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Permafrost Zone (permafrost + zone)

Distribution by Scientific Domains

Earth and Environmental Science	27%

Selected Abstracts

Permafrost thermal state in the polar Northern Hemisphere during the international polar year 2007,2009: a synthesis

PERMAFROST AND PERIGLACIAL PROCESSES, Issue 2 2010
Vladimir E. Romanovsky
Abstract The permafrost monitoring network in the polar regions of the Northern Hemisphere was enhanced during the International Polar Year (IPY), and new information on permafrost thermal state was collected for regions where there was little available. This augmented monitoring network is an important legacy of the IPY, as is the updated baseline of current permafrost conditions against which future changes may be measured. Within the Northern Hemisphere polar region, ground temperatures are currently being measured in about 575 boreholes in North America, the Nordic region and Russia. These show that in the discontinuous permafrost zone, permafrost temperatures fall within a narrow range, with the mean annual ground temperature (MAGT) at most sites being higher than ,2°C. A greater range in MAGT is present within the continuous permafrost zone, from above ,1°C at some locations to as low as ,15°C. The latest results indicate that the permafrost warming which started two to three decades ago has generally continued into the IPY period. Warming rates are much smaller for permafrost already at temperatures close to 0°C compared with colder permafrost, especially for ice-rich permafrost where latent heat effects dominate the ground thermal regime. Colder permafrost sites are warming more rapidly. This improved knowledge about the permafrost thermal state and its dynamics is important for multidisciplinary polar research, but also for many of the 4 million people living in the Arctic. In particular, this knowledge is required for designing effective adaptation strategies for the local communities under warmer climatic conditions. Copyright © 2010 John Wiley & Sons, Ltd. [source]

Patterns of permafrost formation and degradation in relation to climate and ecosystems

PERMAFROST AND PERIGLACIAL PROCESSES, Issue 1 2007
Y. L. Shur
Abstract We develop a permafrost classification system to describe the complex interaction of climatic and ecological processes in permafrost formation and degradation that differentiates five patterns of formation: ,climate-driven'; ,climate-driven, ecosystem-modified'; ,climate-driven, ecosystem-protected'; ,ecosystem-driven'; and ,ecosystem-protected' permafrost. Climate-driven permafrost develops in the continuous permafrost zone, where permafrost forms immediately after the surface is exposed to the atmosphere and even under shallow water. Climate-driven, ecosystem-modified permafrost occurs in the continuous permafrost zone when vegetation succession and organic-matter accumulation lead to development of an ice-rich layer at the top of the permafrost. During warming climates, permafrost that has formed as climate-driven can occur in the discontinuous permafrost zone, where it can persist for a long time as ecosystem-protected. Climate-driven, ecosystem protected permafrost, and its associated ground ice, cannot re-establish in the discontinuous zone once degraded, although the near surface can recover as ecosystem-driven permafrost. Ecosystem-driven permafrost forms in the discontinuous permafrost zone in poorly drained, low-lying and north-facing landscape conditions, and under strong ecosystem influence. Finally, ecosystem-protected permafrost persists as sporadic patches under warmer climates, but cannot be re-established after disturbance. These distinctions are important because the various types react differently to climate change and surface disturbances. For example, climate-driven, ecosystem-modified permafrost can experience thermokarst even under cold conditions because of its ice-rich layer formed during ecosystem development, and ecosystem-driven permafrost is unlikely to recover after disturbance, such as fire, if there is sufficient climate warming. Copyright © 2007 John Wiley & Sons, Ltd. [source]

Mountain permafrost distribution modelling using a multi-criteria approach in the Hövsgöl area, northern Mongolia,,

PERMAFROST AND PERIGLACIAL PROCESSES, Issue 2 2006
Bernd Etzelmüller
Abstract Lake Hövsgöl is located on the southern fringe of the continuous permafrost zone in northern Mongolia. This paper describes a GIS-based empirical permafrost model that is calibrated with ground temperature observations, and utilises a multi-criteria approach to derive zones of permafrost favourability based on terrain parameters and land cover information. The scores are derived either by logistic regression or from satellite image information. The model is validated by DC resistivity tomography measurements. The overall permafrost distribution in the study area is well-described and the method appears to be a valid approach for mapping permafrost at both local and regional scales in mountain areas with low data coverage. Copyright © 2006 John Wiley & Sons, Ltd. [source]

Ground thermal conditions in a frost-crack polygon, a palsa and a mineral palsa (lithalsa) in the discontinuous permafrost zone, northern Sweden

