glaciers, streams, and soil surfaces in the McMurdo Dry Valleys of Antarctica (MDV) have documented evidence for rapid ice loss, glacial thinning, and ground surface subsidence associated with melting of ground ice. To evaluate the extent, magnitude, and location of decadal-scale landscape change in the MDV, we collected airborne lidar elevation data in 2014–2015 and compared these data to a 2001–2002 airborne lidar campaign. This regional assessment of elevation change spans the recent acceleration of warming and melting observed by long-term meteorological and ecosystem response experiments, allowing us to assess the response of MDV surfaces to warming and potential thawing feedbacks. We find that locations of thermokarst subsidence are strongly associated with the presence of excess ground ice and with proximity to surface or shallow subsurface (active layer) water. Subsidence occurs across soil types and landforms, in low-lying, low-slope areas with impeded drainage and also high on steep valley walls. Glacier thinning is widespread and is associated with the growth of fine-scale roughness. Pond levels are rising in most closed-basin lakes in the MDV, across all microclimate zones. These observations highlight the continued importance of insolation-driven melting in the MDV. The regional melt pattern is consistent with an overall transition of water storage from the local cryosphere (glaciers, permafrost) to the hydrosphere (closed basin lakes and ponds as well as the Ross Sea). We interpret this regional melting pattern to reflect a transition to Arctic and alpine-style, hydrologically mediated permafrost and glacial melt.

Geomorphological and geochemistry changes in permafrost after the 2002 tundra wildfire in Kougarok, Seward Peninsula, Alaska

AbstractGeomorphological and thermohydrological changes to tundra, caused by a wildfire in 2002 on the central Seward Peninsula of Alaska, were investigated as a case study for understanding the response from ice‐rich permafrost terrain to surface disturbance. Frozen and unfrozen soil samples were collected at burned and unburned areas, and then water isotope geochemistry and cryostratigraphy of the active layer and near‐surface permafrost were analyzed to investigate past hydrological and freeze/thaw conditions and how this information could be recorded within the permafrost. The development of thermokarst subsidence due to ice wedge melting after the fire was clear from analyses of historical submeter‐resolution remote sensing imagery, long‐term monitoring of thermohydrological conditions within the active layer, in situ surveys of microrelief, and geochemical signals recorded in the near‐surface permafrost. The resulting polygonal relief coincided with depression lines along an underground ice wedge network, and cumulative subsidence to 2013 was estimated as at least 10.1 to 12.1 cm (0.9–1.1 cm/year 11 year average). Profiles of water geochemistry in the ground indicated mixing or replenishment of older permafrost water with newer meteoric water, as a consequence of the increase in active layer thickness due to wildfire or past thaw event. Our geocryological analysis of cores suggests that permafrost could be used to reconstruct the permafrost degradation history for the study site. Distinct hydrogen and oxygen isotopic compositions above the Global Meteoric Water Line were found for water from these sites where permafrost degradation with geomorphological change and prolonged surface inundation were suggested.

Active-Layer Thickness Measurements Using a Handheld Penetrometer at Boreal and Tundra Sites in Eastern Siberia

Active-layer thickness (ALT) is one of the most robust measures used to assess the impact of climate change on terrestrial permafrost. Testing of a handheld dynamic cone penetrometer showed that it was capable of measuring ALT with the same level of accuracy as conventional methods in boreal and tundra sites in eastern Siberia. The penetrometer also characterised the vertical structure of ground hardness within the active layer. The vertical profile of penetrometer measurements corresponded closely with soil plasticity and the liquid limit in high-centred polygons produced by thermokarst subsidence in dry grassland areas at a boreal site at Churapcha. The ALT was markedly deeper (>70 cm) at gravelly slope points adjacent to a wet tundra plain (<50 cm) in a CALM grid (R8) at Tiksi. Overall, the penetrometer is considered to provide an accurate and informative proxy for rapidly assessing the spatial heterogeneity and interannual changes in ALT. 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.

