Thermal State Of Permafrost Research Articles

Thermal state of permafrost in Russia

AbstractThe results of the International Permafrost Association's International Polar Year Thermal State of Permafrost (TSP) project are presented based on field measurements from Russia during the IPY years (2007–09) and collected historical data. Most ground temperatures measured in existing and new boreholes show a substantial warming during the last 20 to 30 years. The magnitude of the warming varied with location, but was typically from 0.5°C to 2°C at the depth of zero annual amplitude. Thawing of Little Ice Age permafrost is ongoing at many locations. There are some indications that the late Holocene permafrost has begun to thaw at some undisturbed locations in northeastern Europe and northwest Siberia. Thawing of permafrost is most noticeable within the discontinuous permafrost domain. However, permafrost in Russia is also starting to thaw at some limited locations in the continuous permafrost zone. As a result, a northward displacement of the boundary between continuous and discontinuous permafrost zones was observed. This data set will serve as a baseline against which to measure changes of near‐surface permafrost temperatures and permafrost boundaries, to validate climate model scenarios, and for temperature reanalysis. Copyright © 2010 John Wiley & Sons, Ltd.

Thermal state of permafrost and active‐layer monitoring in the antarctic: Advances during the international polar year 2007–2009

AbstractResults obtained during the International Polar Year (IPY) on the thermal state of permafrost and the active layer in the Antarctic are presented, forming part of ANTPAS (‘Antarctic Permafrost and Soils’), which was one of the key projects developed by the International Permafrost Association and the Scientific Committee for Antarctic Research for the IPY. The number of boreholes for permafrost and active‐layer monitoring was increased from 21 to 73 during the IPY, while CALM‐S sites to monitor the active layer were increased from 18 to 28. Permafrost temperatures during the IPY were slightly below 0°C in the South Shetlands near sea‐level, showing that this area is near the climatic boundary of permafrost and has the highest sensitivity to climate change in the region. Permafrost temperatures were much lower in continental Antarctica: from the coast to the interior and with increasing elevation they ranged between −13.3°C and −18.6°C in Northern Victoria Land, from −17.4°C to −22.5°C in the McMurdo Dry Valleys, and down to −23.6°C at high elevation on Mount Fleming (Ross Island). Other monitored regions in continental Antarctica also showed cold permafrost: Queen Maud Land exhibited values down to −17.8°C on nunataks, while in Novolazarevskaya (Schirmacher Oasis) at 80 m a.s.l. the permafrost temperature was −8.3°C. The coastal stations of Molodeznaya at Enderby Land showed permafrost temperatures of −9.8°C, Larsemann Hills – Progress Station in the Vestfold Hills region – recorded −8.5°C, and Russkaya in Marie Byrd Land, −10.4°C. This snapshot obtained during the IPY shows that the range of ground temperatures in the Antarctic is greater than in the Arctic. Copyright © 2010 John Wiley & Sons, Ltd.

Thermal state of permafrost in North America: a contribution to the international polar year

AbstractA snapshot of the thermal state of permafrost in northern North America during the International Polar Year (IPY) was developed using ground temperature data collected from 350 boreholes. More than half these were established during IPY to enhance the network in sparsely monitored regions. The measurement sites span a diverse range of ecoclimatic and geological conditions across the continent and are at various elevations within the Cordillera. The ground temperatures within the discontinuous permafrost zone are generally above −3°C, and range down to −15°C in the continuous zone. Ground temperature envelopes vary according to substrate, with shallow depths of zero annual amplitude for peat and mineral soils, and much greater depths for bedrock. New monitoring sites in the mountains of southern and central Yukon suggest that permafrost may be limited in extent. In concert with regional air temperatures, permafrost has generally been warming across North America for the past several decades, as indicated by measurements from the western Arctic since the 1970s and from parts of eastern Canada since the early 1990s. The rates of ground warming have been variable, but are generally greater north of the treeline. Latent heat effects in the southern discontinuous zone dominate the permafrost thermal regime close to 0°C and allow permafrost to persist under a warming climate. Consequently, the spatial diversity of permafrost thermal conditions is decreasing over time. Copyright © 2010 Crown in the right of Canada and John Wiley & Sons, Ltd.

Thermal state of permafrost and active layer in Central Asia during the international polar year

AbstractPermafrost in Central Asian is present in the Qinghai–Tibet Plateau in China, the Tien Shan Mountain regions in China, Kazakhstan and Kyrgyzstan, the Pamirs in Tajikistan, and in Mongolia. Monitoring of the ground thermal regime in these regions over the past several decades has shown that the permafrost has been undergoing significant changes caused by climate warming and increasing human activities. During the International Polar Year, measured mean annual ground temperature (MAGT) at a depth of 6 m ranged from −3.2°C to 0.2°C on the Qinghai–Tibet Plateau and the active‐layer thickness (ALT) varied between 105 and 322 cm at different sites. Ground temperatures at the bottom of the active layer (TTOP) warmed on average by 0.06°C yr−1 over the past decade. In Mongolia, MAGT at 10–15 m depth increased by up to 0.02–0.03°C yr−1 in the Hovsgol Mountain region, but by 0.01–0.02°C yr−1 in the Hangai and Hentei Mountain regions. The increase in permafrost temperatures in the northern Tien Shan from 1974 to 2009 ranged from 0.3°C to 0.6°C. At present measured permafrost temperatures vary from −0.5°C to −0.1°C. The ALT increased from 3.2 to 4 m in the 1970s to a maximum of 5.2 m between 1995 and 2009. Copyright © 2010 John Wiley & Sons, Ltd.