PERMAFROST AND PERIGLACIAL PROCESSES, Issue 4 2001
Bo Westin
Abstract Ground temperature measurements were collected during 1997 to 1998 at three locations in the discontinuous permafrost zone in northern Sweden. Measurements were made in two frost-crack polygons, two palsas and a mineral palsa (lithalsa). Important for the formation of permafrost at all locations are (i) the absence of snow and, (ii) local soil properties. The seasonal variation in apparent thermal diffusivity,with higher diffusivities in summer than in winter in the mineral soil of the frost-crack polygon and relatively little seasonal variation in the peat of the palsas,is the main cause for the cooler conditions in the palsas in summer. Morphology adds to the temperature fluctuations as indicated by highly fluctuating ground temperatures in the dome-shaped mineral palsa as compared to the frost-crack polygon. Occasional ground temperature gradients of more than ,10 °C/m are probably sufficient for seasonal frost cracking. Copyright © 2001 John Wiley & Sons, Ltd. RÉSUMÉ En trois endroits de la zone du pergélisol discontinu, Staloluokta, Kisuris, et Laivadalen dans le nord de la Suède où les températures moyennes annuelles sont d'environ,0.9°C, des mesures de température du sol ont été réalisées jusqu'à des profondeurs de 125 cm dans deux polygones de fissures de gel, deux palses et une palse minérale (lithalse). Le facteur le plus important pour la formation du pergélisol en tous les sites étudiés paraît être l'absence de couverture neigeuse et secondairement les propriétés des sols. Le pergélisol a été trouvé dans les sols des polygones de fissures de gel, dans les palses et la palse minérale, en des endroits où probablement une faible couverture de neige existe en hiver. La variation saisonnière de la diffusivité thermique apparente,avec une plus grande diffusivité en été qu'en hiver dans le sol minéral du polygone de fissure de gel et relativement peu de variations saisonnières dans la tourbe des palses,a été la cause principale des conditions plus froides dans la palse en hiver. La morphologie des formes périglaciaires peut engendrer des fluctuations de température plus importantes comme l'indique la grande variation de la température du sol dans une palse minérale en forme de dôme par comparaison avec ce qui se produit dans un polygone de fissures de gel de la même région. En outre, des gradients de température de plus de 10°C/m dans le sol gelé de la majeure partie des formes étudiées ont été probablement suffisants pour permettre la fissuration par contraction thermique. Copyright © 2001 John Wiley & Sons, Ltd. [source]

Genetic differences of rock glaciers and the discontinuous mountain permafrost zone in Kanchanjunga Himal, Eastern Nepal

PERMAFROST AND PERIGLACIAL PROCESSES, Issue 3 2001
Mamoru Ishikawa
Abstract A number of rock glaciers, including glacier-derived and talus-derived rock glaciers, were identified in Kanchanjunga Himal, easternmost Nepal. DC resistivity imagings were applied to representative rock glaciers of both types. The distribution of resistivity values in the subsurface within these rock glaciers was significantly different. A massive glacial ice body was found within the glacier-derived rock glacier, suggesting this rock glacier originated from glacial dead ice (ice-cored rock glacier). The lower limits of discontinuous mountain permafrost zone in Kanchanjunga Himal were inferred from the distribution of talus-derived rock glaciers (ice-cemented rock glaciers) and the estimated mean annual air temperature. The lower limit of the discontinuous mountain permafrost zone is 4800 m ASL on the north-facing slopes, while 5300 m ASL on the south- to east-facing slopes. These altitudes were considerably higher than those of the western Himalaya, which are under dry continental climatic conditions. Copyright © 2001 John Wiley & Sons, Ltd. RÉSUMÉ Plusieurs glaciers rocheux comprenant à la fois des formes dérivéees de vrais glaciers et des formes provenant de la mise en mouvement de talus, ont été identifiés dans le Kanchanjunga Himal, dans le Népal le plus oriental. Des images par résistivité DC ont été obtenues pour des glaciers représentatifs des deux catégories. La distribution des valeurs de résistivité en profondeur dans ces glaciers rocheux a été significativement différente. Un corps de glace massif a été trouvé dans le glacier rocheux provenant d'un vrai glacier suggérant qu'il s'agissait de glace morte glaciaire (glacier rocheux à noyau de glace). Les limites inférieures de la zone du pergélisol discontinu dans le Kanchanjungga Himal ont été déduites de la distribution des glaciers rocheux provenant de talus (glaciers rocheux avec de la glace ciment) et d'une estimation de la température moyenne annuelle de l'air. La limite inférieure de la zone du pergélisol discontinu de montagne est de 4800 m d'altitude sur les pentes exposées au nord, tandis que la limite est de 5300 m sur les pentes exposées au sud. Ces altitudes sont considérablement plus élevées que celles de l'ouest de l'Himalaya exposé à des conditions climatiques continentales sèches. Copyright © 2001 John Wiley & Sons, Ltd. [source]