Remote sensing measurements of thermokarst subsidence using InSAR

AbstractThawing of ice‐rich permafrost followed by surface subsidence results in irregular, depressed landforms known as thermokarst. Many remote sensing studies have identified thermokarst landforms and mapped their changes. However, the intrinsic dynamic thermokarst process of surface subsidence remains a challenge to quantify and is seldom examined using remote sensing methods. In this study we used spaceborne interferometric synthetic aperture radar (InSAR) data to map surface subsidence trends at a thermokarst landform located near Deadhorse on the North Slope of Alaska. A pipeline access road constructed in the 1970s triggered the thawing of the permafrost, causing subsequent expansion of the thermokarst landform. Using Phased Array type L band Synthetic Aperture Radar images acquired by the Advanced Land Observing Satellite‐1, our InSAR analysis reveals localized thermokarst subsidence of 2–8 cm/yr between 2006 and 2010, equivalent to an ice volume loss of about 1.2 × 107 m3/yr. Comparisons between InSAR subsidence trends and lidar microtopography suggest a characteristic time of 8 years of thermokarst development. We also quantitatively explain the difficulty, uncertainties, and possible biases in separating thermokarst‐induced, irreversible subsidence from cyclic seasonal deformation. Our study illustrates that InSAR is an effective tool for mapping and studying active thermokarst processes and quantifying ice loss.

Sap flow changes in relation to permafrost degradation under increasing precipitation in an eastern Siberian larch forest

ABSTRACTContinuous observation over the last decade has revealed evidence of abrupt land surface moistening as well as rapid soil warming within the active layer and upper part of permafrost within the central Lena River basin in eastern Siberia. The present study examined the relationship between permafrost degradation and ecohydrological change in this region. Increases in the depth of the active layer recorded since the winter of 2004 resulting from increases in moisture saturation within the soil have resulted in thawing the upper permafrost causing thermokarst subsidence, which has negatively impacted the growth of boreal (larch) forests in the region. According to multi‐year sap flow measurements taken between 2006 and 2009, transpiration from larch trees (Larix cajanderi Mayr.) was significantly reduced as a result of the region's concave micro‐topography, which, in conjunction with the deepening and moistening of the active layer, created perennially waterlogged conditions that left mature trees withered and dead. Several trees with reduced amounts of foliage showed a remarkable reduction in seasonal average canopy stomatal conductance during the 2009 growing season. The reduction ratio of canopy stomatal conductance within emergent trees of heights greater than 15 m between 2006 and 2009 had a significant positive correlation with the increase in thickness of the active layer over that same period. These findings indicated that wetting trends in a permafrost region caused by arctic climate change may lead to unexpected ecohydrological responses with respect to permafrost degradation in eastern Siberia. Copyright © 2013 John Wiley &amp; Sons, Ltd.

周氷河地形プロセス研究最前線

Periglacial process studies, which began in the mid-20th century, have greatly advanced in recent years following several breakthroughs. This paper reviews the latest breakthroughs supported by new technologies, themes, and international projects. New technologies have enabled small, high-resolution data loggers to monitor rock and soil movements, and thermal and hydrological properties in polar and alpine areas; enabled geophysical instruments to visualize two- and three- dimensional subsurface structures below periglacial features; and, enabled numerical simulations to predict future landform evolution. In particular, dramatic progress has been achieved in understanding bedrock shattering and falls, soil movements induced by freeze-thaw oscillations, controls on rock glacier creep, critical conditions for ice-wedge cracking, and biogeophysical impacts on non-sorted circles. Two key words, global warming and Mars, are appearing often in periglacial research. High mountains and polar lowlands face the fate of potential natural hazards associated with rock slides, debris flows and thermokarst subsidence, possibly originating from permafrost thawing. High-resolution orbital images and on-site explorations on Mars provide detailed information on small-scale, potential periglacial features, which are the morphologically equivalent of terrestrial counterparts. International collaboration is expected to further promote modeling various periglacial features on a global scale, improve the resolutions of periglacial climate indicators, and increase understanding of past and present Martian environments.

