scholarly journals Analysis of Permafrost Thermal Dynamics and Response to Climate Change in the CMIP5 Earth System Models

2013 ◽  
Vol 26 (6) ◽  
pp. 1877-1900 ◽  
Author(s):  
Charles D. Koven ◽  
William J. Riley ◽  
Alex Stern
Keyword(s):  
Soil Temperature ◽  
Layer Thickness ◽  
Active Layer ◽  
Air Temperature ◽  
High Latitude ◽  
Cmip5 Models ◽  
Active Layer Thickness ◽  
Thermal Dynamics ◽  
Wide Range ◽  
Soil Temperatures

Abstract The authors analyze global climate model predictions of soil temperature [from the Coupled Model Intercomparison Project phase 5 (CMIP5) database] to assess the models’ representation of current-climate soil thermal dynamics and their predictions of permafrost thaw during the twenty-first century. The authors compare the models’ predictions with observations of active layer thickness, air temperature, and soil temperature and with theoretically expected relationships between active layer thickness and air temperature annual mean- and seasonal-cycle amplitude. Models show a wide range of current permafrost areas, active layer statistics (cumulative distributions, correlations with mean annual air temperature, and amplitude of seasonal air temperature cycle), and ability to accurately model the coupling between soil and air temperatures at high latitudes. Many of the between-model differences can be traced to differences in the coupling between either near-surface air and shallow soil temperatures or shallow and deeper (1 m) soil temperatures, which in turn reflect differences in snow physics and soil hydrology. The models are compared with observational datasets to benchmark several aspects of the permafrost-relevant physics of the models. The CMIP5 models following multiple representative concentration pathways (RCP) show a wide range of predictions for permafrost loss: 2%–66% for RCP2.6, 15%–87% for RCP4.5, and 30%–99% for RCP8.5. Normalizing the amount of permafrost loss by the amount of high-latitude warming in the RCP4.5 scenario, the models predict an absolute loss of 1.6 ± 0.7 million km2 permafrost per 1°C high-latitude warming, or a fractional loss of 6%–29% °C−1.

scholarly journals Linking tundra vegetation, snow, soil temperature, and permafrost

2020 ◽  
Vol 17 (16) ◽  
pp. 4261-4279
Author(s):  
Inge Grünberg ◽  
Evan J. Wilcox ◽  
Simon Zwieback ◽  
Philip Marsh ◽  
Julia Boike
Keyword(s):  
Soil Temperature ◽  
Snow Cover ◽  
Layer Thickness ◽  
Active Layer ◽  
Vegetation Change ◽  
Vegetation Type ◽  
Spatial Scales ◽  
Active Layer Thickness ◽  
Vegetation Types ◽  
Thermal Dynamics

Abstract. Connections between vegetation and soil thermal dynamics are critical for estimating the vulnerability of permafrost to thaw with continued climate warming and vegetation changes. The interplay of complex biophysical processes results in a highly heterogeneous soil temperature distribution on small spatial scales. Moreover, the link between topsoil temperature and active layer thickness remains poorly constrained. Sixty-eight temperature loggers were installed at 1–3 cm depth to record the distribution of topsoil temperatures at the Trail Valley Creek study site in the northwestern Canadian Arctic. The measurements were distributed across six different vegetation types characteristic for this landscape. Two years of topsoil temperature data were analysed statistically to identify temporal and spatial characteristics and their relationship to vegetation, snow cover, and active layer thickness. The mean annual topsoil temperature varied between −3.7 and 0.1 ∘C within 0.5 km2. The observed variation can, to a large degree, be explained by variation in snow cover. Differences in snow depth are strongly related with vegetation type and show complex associations with late-summer thaw depth. While cold winter soil temperature is associated with deep active layers in the following summer for lichen and dwarf shrub tundra, we observed the opposite beneath tall shrubs and tussocks. In contrast to winter observations, summer topsoil temperature is similar below all vegetation types with an average summer topsoil temperature difference of less than 1 ∘C. Moreover, there is no significant relationship between summer soil temperature or cumulative positive degree days and active layer thickness. Altogether, our results demonstrate the high spatial variability of topsoil temperature and active layer thickness even within specific vegetation types. Given that vegetation type defines the direction of the relationship between topsoil temperature and active layer thickness in winter and summer, estimates of permafrost vulnerability based on remote sensing or model results will need to incorporate complex local feedback mechanisms of vegetation change and permafrost thaw.

