The relationship between soil temperature and its variations with different types of land cover are critical to understanding the effects of climate warming on ecohydrological processes in frozen soil regions such as the Qinghai-Tibet Plateau (QTP) of China. Biological soil crusts (biocrusts), which cover approximately 40% of the open soil surface in frozen soil regions, exert great impacts on soil temperatures. However, little attention has been given to the potential effects of biocrusts on the temperature characteristics, dynamics and freezing duration of soil in frozen soil regions. To provide more insight into this issue, an automatic system was used to monitor soil temperatures and dynamics at depths of 5, 30, 50 and 100 cm beneath bare soil and two types of biocrustal soils (soils covered with two types of biocrusts) on the QTP of China. The results showed that biocrusts play an important role in controlling the dynamics of soil temperatures. Biocrusts cause a 0.6-1 degrees C decrease in the mean annual temperature of soils down to a depth of 100 cm. The extent of the decrease in soil temperature was dependent on biocrust type, and dark biocrust showed a greater reduction in soil temperature than light biocrust. In addition, reductions in soil temperatures of biocrusts mainly occurred in daytimes of the thawing period, and this prolonged the freezing duration in the top 100 cm by approximately 10-20 days. The results of this study indicate that biocrusts maintain lower temperatures in the thawing period and slow the thawing of frozen soil in the spring, which helps to maintain the stability of the frozen soil. This information may aid understanding of the function of biocrusts in the frozen soil regions under global warming conditions.

Subarctic permafrost peatlands cover extensive areas and store large amounts of soil organic carbon that can be remobilized as active layer deepening and thermokarst formation increase in a future warmer climate. Better knowledge of ground thermal variability within these ecosystems is important for understanding future landscape development and permafrost carbon feedbacks. In a peat plateau complex in Tavvavuoma, northern Sweden, ground temperatures and snow depth have been monitored in six different landscape units: on a peat plateau, in a depression within a peat plateau, along a peat plateau edge (close to a thermokarst lake), at a thermokarst lake shoreline, in a thermokarst lake and in a fen. Permafrost is present in all three peat plateau landscape units, and mean annual ground temperature (MAGT) in the central parts of the peat plateau is -0.3 degrees C at 2 m depth. In the three low-lying wetter or saturated landscape units (along the thermokarst lake shoreline, in the lake and the fen) taliks are present and MAGT at 1 m depth is 1.0-2.7 degrees C. Topographical differences between the elevated and low-lying units affect both local snow depth and soil moisture, and are important for ground thermal patterns in this landscape. Permafrost exists in landscape units with a shallow mean December-April snow depth (40 cm mostly result in absence of permafrost.

The characteristics of temperature dynamics in a solonetzic meadow-chernozemic soil of alas depression in Central Yakutia are described on the basis of long-term (2005-2014) stationary studies. Quick changes in weather conditions accompanied by changes in the soil temperature regime were observed during that period. Thus, the beginning of soil thawing in the spring shifted to earlier dates, and the beginning of soil freezing in the fall shifted to later dates. Temperature trends demonstrate an increase in the mean annual soil temperatures at all the depths. In total, the period of the frozen state of the soil became considerably shorter: in the middle-profile horizons, by 30-39 days. The obtained results attest to the high dynamism in temperature parameters of meadow soils in alas depressions of Central Yakutia under conditions of global climate changes.

The 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 degrees C to 2 degrees 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 (C) 2010 John Wiley & Sons, Ltd.

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 degrees C. A greater range in MAGT is present within the continuous permafrost zone, from above -1 degrees C at some locations to as low as -15 degrees 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 degrees 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 (C) 2010 John Wiley & Sons, Ltd.

A 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 degrees C, and range down to -15 degrees 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 degrees C and allow permafrost to persist under a warming climate. Consequently, the spatial diversity of permafrost thermal conditions is decreasing over time. Copyright (C) 2010 Crown in the right of Canada and John Wiley & Sons, Ltd.