Geological and geomorphological evolution of a sedimentary periglacial landscape in Northeast Siberia during the Late Quaternary

A wide variety of environmental records is necessary for analysing and understanding the complex Late Quaternary dynamics of permafrost-dominated Arctic landscapes. A NE Siberian periglacial key region was studied in detail using sediment records, remote sensing data, and terrain modelling, all incorporated in a geographical information system (GIS). The study area consists of the Bykovsky Peninsula and the adjacent Khorogor Valley in the Kharaulakh Ridge situated a few kilometres southeast of the Lena Delta. In this study a comprehensive cryolithological database containing information from 176 sites was compiled. The information from these sites is based on the review of previously published borehole data, outcrop profiles, surface samples, and our own field data. These archives cover depositional records of three periods: from Pliocene to Early Pleistocene, the Late Pleistocene and the Holocene. The main sediment sequences on the Bykovsky Peninsula consist of up to 50 m thick ice-rich permafrost deposits (Ice Complex) that were accumulated during the Late Pleistocene. They were formed as a result of nival processes around extensive snowfields in the Kharaulakh Ridge, slope processes in these mountains (such as in the Khorogor Valley), and alluvial/proluvial sedimentation in a flat accumulation plain dominated by polygonal tundra in the mountain foreland (Bykovsky Peninsula). During the early to middle Holocene warming, a general landscape transformation occurred from an extensive Late Pleistocene accumulation plain to a strongly thermokarst-dominated relief dissected by numerous depressions. Thermokarst subsidence had an enormous influence on the periglacial hydrological patterns, the sediment deposition, and on the composition and distribution of habitats. Climate deterioration, lake drainage, and talik refreezing occurred during the middle to late Holocene. The investigated region was reached by the post-glacial sea level rise during the middle Holocene, triggering thermo-abrasion of ice-rich coasts and the marine inundation of thermokarst depressions.

Landf orms and Coastal Retreat in Relation to Thawing of ^|^ldquo;Edoma^|^rdquo; on Southern Coast of Bolshoi Lyakhovsky Island, Northeastern Siberia

The characteristics of landforms and coastal retreat resulting from thawing of permafrost called edoma, which is widely distributed along the Arctic coast in northeastern Siberia, are discussed. Edoma is composed of massive ground ice containing evenly scattered frozen soil pillars, and underlain by ice-poor silty sediments, The meteorological data at some adjacent locations indicate that thawing is active from mid June to mid September. Four landform units: upper flat, upper cliff, middle gentle slope, and lower cliff, are recognized from inland to seaside near the coastline on which edoma is exposed. Upper flat roughly corresponds with the top of the edoma, while many mounds formed by thermokarst subsidence are scattered on it. Thawing of edoma is extremely active on the upper cliff, and consequently the cliff itself retreats. Although much microtopography indicating active thawing of edoma is widespread on the middle gentle slope, downward thermal erosion seems to become ineffective in the lower horizon of edoma because the underlayer of edoma consists of ice-poor silt which does not suffer considerable morphological change by thawing. The lower cliff which directly faces the sea is exposed to thermal erosion by waves, and a notch is successively formed at the base. Sudden coastal retreat amounting to several meters is expected after the notch becomes deep enough to collapse. These processes are controlled by the characteristics of material, structure, and stratigraphy of the permafrost in this area.

The origin of fluvial valleys and early geologic history, Aeolis Quadrangle, Mars

In southern Aeolis Quadrangle in eastern Mars, parallel slope valleys, flat‐floored branching valleys, V‐shaped branching valleys, and flat‐floored straight canyons dissect the heavily cratered plateau sequence. Associated knife‐like ridges are interpreted as fissure eruption vents, and thin, dark, stratiform outcrops are interpreted as exhumed igneous sills or lava flows. Ridged lava plains are also common but are not themselves modified by fluvial processes. I mapped 56 asymmetric scarps or ridges that are probable thrust faults. These faults exhibit an orientation vector mean of N63°W±11° (95% confidence interval), and they transect the lava plains and the older plateau sequence units. By comparison, the vector mean for the 264 valleys mapped is N48°W±12°, with a larger dispersion about the mean. The similar orientations displayed by thrust fault and valley axes suggest that valley locations are partly controlled by preexisting thrust faults and related fracture systems. Most valleys are also arranged orthogonally to, and along the perimeter of, the ridged plains. A possible model for valley development is: (1) freshly outgassed water became entombed as frost, snow, and ice within the cratered terrains during heavy bombardment and the accompanying deposition of impact ejecta, volcanic ash, and eolian materials, (2) effusive volcanism and lava sill emplacement heated subsurface ice in the vicinity of the ridged plains, and faults and fractures provided zones of increased permeability for water transport to the surface, and (3) headward sapping at thermal springs, thermokarst subsidence, and limited downvalley fluid flows then carved and modified the valleys.