Modelled (1990-2100) Variations in Active-Layer Thickness and Ice-Wedge Activity Near Salluit, Nunavik (Canada)

2020 ◽  
Author(s):  
Samuel Gagnon ◽  
Michel Allard
Keyword(s):  
Soil Temperature ◽  
Layer Thickness ◽  
Active Layer ◽  
Air Temperature ◽  
Climate Warming ◽  
Active Layer Thickness ◽  
The Past ◽  
Temperature Thresholds ◽  
Ice Wedge ◽  
Cooling Trend

<p>Between 2016 and 2018, Gagnon and Allard (2019) investigated the impact of climate change on winter ice-wedge (IW) cracking frequency and IW morphology. In this study, they revisited 16 sites in the Narsajuaq valley (Canada) that were extensively studied between 1989 and 1991. Climate warming only started around 1993 whence mean annual air temperatures started to rise from -10 °C then to about -6 °C nowadays. This gave the unique opportunity to observe and measure changes by directly comparing field data with data pre-dating a climate warming of known amplitude. They found that based on IW tops, the active layer reached depths that were 1.2 to 3.4 times deeper than in 1991, which led to the widespread degradation of IW in the valley. Whereas 94% of the IWs unearthed in 1991 showed multiple recent growth structures, only 13% of the IWs unearthed in 2017 still had such features.</p><p>However, about half of the IWs in 2017 had ice veins connecting them to the base of the active layer, an indication that the recent cooling trend (2010-now) in the region was enough to reactivate frost cracking and IW growth. This shows that the soil system can respond quickly to short-term climate variations. For this study, we aimed to determine how changes in surface temperatures affected active-layer thickness (ALT) and dynamics over the past 25 years in order to understand the timing and reaching times of ground temperature thresholds for soil cracking and IW degradation. We used TONE, a one-dimensional finite-element thermal model, to simulate ground temperatures over the past 25 years. A monthly mean air temperature from a reanalysis (1948-2016) was combined with data from a weather station about 9 km west of the study area (2002-2018) to simulate the soil temperature profiles of four typical soil types found in the valley: thick sandy peat cover, thick peat cover, thin sandy peat cover, and fluvial sands.</p><p>Our results show that ALT variations were predominantly controlled by changes in thawing season air temperature with regards to the previous year. As soon as 1998, the active layer had already reached the main stages of the IWs, i.e. the largest and oldest part composing the IWs, but it is only from 2006 that the main stages started melt until 2010, an exceptionally warm year. Based on soil temperature thresholds, our results show that IWs remained active until around 2006. This means that as the active layer deepened and caused IW tops degradation, freezing season temperatures were still cold enough to induce soil cracking and IW growth in width. After 2010, the cooling trend was enough to reactivate the IWs from as a soon as 2011. This study shows that prior to advanced degradation, IWs can melt substantively and remain active at the same time as long as freezing season temperatures are cold enough to induce soil contraction cracking. However, it is likely that pulse events such as ground collapse will cause positive feedbacks contributing to rapid IW degradation before the soil completely stops cracking.</p>

Permafrost and active layer research on James Ross Island: An overview

2019 ◽  
Vol 9 (1) ◽  
pp. 20-36 ◽  
Author(s):  
Filip Hrbáček ◽  
Daniel Nývlt ◽  
Kamil Láska ◽  
Michaela Kňažková ◽  
Barbora Kampová ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Layer Thickness ◽  
Active Layer ◽  
Air Temperature ◽  
Thermal Regime ◽  
Ground Temperature ◽  
Active Layer Thickness ◽  
Near Surface ◽  
James Ross Island ◽  
The Mean