The thermal state of permafrost in the nordic area during the international polar year 2007–2009

AbstractThis paper provides a snapshot of the permafrost thermal state in the Nordic area obtained during the International Polar Year (IPY) 2007–2009. Several intensive research campaigns were undertaken within a variety of projects in the Nordic countries to obtain this snapshot. We demonstrate for Scandinavia that both lowland permafrost in palsas and peat plateaus, and large areas of permafrost in the mountains are at temperatures close to 0°C, which makes them sensitive to climatic changes. In Svalbard and northeast Greenland, and also in the highest parts of the mountains in the rest of the Nordic area, the permafrost is somewhat colder, but still only a few degrees below the freezing point. The observations presented from the network of boreholes, more than half of which were established during the IPY, provide an important baseline to assess how future predicted climatic changes may affect the permafrost thermal state in the Nordic area. Time series of active‐layer thickness and permafrost temperature conditions in the Nordic area, which are generally only 10 years in length, show generally increasing active‐layer depths and rising permafrost temperatures. Copyright © 2010 John Wiley & Sons, Ltd.

Processes and modes of permafrost degradation on the Qinghai-Tibet Plateau

Climate warming must lead the mainly air temperature controlled permafrost to degrade. Based on the numerical simulation, the process of permafrost degradation can be divided into five stages, i.e., starting stage, temperature rising stage, zero geothermal gradient stage, talic layers stage, and disappearing stage, according to the shape of ground temperature profile. Permafrost on the Qinghai-Tibet Plateau (QTP) is generally considered a relic from late Pleistocene, and has been degenerating as a whole during Holocene. According to spatial-temporal compensation, the present thermal state discrepancy of permafrost in different areas on the QTP may correspond with their degradation stages. On the QTP, permafrost in the high and middle mountains belongs to temperature rising stage, the permafrost thermal state is transiting from late rising temperature stage to zero geothermal gradient stage that is distributed in the middle-low-mountains. Permafrost that is in a zero gradient stage mainly appears in the high plateau and valley, whereas the transition from zero gradient stage to talic layers stage of permafrost is located in the vicinity of the lower limit of permafrost, and permafrost is disappearing from margin of perennially frozen ground. There are two modes of perennially frozen ground thawing, thawing from top to bottom and thawing from bottom to top respectively. During the temperature rising stage, when the heat flux in the perennially frozen soil layer is less than that in the unfrozen soil underlying frozen soil layer, the geothermal flux is partly used to thaw the base of permafrost, and permafrost thaws from bottom to top. With the decrease of thermal gradient in the perennially frozen ground, the heat that is used to thaw permafrost base increases, and geothermal heat will be entirely consumed to thaw the base of permafrost until the temperature gradient reaches zero thermal gradient state. On the other hand, the disappearance of permafrost may be delayed by “thermal offset” and “seasonal offset” effects in the upper of permafrost layer. When ground surface temperature rises to the level that can counteract the thermal offset effect, heat accumulation in the active layer would start, and the thickness of the active layer increases until a talic layer to appear. This process can be intensified by the “seasonal anti-offset effect”.

Impact of permafrost change on the Qinghai-Tibet Railroad engineering

Permafrost along the Qinghai-Tibet Railroad produces the great change under the influence of climate change, such as the decreasing of permafrost table, the rising of permafrost temperatures, etc. Climate effect on permafrost is the long-term process. Engineering action makes rapidly permafrost the large extent change. On the basis of analyzing the permafrost change under the climate change and engineering action, the thermal regime and spatial distribution of permafrost are predicted for air temperature rising 1°C and 2 °C after 50 years in this paper. The results show that climate change results in the larger change for the thermal regime and spatial distribution of permafrost. Permafrost change will produce the great effect on the Qinghai-Tibet Railroad engineering, not only resulting in the decreasing of permafrost table beneath the roadbed, but also resulting in thawing settlement due to the thawing of ground ice near permafrost table. The idea of cooling roadbed and active protecting permafrost for the Qinghai-Tibet Railroad engineering could adjust and control the permafrost thermal state, some better methods are provided to ensure the engineering stability in the areas of warm permafrost and high ice content.

The circumpolar active layer monitoring (calm) program: Research designs and initial results1

The Circumpolar Active Layer Monitoring (CALM) program, designed to observe the response of the active layer and near‐surface permafrost to climate change, currently incorporates more than 100 sites involving 15 investigating countries in both hemispheres. In general, the active layer responds consistently to forcing by air temperature on an interannual basis. The relatively few long‐term data sets available from northern high‐latitude sites demonstrate substantial interannual and interdecadal fluctuations. Increased thaw penetration, thaw subsidence, and development of thermokarst are observed at some sites, indicating degradation of warmer permafrost. During the mid‐ to late‐1990s, sites in Alaska and northwestern Canada experienced maximum thaw depth in 1998 and a minimum in 2000; these values are consistent with the warmest and coolest summers. The CALM network is part of the World Meteorological Organization's (WMO) Global Terrestrial Network for Permafrost (GTN‐P). GTN‐P observations consist of both the active layer measurements and the permafrost thermal state measured in boreholes. The CALM program requires additional multi‐decadal observations. Sites in the Antarctic and elsewhere in the Southern Hemisphere are presently being added to the bipolar network.

Climatic warming and the degradation of warm permafrost

Permafrost—a widespread constituent of the terrestrial environment—by definition is dependent upon the ambient temperature for its existence and properties. Thus, it is very sensitive to climatic changes. Simple relations based upon conductive heat transfer, with thawing and geothermal heat flow, are presented to predict the transient effects of surface temperature increases on the thermal state of permafrost. The results indicate that, based on the usual global warming scenarios, relatively small amounts of permafrost will disappear within 50–100 years. This is specifically shown for the most thermally sensitive cases, that is, warm or relict permafrost. © 1996 John Wiley & Sons, Ltd.