Permafrost warming has the potential to amplify global climate change, because when frozen sediments thaw it unlocks soil organic carbon. Yet to date, no globally consistent assessment of permafrost temperature change has been compiled. Here we use a global data set of permafrost temperature time series from the Global Terrestrial Network for Permafrost to evaluate temperature change across permafrost regions for the period since the International Polar Year (2007–2009). During the reference decade between 2007 and 2016, ground temperature near the depth of zero annual amplitude in the continuous permafrost zone increased by 0.39 ± 0.15 °C. Over the same period, discontinuous permafrost warmed by 0.20 ± 0.10 °C. Permafrost in mountains warmed by 0.19 ± 0.05 °C and in Antarctica by 0.37 ± 0.10 °C. Globally, permafrost temperature increased by 0.29 ± 0.12 °C. The observed trend follows the Arctic amplification of air temperature increase in the Northern Hemisphere. In the discontinuous zone, however, ground warming occurred due to increased snow thickness while air temperature remained statistically unchanged.

A continuous time series of annual soil thaw records, extending from 1994 to 2009, is available for comparison with the records of thaw obtained from the Biocomplexity Experiment (BE) for the period 2006–2009. Discontinuous records of thaw at Barrow from wet tundra sites date back to the 1960s. Comparisons between the longer records with the BE observations reveal strong similarities. Records of permafrost temperature, reflecting changes in the annual surface energy exchange, are available from the 1950s for comparison with results from measurement programs begun in 2002. The long‐term systematic geocryological investigations at Barrow indicate an increase in permafrost temperature, especially during the last several years. The increase in near‐surface permafrost temperature is most pronounced in winter. Marked trends are not apparent in the active‐layer record, although subsidence measurements on the North Slope indicate that penetration into the ice‐rich layer at the top of permafrost has occurred over the past decade. Active‐layer thickness values from the 1960s are generally higher than those from the 1990s, and are very similar to those of the 2000s. Analysis of spatial active‐layer observations at representative locations demonstrates significant variations in active‐layer thickness between different landscape types, reflecting the influence of vegetation, substrate, microtopography, and, especially, soil moisture. Landscape‐specific differences exist in the response of active‐layer thickness to climatic forcing. These differences are attributable to the existence of localized controls related to combinations of surface and subsurface characteristics. The geocryological records at Barrow illustrate the importance and effectiveness of sustained, well organized monitoring efforts to document long‐term trends.

Abstract. The Global Terrestrial Network for Permafrost (GTN-P) provides the first dynamic database associated with the Thermal State of Permafrost (TSP) and the Circumpolar Active Layer Monitoring (CALM) programs, which extensively collect permafrost temperature and active layer thickness (ALT) data from Arctic, Antarctic and mountain permafrost regions. The purpose of GTN-P is to establish an early warning system for the consequences of climate change in permafrost regions and to provide standardized thermal permafrost data to global models. In this paper we introduce the GTN-P database and perform statistical analysis of the GTN-P metadata to identify and quantify the spatial gaps in the site distribution in relation to climate-effective environmental parameters. We describe the concept and structure of the data management system in regard to user operability, data transfer and data policy. We outline data sources and data processing including quality control strategies based on national correspondents. Assessment of the metadata and data quality reveals 63 % metadata completeness at active layer sites and 50 % metadata completeness for boreholes.Voronoi tessellation analysis on the spatial sample distribution of boreholes and active layer measurement sites quantifies the distribution inhomogeneity and provides a potential method to locate additional permafrost research sites by improving the representativeness of thermal monitoring across areas underlain by permafrost. The depth distribution of the boreholes reveals that 73 % are shallower than 25 m and 27 % are deeper, reaching a maximum of 1 km depth. Comparison of the GTN-P site distribution with permafrost zones, soil organic carbon contents and vegetation types exhibits different local to regional monitoring situations, which are illustrated with maps. Preferential slope orientation at the sites most likely causes a bias in the temperature monitoring and should be taken into account when using the data for global models. The distribution of GTN-P sites within zones of projected temperature change show a high representation of areas with smaller expected temperature rise but a lower number of sites within Arctic areas where climate models project extreme temperature increase.GTN-P metadata used in this paper are available at

[1] Observations in undisturbed terrain within some regions of the Arctic reveal limited correlation between increasing air temperature and the thickness of the seasonally thawed layer above ice-rich permafrost. Here we describe landscape-scale, thaw-induced subsidence lacking the topographic contrasts associated with thermokarst terrain. A high-resolution, 11 year record of temperature and vertical movement at the ground surface from contrasting physiographic regions of northern Alaska, obtained with differential global positioning systems technology, indicates that thaw of an ice-rich layer at the top of permafrost has produced decimeter-scale subsidence extending over the entire landscapes. Without specialized observation techniques the subsidence is not apparent to observers at the surface. This "isotropic thaw subsidence" explains the apparent stability of active layer thickness records from some landscapes of northern Alaska, despite warming near-surface air temperatures. Integrated over extensive regions, it may be responsible for thawing large volumes of carbon-rich substrate and could have negative impacts on infrastructure.

Degradation of permafrost damages infrastructure and can jeopardize the sustainable development of polar and high-altitude regions. Warming and thawing of ice-rich permafrost is related to several natural hazards, which can pose a serious threat to the integrity of constructions and the economy. In this Review, we explore the extent and costs of observed and predicted infrastructure damages, and methods to mitigate adverse consequences of permafrost degradation. We also present the diversity of permafrost hazards and problems associated with construction and development in permafrost areas.Finally, we highlight seven topics to support sustainable infrastructure in the future. The observed damages are substantial and cumulative problems of infrastructure can be exacerbated owing to the increasing human activity in permafrost areas and climate change.It has been estimated that from one-third to more than half of critical circumpolar infrastructure could be at risk by mid-century. Permafrost degradation-related infrastructure costs could rise to tens of billion US dollars by the second half of the century.To successfully manage with climate change effects in permafrost areas a better understanding is needed about which constructions are likely to be affected by permafrost degradation. Especially, mitigation measures are needed to secure existing infrastructure and future development projects. Key points• Operational infrastructure is critical for sustainable development of Arctic and highaltitude communities, but the integrity of constructions is jeopardized by degrading permafrost.• The extent of observed damages is substantial (up to tens of percentages of infrastructure elements) and is likely to increase with climate warming.• From one-third to more than 50% of fundamental circumpolar infrastructure is at risk by mid-century.• Engineering solutions to mitigate the effects of degrading permafrost exist but their economic cost is high at regional scales.• There is a need to quantify the economic impacts of climate change on infrastructure and occurrence of permafrost-related infrastructure failure across the permafrost areas.• Future development projects should conduct local-scale infrastructure risk assessments and apply mitigation measures to avoid detrimental effects on constructions, socioeconomic activities, and ecosystems in permafrost areas under rapidly changing climatic conditions.