This study summarizes the current state of the active layer and permafrost research on James Ross Island. The analysis of climate parameters covers the reference period 2011–2017. The mean annual air temperature at the AWS-JGM site was -6.9°C (ranged from -3.9°C to -8.2°C). The mean annual ground temperature at the depth of 5 cm was -5.5°C (ranged from -3.3°C to -6.7°C) and it also reached -5.6°C (ranged from -4.0 to -6.8°C) at the depth of 50 cm. The mean daily ground temperature at the depth of 5 cm correlated moderately up to strongly with the air temperature depending on the season of the year. Analysis of the snow effect on the ground thermal regime confirmed a low insulating effect of snow cover when snow thickness reached up to 50 cm. A thicker snow accumulation, reaching at least 70 cm, can develop around the hyaloclastite breccia boulders where a well pronounced insulation effect on the near-surface ground thermal regime was observed. The effect of lithology on the ground physical properties and the active layer thickness was also investigated. Laboratory analysis of ground thermal properties showed variation in thermal conductivity (0.3 to 0.9 W m-1 K-1). The thickest active layer (89 cm) was observed on the Berry Hill slopes site, where the lowest thawing degree days index (321 to 382°C·day) and the highest value of thermal conductivity (0.9 W m-1 K-1) was observed. The clearest influence of lithological conditions on active layer thickness was observed on the CALM-S grid. The site comprises a sandy Holocene marine terrace and muddy sand of the Whisky Bay Formation. Surveying using a manual probe, ground penetrating radar, and an electromagnetic conductivity meter clearly showed the effect of the lithological boundary on local variability of the active layer thickness.

Contrasting thermal responses of permafrost to winter warming events under different snow regimes in the subarctic

2021 ◽  
Author(s):  
Didac Pascual Descarrega ◽  
Margareta Johansson
Keyword(s):  
Layer Thickness ◽  
Active Layer ◽  
Snow Depth ◽  
Thermal Response ◽  
Winter Precipitation ◽  
The Arctic ◽  
Active Layer Thickness ◽  
Thermal Dynamics ◽  
Winter Warming

<p>Winter warming events (WWE) in the Swedish subarctic are abrupt and short-lasting (hours-to-days) events of positive air temperature that occur during wintertime, sometimes accompanied by rainfall (rain on snow; ROS). These events cause changes in snow properties, which affect the below-ground thermal regime that, in turn, controls a suite of ecosystem processes ranging from microbial activity to permafrost and vegetation dynamics. For instance, winter melting can cause ground warming due to the shortening of the snow cover season, or ground cooling as the reduced snow depth and the formation of refrozen layers of high thermal conductivity at the base of the snowpack facilitate the release of soil heat. Apart from these interacting processes, the overall impacts of WWE on ground temperatures may also depend on the timing of the events and the preceding snowpack characteristics. The frequency and intensity of these events in the Arctic, including the Swedish subarctic, has increased remarkably during the recent decades, and is expected to increase even further during the 21st Century. In addition, snow depth (not necessarily snow duration) is projected to increase in many parts of the Arctic, including the Swedish subarctic. In 2005, a manipulation experiment was set up on a lowland permafrost mire in the Swedish subarctic, to simulate projected future increases in winter precipitation. In this study, we analyse this 15-year record of ground temperature, active layer thickness, and meteorological variables, to evaluate the short- (days to weeks) and long-term (up to 1 year) impacts of WWE on the thermal dynamics of lowland permafrost, and provide new insights into the influence of the timing of WWE and the underlying snowpack conditions on the thermal response of permafrost. On the short-term, the thermal responses to WWE are faster and stronger in areas with a shallow snowpack (5-10 cm), although these responses are more persistent in areas with a thicker snowpack (>25 cm), especially after ROS events. On the long term, permafrost in areas with a thicker snowpack exhibit a more durable warming response to WWE that results in thicker active layers at the end of the season. On the contrary, we do not observe a correlation between WWE and end of season active layer thickness in areas with a shallow snowpack. </p>

Mapping patterns of distribution and modern conditions of permafrost landscapes in Yakutia

2020 ◽  
pp. 52-62
Author(s):  
A.A. Shestakova ◽  
Keyword(s):  
Layer Thickness ◽  
Active Layer ◽  
Anthropogenic Impacts ◽  
Active Layer Thickness ◽  
Thematic Maps ◽  
Digital Maps ◽  
Soil Temperatures ◽  
Ice Content ◽  
Cryogenic Processes ◽  
Modern Condition

