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Here, we present empirical ground penetrating radar (GPR) and electroresistivity tomography data (ERT) to verify the cold-temperate transition surface-permafrost base (CTS-PB) axis theoretical model. The data were collected from S...
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Here, we present empirical ground penetrating radar (GPR) and electroresistivity tomography data (ERT) to verify the cold-temperate transition surface-permafrost base (CTS-PB) axis theoretical model. The data were collected from Storglaciaren, in Tarfala, Northern Sweden, and its forefield. The GPR results show a material relation between the glacial ice and the sediments incorporated in the glacier, and a geophysical relation between the cold ice and the temperate ice layers. Clearly identifying lateral glacier margins is difficult, as periglacial and glacial environments frequently overlap. In this case, we identified areas showing permafrost aggradation already under the glacier, particularly where the CTS is replaced by the PB surface. This structure appears as a result of the influence of a cold climate over both the glacial and periglacial environments. The results show how these surfaces form a specific continuous environmental axis; thus, both glacial and periglacial areas can be treated uniformly as a specific continuum in the geophysical sense. Similarly, other examples previously described also allow identifying a continuation of permafrost from the periglacial environment onto the glacial base. In addition, the ERT results show the presence of double-layered periglacial permafrost, possibly suggesting a past climatic fluctuation in the study area.
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Since 2002, ground and ground surface temperatures have been systematically measured in the mountains of Troms and Finnmark, northern Norway. These data were used to calibrate and validate a transient heat flow model and a spatial...
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Since 2002, ground and ground surface temperatures have been systematically measured in the mountains of Troms and Finnmark, northern Norway. These data were used to calibrate and validate a transient heat flow model and a spatial permafrost model, to address ground thermal development since the end of the Little Ice Age, as well as possible permafrost responses to anticipated future climate changes. Approximately 20 per cent of the land area is underlain by permafrost, and in Finnmark, permafrost in palsa mires seems to dominate. Both observations and modelling show that the present permafrost is mainly 'warm', with mean ground temperatures above -3 °C. Permafrost has warmed during the last century, and at one site our ground temperature observations show the degradation of permafrost over the intervening decade. The study identifies three major permafrost regions in northern Norway: (1) maritime mountain permafrost in western Troms; (2) continental permafrost above the treeline and in bogs in Finnmark; and (3) Low Arctic permafrost on the peninsula of Varangerhalv0ya, forming a transition between the Scandinavian mountain-dominated permafrost in the south and the arctic permafrost towards the north and east.
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In order to specify potentially causal relationships between climate, permafrost extent and sea-ice cover we apply a twofold research strategy: (1) we cover a large range of climate conditions varying from full glacial to the rela...
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In order to specify potentially causal relationships between climate, permafrost extent and sea-ice cover we apply a twofold research strategy: (1) we cover a large range of climate conditions varying from full glacial to the relatively warm climate projected for the end of the 21st Century, (2) we combine new proxy-based reconstructions of Eurasian permafrost extent during the LGM and climate model simulations. We find that that there is a linear relationship between the winter sea-ice extent in the North Atlantic and Arctic Oceans and the latitude of the southernmost permafrost limit in Eurasia. During the LGM, extensive sea-ice cover caused a zonal permafrost distribution with the southern margin extending W-E and reaching 47°N, contrasting with the present-day NW-SE trending margin (66°-52°N). We infer that under global warming scenarios projected by climate models for the 21st Century the Arctic sea-ice cover decline will cause widespread instability of, mainly discontinuous, permafrost in Eurasian lowlands.
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The properties, distribution patterns and thermal processes that influence the active layer and permafrost in the Transantarctic Mountains region of Antarctica, as deduced from our soil investigations since 1964 and drilling inves...
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The properties, distribution patterns and thermal processes that influence the active layer and permafrost in the Transantarctic Mountains region of Antarctica, as deduced from our soil investigations since 1964 and drilling investigations since 1990, are outlined. The active layer depth varies from around 80 cm thick in coastal areas to < 5 cm in inland and upland regions, due to the effect of the adiabatic lapse rate. Saline, ice-bonded, dry permafrost and transitional types of permafrost all occur. Ice content is highest in ice-bonded permafrost of the coastal regions and lowest in inland dry permafrost where values may be < 1%. At the regional scale, ice-bonded permafrost most commonly occurs at lower elevations and beneath younger land surfaces but with increasing elevation, distance inland and land surface age, dry permafrost becomes predominant. At the local scale (< 1 m) there are large variations in the depth to the permafrost table due to variations in ground surface features. Permafrost properties are largely governed by solar energy receipt, but albedo, air temperature cooling and available soil moisture strongly modulate the conversion of solar energy receipt into soil heating. These factors account for the considerable broad-scale and local variability in permafrost properties that exists.
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This paper reviews recent literature, published between 2002 and 2007, concerning the previous existence of permafrost (past permafrost) that formed during the cold periods of the Pleistocene in the northern mid-latitudes. Some pa...
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This paper reviews recent literature, published between 2002 and 2007, concerning the previous existence of permafrost (past permafrost) that formed during the cold periods of the Pleistocene in the northern mid-latitudes. Some past permafrost continues to be preserved today as relict permafrost in the higher northern latitudes. Given that global climate warming models predict widespread thaw of permafrost in the coming century, it is surprising that little attention has been given to the insights that past and relict permafrost offer as to the nature and duration of permafrost thaw.
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Abstract The Antarctic continent is a crucial area for ultimate determination of permafrost extent on Earth, and its solution depends on the theoretical assumptions adopted. In fact, it ranges from 0.022 × 106 to 14 × 106 k...