Gas Hydrates in the Qilian Mountain Permafrost, Qinghai, Northwest China

ACTA GEOLOGICA SINICA (ENGLISH EDITION), Issue 1 2010
Youhai ZHU
Abstract: Qilian Mountain permafrost, with area about 10×104 km2, locates in the north of Qinghai-Tibet plateau. It equips with perfect conditions and has great prospecting potential for gas hydrate. The Scientific Drilling Project of Gas Hydrate in Qilian Mountain permafrost, which locates in Juhugeng of Muri Coalfield, Tianjun County, Qinghai Province, has been implemented by China Geological Survey in 2008,2009. Four scientific drilling wells have been completed with a total footage of 2059.13 m. Samples of gas hydrate are collected separately from holes DK-1, DK-2 and DK-3. Gas hydrate is hosted under permafrost zone in the 133,396 m interval. The sample is white crystal and easily burning. Anomaly low temperature has been identified by the infrared camera. The gas hydrate-bearing cores strongly bubble in the water. Gas-bubble and water-drop are emitted from the hydrate-bearing cores and then characteristic of honeycombed structure is left The typical spectrum curve of gas hydrate is detected using Raman spectrometry. Furthermore, the logging profile also indicates high electrical resistivity and sonic velocity. Gas hydrate in Qilian Mountain is characterized by a thinner permafrost zone, shallower buried depth, more complex gas component and coal-bed methane origin etc. [source]

Modeling past and future alpine permafrost distribution in the Colorado Front Range

EARTH SURFACE PROCESSES AND LANDFORMS, Issue 12 2005
Jason R. Janke
Abstract Rock glaciers, a feature associated with at least discontinuous permafrost, provide important topoclimatic information. Active and inactive rock glaciers can be used to model current permafrost distribution. Relict rock glacier locations provide paleoclimatic information to infer past conditions. Future warmer climates could cause permafrost zones to shrink and initiate slope instability hazards such as debris flows or rockslides, thus modeling change remains imperative. This research examines potential past and future permafrost distribution in the Colorado Front Range by calibrating an existing permafrost model using a standard adiabatic rate for mountains (0·5 °C per 100 m) for a 4 °C range of cooler and warmer temperatures. According to the model, permafrost currently covers about 12 per cent (326·1 km2) of the entire study area (2721·5 km2). In a 4 °C cooler climate 73·7 per cent (2004·4 km2) of the study area could be covered by permafrost, whereas in a 4°C warmer climate almost no permafrost would be found. Permafrost would be reduced severely by 93·9 per cent (a loss of 306·2 km2) in a 2·0 °C warmer climate; however, permafrost will likely respond slowly to change. Relict rock glacier distribution indicates that mean annual air temperature (MAAT) was once at least some 3·0 to 4·0 °C cooler during the Pleistocene, with permafrost extending some 600,700 m lower than today. The model is effective at identifying temperature sensitive areas for future monitoring; however, other feedback mechanisms such as precipitation are neglected. Copyright © 2005 John Wiley & Sons, Ltd. [source]

The lower limit of mountain permafrost in the Russian Altai Mountains

PERMAFROST AND PERIGLACIAL PROCESSES, Issue 2 2007
Kotaro Fukui
Abstract Permafrost-indicator features, such as rock glaciers, pingos and ice-wedge polygons, exist at many locations in and around the South Chuyskiy Range of the Russian Altai Mountains (,50°N). The distribution of these features suggests that the altitudinal range of the sporadic/patchy permafrost zones and the widespread discontinuous/continuous permafrost zones are 1800,2000,m ASL and above 2000,m ASL, respectively. The lower limit of discontinuous permafrost is approximately 200,m lower than in the Mongolian Altai, which are at a similar latitude. Cold air drainage and/or temperature inversions during winter within U-shaped valleys together with a thin snow cover because of low precipitation during the same season likely cause the lower permafrost limit in the study area. The calibrated 14C ages of tree remnants found in a rock glacier front in the lower Akkol valley were 293,±,21 years BP and 548,±,21 years BP. Given the time of emergence from beneath the Sofiyskiy glacier, this rock glacier developed between 3800,2600 and 550 years BP. Copyright © 2007 John Wiley & Sons, Ltd. [source]