Digital thematic maps of the modern condition of permafrost landscapes of Yakutia on a scale of 1:1 500 000 have been compiled. A quantitative analysis of the patterns of their spatial distribution was carried out, the differentiation of permafrost landscapes by geocryological characteristics was made, and the areas that are most vulnerable to modern climate change and anthropogenic impacts were identified. The analysis of a series of digital thematic maps of the modern condition of permafrost landscapes in Yakutia showed that 34% of the total territory is occupied by landscapes with soil temperatures from −2 to −4 °C, the least common high-temperature permafrost landscapes (from 0 to −2 °C) – about 4% of the territory. Landscapes with active layer thickness values of about 1 m are spread over 36% of the territory, which is the highest indicator. Insignificant territories (up to 3%) are occupied by landscapes with active layer thickness of up to 3 and 3,5 m. The most widespread landscapes are those with low-ice deposits (less than 0,2) – 38,7%, and landscapes with heavy-ice deposits (more than 0,4) occupy 31%. The most dangerous process is thermokarst, which occurs in the interalassic and slightly drained types of terrain. Key words: permafrost landscape, temperature of soils, ice content of deposits, cryogenic processes, digital maps, GIS model.

scholarly journals Permafrost thaw and ground settlement considering long-term climate impact in northern Alaska

2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Zhaohui Joey Yang ◽  
Kannon C. Lee ◽  
Haibo Liu
Keyword(s):  
Layer Thickness ◽  
Active Layer ◽  
Air Temperature ◽  
Climate Model ◽  
Ground Surface ◽  
Active Layer Thickness ◽  
Near Surface ◽  
Surface Conditions ◽  
Ice Content ◽  
Northern Alaska

AbstractAlaska’s North Slope is predicted to experience twice the warming expected globally. When summers are longer and winters are shortened, ground surface conditions in the Arctic are expected to change considerably. This is significant for Arctic Alaska, a region that supports surface infrastructure such as energy extraction and transport assets (pipelines), buildings, roadways, and bridges. Climatic change at the ground surface has been shown to impact soil layers beneath through the harmonic fluctuation of the active layer, and warmer air temperature can result in progressive permafrost thaw, leading to a deeper active layer. This study attempts to assess climate change based on the climate model data from the fifth phase of the Coupled Model Intercomparison Project and its impact on a permafrost environment in Northern Alaska. The predicted air temperature data are analyzed to evaluate how the freezing and thawing indices will change due to climate warming. A thermal model was developed that incorporated a ground surface condition defined by either undisturbed intact tundra or a gravel fill surface and applied climate model predicted air temperatures. Results indicate similar fluctuation in active layer thickness and values that fall within the range of minimum and maximum readings for the last quarter-century. It is found that the active layer thickness increases, with the amount depending on climate model predictions and ground surface conditions. These variations in active layer thickness are then analyzed by considering the near-surface frozen soil ice content. Analysis of results indicates that thaw strain is most significant in the near-surface layers, indicating that settlement would be concurrent with annual thaw penetration. Moreover, ice content is a major factor in the settlement prediction. This assessment methodology, after improvement, and the results can help enhance the resilience of the existing and future new infrastructure in a changing Arctic environment.

scholarly journals A multisite dataset of near-surface soil temperature, active-layer thickness, and soil and vegetation conditions measured in northwestern Canada, 2016-2017

2021 ◽  
Author(s):  
Y Zhang ◽  
R Touzi ◽  
W Feng ◽  
G Hong ◽  
T C Lantz ◽  
...  
Keyword(s):  
Layer Thickness ◽  
Active Layer ◽  
Land Use Planning ◽  
Surface Soil ◽  
Active Layer Thickness ◽  
Data Set ◽  
Near Surface ◽  
Soil Temperatures ◽  
Surface Soil Temperature ◽  
Boreal Landscape

Quantifying and understanding spatial variation in permafrost conditions at the landscape-scale is important for land use planning and assessing the impacts of permafrost thaw. This report documents detailed field data observed at 110 sites in two areas in northwestern Canada from 2016 to 2017. One area is a northern boreal landscape near Inuvik and the other is a tundra landscape near Tuktoyaktuk. The observations include near-surface soil temperatures (Tnss) at 107 sites, and active-layer thickness, soil and vegetation conditions at 110 sites. The data set includes the original Tnss records, the calculated daily, monthly, and annual averages of Tnss, soil and vegetation conditions at these sites, and photographs taken in the field. This data set will be useful for understanding the spatial heterogeneity of permafrost and validating modelling and mapping products.

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