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Abstract The Antarctic continent is a crucial area for ultimate determination of permafrost extent on Earth, and its solution depends on the theoretical assumptions adopted. In fact, it ranges from 0.022 × 106 to 14 × 106 km2. This level of inaccuracy is unprecedented in the Earth sciences. The novelty of the present study consists in determining the extent of Antarctic permafrost not based exclusively on empirical studies but on universal criteria resulting from the definition of permafrost as the thermal state of the lithosphere, which was applied for the first time to this continent. The area covered by permafrost in Antarctica is ca. 13.9 million km2, that is its entire surface. This result was also made possible due to the first clear determination of the boundaries and area of the continent. The Antarctic area includes (a) rocky subsurface with (b) continental ice‐sheets and (c) shelf glaciers, which, due to their terrigenous origin and belonging to the lithosphere, belongs to the continent in the same way. Antarctica is covered by continuous permafrost, either in a frozen or in a cryotic state. This also significantly influences delimitation of the global extent of permafrost, which can therefore be defined much more accurately. The proposed ice reclassification and its transfer from the hydrosphere to the lithosphere will allow the uniform treatment of ice in the Earth sciences, both on Earth and on other celestial bodies.
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Abstract In continuous permafrost regions, pathways for transport of sub‐permafrost groundwater to the surface sometimes perforate the frozen ground and result in the formation of a pingo. Explanations offered for the locations o...
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Abstract In continuous permafrost regions, pathways for transport of sub‐permafrost groundwater to the surface sometimes perforate the frozen ground and result in the formation of a pingo. Explanations offered for the locations of such pathways have so far included hydraulically conductive geological units and faults. On Svalbard, several pingos locate at valley flanks where these controls are apparently lacking. Intrigued by this observation, we elucidated the geological setting around such a pingo with electrical resistivity tomography. The inverted resistivity models showed a considerable contrast between the uphill and valley‐sides of the pingo. We conclude that this contrast reflects a geological boundary between low‐permeable marine sediments and consolidated strata. Groundwater presumably flows toward the pingo spring through glacially induced fractures in the strata immediately below the marine sediments. Our finding suggests that flanks of uplifted Arctic valleys deserve attention as possible discharge locations for deep groundwater and greenhouse gases to the surface.
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A research-based understanding of permafrost distribution at a sufficient spatial resolution is important to meet the demands of science, education and society. We present a new permafrost map for Norway, Sweden and Finland that p...
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A research-based understanding of permafrost distribution at a sufficient spatial resolution is important to meet the demands of science, education and society. We present a new permafrost map for Norway, Sweden and Finland that provides a more detailed and updated description of permafrost distribution in this area than previously available. We implemented the CryoGRID1 model at 1km(2) resolution, forced by a new operationally gridded data-set of daily air temperature and snow cover for Finland, Norway and Sweden. Hundred model realisations were run for each grid cell, based on statistical snow distributions, allowing for the representation of sub-grid variability of ground temperature. The new map indicates a total permafrost area (excluding palsas) of 23 400km(2) in equilibrium with the average 1981-2010 climate, corresponding to 2.2 per cent of the total land area. About 56 per cent of the area is in Norway, 35 per cent in Sweden and 9 per cent in Finland. The model results are thoroughly evaluated, both quantitatively and qualitatively, as a collaboration project including permafrost experts in the three countries. Observed ground temperatures from 25 boreholes are within +/- 2 degrees C of the average modelled grid cell ground temperature, and all are within the range of the modelled ground temperature for the corresponding grid cell. Qualitative model evaluation by field investigators within the three countries shows that the map reproduces the observed lower altitudinal limits of mountain permafrost and the distribution of lowland permafrost. Copyright (c) 2016 John Wiley & Sons, Ltd.
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Permafrost thaw and its impacts on ecosystem carbon (C) dynamics are critical for predicting global climate change. It remains unclear whether annual and seasonal warming (winter or summer) affect permafrost thaw and ecosystem C b...
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Permafrost thaw and its impacts on ecosystem carbon (C) dynamics are critical for predicting global climate change. It remains unclear whether annual and seasonal warming (winter or summer) affect permafrost thaw and ecosystem C balance differently. It is also required to compare the short-term stepwise warming and long-term gradual warming effects. This study validated a land surface model, the Community Atmosphere Biosphere Land Exchange model, at an Alaskan tundra site, and then used it to simulate permafrost thaw and ecosystem C flux under annual warming, winter warming, and summer warming. The simulations were conducted under stepwise air warming (2℃ yr~(-1)) during 2007-2011, and gradual air warming (0.04℃ yr~(-1)) during 2007-2056. We hypothesized that all warming treatments induced greater permafrost thaw, and larger ecosystem respiration than plant growth thus shifting the ecosystem C sink to C source. Results only partially supported our hypothesis. Climate warming further enhanced C sink under stepwise (6-15%) and gradual (1-8%) warming scenarios as followed by annual warming, winter warming, and summer warming. This is attributed to disproportionally low temperature increase in soil (0.1℃) in comparison to air warming (2℃). In a separate simulation, a greater soil warming (1.5℃ under winter warming) led to a net ecosystem C source (i.e., 18 g Cm~(-2) yr~(-1)). This suggests that warming tundra can potentially provide positive feedbacks to global climate change. As a key variable, soil temperature and its dynamics, especially during wintertime, need to be carefully studied under global warming using both modeling and experimental approaches.
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