Permafrost and Periglacial Processes 

About: Permafrost and Periglacial Processes is an academic journal published by Wiley-Blackwell. The journal publishes majorly in the area(s): Permafrost & Rock glacier. It has an ISSN identifier of 1045-6740. Over the lifetime, 1101 publications have been published receiving 46945 citations.

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

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.

Evidence for warming and thawing of discontinuous permafrost in Alaska

Abstract: Data show that permafrost temperatures along a north–south transect of Alaska from Old Man to Gulkana and at Healy generally warmed in the late 1980s to 1996. This trend was not followed at Eagle, about 330 km east of the transect. Estimates of the magnitude of the warming at the permafrost table ranged from 0.5°C to 1.5°C. Warming rates near the permafrost table were about 0.05 to 0.2°C a−1. No reliable trends in the depth of the base of ice-bearing permafrost or in the depth of the 0°C isotherm could be detected. Thermal offset allowed mean annual temperatures at the permafrost table to remain below 0°C with ground surface temperatures up to 2.5°C for a period of 8 years. The observed warming has probably caused discontinuous permafrost in marginal areas to begin thawing. Thawing permafrost and thermokarst have been observed at several sites. Thawing rates at the permafrost table at two sites were about 0.1 m a−1, indicating time scales of the order of a century to thaw the top 10 metres of ice-rich permafrost. Calculated thawing rates at the permafrost base are an order of magnitude smaller. Calibrated numerical models indicate that the permafrost warmed in the late 1960s and early 1970s in response to changes in air temperatures and snow covers. Additional warming in the late 1970s was caused by an increase in air temperatures beginning in 1977. Permafrost temperatures were nearly stable during the 1980s and then warmed again from the late 1980s to 1996, primarily in response to increased snow depths. This interpretation appears to be valid for all the sites in the region of the transect and at Healy. Copyright © 1999 John Wiley & Sons, Ltd. Des donnees montrent que les temperatures du pergelisol selon un transect Nord–Sud au travers de l'Alaska de Old Man jusqu'a Gulkana et a Healy se sont generalement elevees depuis la fin des annees 80 jusqu'a 1996. Cette tendance ne se retrouve pas a Eagle, environ 330 km a l'Est du transect. Des estimations de l'amplitude du rechauffement au niveau de la table du pergelisol varient de 0.5°C a 1.5°C. Les vitesses du rechauffement pres de la table du pergelisol ont ete d'environ 0.05 a 0.2°C par an. Aucune tendance certaine a la base du pergelisol riche en glace ou a la profondeur de l'isotherme de 0°C n'a pu etre detectee. La compensation thermique a permis de maintenir la table du pergelisol sous 0°C bien que les temperatures de surface aient ete superieures a 2.5°C pendant une periode de 8 ans. Le rechauffement observe a probablement cause un debut de fonte dans des regions marginales du pergelisol discontinu. Le degel du pergelisol ainsi que des phenomees thermokarstiques ont ete observes dans plusieurs sites. Les vitesses de degel a la table du pergelisol en deux sites ont ete de l'ordre d'environ 0.1 m par an, indiquant une echelle de temps de l'ordre de un siecle pour degeler les 10 m sommitaux de pergelisol riche en glace. Les vitesses de degel calculees pour la base du pergelisol sont un ordre de grandeur plus petit. Des modeles numeriques calibres indiquent que le pergelisol s'est rechauffe dans les dernieres annees 60 et au debut des annees 70 en reponse aux changements des temperatures de l'air et ceux de la couverture de neige. Un rechauffement supplementaire a la fin des annees 70 a ete cause par une augmentation de la temperature de l'air qui a debute en 1977. Les temperatures du pergelisol ont ete presque stables pendant les annees 1980 et se sont rechauffees de nouveau depuis la fin des annees 1980 jusqu'a 1996, principalement a la suite d'une augmentation de l'epaisseur de neige. Cette interpretation parait valable pour tous les sites dans la region du transect et a Healy. Copyright © 1999 John Wiley & Sons, Ltd.

Shrinking thermokarst ponds and groundwater dynamics in discontinuous permafrost near council, Alaska

Abstract: The purpose of this study was to characterize the geomorphological processes controlling the dynamics of ponds and to identify and characterize groundwater infiltration and surface water dynamics for a tundra terrain located in discontinuous permafrost near Council, Alaska. Thermokarst processes and permafrost degradation were studied, focusing upon the interaction between surface and groundwater systems via an open talik. Synthetic aperture radar (SAR) data were used for classification of terrain units and surface water properties, while historical aerial photographs and satellite images (IKONOS) were used for assessment of pond shrinking and recent thermokarst progression. Geophysical surveys (ground penetrating radar and DC resistivity) were conducted to detect permafrost thickness and talik formations. Temperature boreholes and hydrological observation wells were monitored throughout the year and provided ground truth for validation of remotely-sensed data and geophysical surveys. Field and laboratory analyses enabled quantitative determination of subsurface hydrologic and thermal properties. We found many areas where alluvium deposits and ice-wedge polygonal terrain had developed thermokarst features within the last 20 years. Thermokarst ponds located over ice-wedge terrain have decreased in surface area since at least the early 20th Century. Small thermokarst features initially developed into tundra ponds perched over permafrost in response to some local disturbance to the surface. These thermokarst ponds grew larger and initiated large taliks that completely penetrated the permafrost. These taliks allowed internal drainage throughout the year causing the ponds to shrink under recent climatic conditions. Shrinking pond surface areas may become a common feature in the discontinuous permafrost regions as a consequence of warming climate and thawing permafrost. Copyright © 2003 John Wiley & Sons, Ltd.

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

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.

Permafrost creep and rock glacier dynamics

Abstract: This review paper examines thermal conditions (active layer and permafrost), internal composition (rock and ice components), kinematics and rheology of creeping perennially frozen slopes in cold mountain areas. The aim is to assemble current information about creep in permafrost and rock glaciers from diverse published sources into a single paper that will be useful in studies of the flow and deformation of subsurface ice and their surface manifestations not only on Earth, but also on Mars. Emphasis is placed on quantitative information from drilling, borehole measurements, geophysical soundings, photogrammetry, laboratory experiments, etc. It is evident that quantitative holistic treatment of permafrost creep and rock glaciers requires consideration of: (a) rock weathering, snow avalanches and rockfall, with grain-size sorting on scree slopes; (b) freezing processes and ice formation in scree at sub-zero temperatures containing abundant fine material as well as coarse-grained blocks; (c) coupled thermohydro-mechanical aspects of creep and failure processes in frozen rock debris; (d) kinematics of non-isotropic, heterogeneous and layered, ice-rich permafrost on slopes with long transport paths for coarse surface material from the headwall to the front and, in some cases, subsequent re-incorporation into an advancing rock glacier causing corresponding age inversion at