Occurrence of permafrost on the Varanger Peninsula, northeasternmost Norway

Increased interest in periglacial conditions has resulted in a more thorough knowledge of the distribution of permafrost. The Varanger Peninsula, northeasternmost Norway, is commonly placed in the zone of sporadic permafrost. The occurrence of permafrost on the peninsula is discussed on the basis of a geomorphological map and temperature data. The map includes areas of thermokarst subsidence reported here for the first time from this area. The discussion indicates the presence of areas of permafrost outside the mires, especially in the central parts of the peninsula.

Gravity Profiles across Ice-Cored Topography

Gravity profiling at five different sites in an area of ice-cored topography indicates the usefulness of the technique as a method for the detection of ground ice and for estimating the thickness of the excess ice. Bouguer anomaly profiles using a density of 2.0 Mgm−3 provide a quick method of assessing the relative amount of ice along a profile, the thickness of ice and the elevation being inversely proportional to the Bouguer anomaly value along each profile. The average amount of excess ice in the topography along the profiles is obtained by removing linear trends, obtaining the Bouguer density of the topography, and calculating the proportion of frozen saturated sediment and ice required to produce this density. Variations in the thickness of the body are obtained from significant gravity residuals. Finally, models are given to show the distribution of the excess ice with the aid of supplementary information. The above technique is unable to detect changes in the amount of excess ice that have a linear trend over the complete profile or a uniform slab of ice underlying the complete profile. A model for a pingo is constructed using stacked concentric cylinders. Geologic data from the region indicate that all models give reliable estimates of the amount of excess ice and probable thermokarst subsidence if the area were thawed.

Natural plant recolonization of surficial disturbances, Tuktoyaktuk Peninsula Region, Northwest Territories

Seismic lines or winter roads were sampled where they passed through three different plant communities in the Mackenzie Delta and through four of the major tundra communities in the Tuktoyaktuk Peninsula. Winter seismic lines have been less detrimental than summer lines for all communities examined. Although winter roads through upland areas remove most of the vegetation cover, the peat layer usually remains intact and soil energy budgets are relatively little affected. Wetland sedge meadows are highly susceptible to summer disturbance but least affected by winter operations. Winter-disturbed forested and tall shrub communities recover faster initially than similarly disturbed upland tundra communities.Eriophorum vaginatum and Carex bigelowii appeared to be stimulated by disturbances which did not eliminate them, with Eriophorum often flowering more abundantly in disturbed areas. This probably results from warmer soils and greater nutrient uptake.Summer seismic lines (1965), originally bladed to permafrost, resulted in exposure of mineral soil and thus led to secondary succession in tundra communities. Arctagrostis latifolia, Calamagrostis canadensis, Poa arctica, and Luzula confusa are the most typical and abundant pioneers of upland mesic sites. Wet sites are colonized predominantly by Arctophila fulva and Carex aquatilis. Once established, these species expanded rhizomatously. Six years after exposure of mineral soil, plant cover was usually 30 to 50%.Thaw was generally increased 80 to 100% where mineral soil was exposed, 30 to 50% if the peat remained intact, and 10% if plant cover was little altered. Subsurface ice has occasionally been exposed, resulting in thermokarst subsidence. Water erosion has not been a factor, probably because of the low precipitation in the region.

Disturbances to the tundra and forest tundra environment of the western Arctic

The more important physical disturbances to the tundra environment are discussed with examples. Thermokarst subsidence, not thermal erosion, is shown to be the dominant result of man-induced disturbances, such as those caused by the bulldozing of seismic lines and firebreaks. It is shown that a clear distinction between thermokarst subsidence and thermal erosion is necessary, if the causes of the disturbances are to be prevented and minimized, or the results treated. The typical surface disturbance to the tundra results in a deepening of the active layer. Therefore, foreknowledge of the effect of a disturbance on deepening the active layer, together with information on the ice content of the permafrost affected, makes it possible to predict the amount of thermokarst subsidence likely to take place. Three practical examples of three types of ground disturbance are given: a fire near Inuvik, N.W.T.; a patch of vegetation trampled and killed by a dog at Garry Island, N.W.T.; and seepage down a walking trail in an ice-wedge area at Garry Island, N.W.T. The effects of the disturbances are illustrated and discussed.