scholarly journals Spatio-Temporal Variations of Soil Active Layer Thickness in Chinese Boreal Forests from 2000 to 2015

2018 ◽  
Vol 10 (8) ◽  
pp. 1225 ◽  
Author(s):  
Xiongxiong Bai ◽  
Jian Yang ◽  
Bo Tao ◽  
Wei Ren
Keyword(s):  
Surface Temperature ◽  
Layer Thickness ◽  
Active Layer ◽  
Air Temperature ◽  
Climate Warming ◽  
Boreal Forests ◽  
Ground Surface ◽  
Active Layer Thickness ◽  
Ground Surface Temperature ◽  
Spatio Temporal

The soil active layer in boreal forests is sensitive to climate warming. Climate-induced changes in the active layer may greatly affect the global carbon budget and planetary climatic system by releasing large quantities of greenhouse gases that currently are stored in permafrost. Ground surface temperature is an immediate driver of active layer thickness (ALT) dynamics. In this study, we mapped ALT distribution in Chinese boreal larch forests from 2000 to 2015 by integrating remote sensing data with the Stefan equation. We then examined the changes of the ALT in response to changes in ground surface temperature and identified drivers of the spatio-temporal patterns of ALT. Active layer thickness varied from 1.18 to 1.3 m in the study area. Areas of nonforested land and low elevation or with increased air temperature had a relatively high ALT, whereas ALT was lower at relatively high elevation and with decreased air temperatures. Interannual variations of ALT had no obvious trend, however, and the ALT changed at a rate of only −0.01 and 0.01 m year−1. In a mega-fire patch of 79,000 ha burned in 2003, ΔALT (ALTi − ALT2002, where 2003 ≤ i ≤ 2015) was significantly higher than in the unburned area, with the influence of the wildfire persisting 10 years. Under the high emission scenario (RCP8.5), an increase of 2.6–4.8 °C in mean air temperature would increase ALT into 1.46–1.55 m by 2100, which in turn would produce a significant positive feedback to climate warming.

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.

Interactions between climate, vegetation and the active layer in soils at two Maritime Antarctic sites

2006 ◽  
Vol 18 (3) ◽  
pp. 323-333 ◽  
Author(s):  
N. Cannone ◽  
J.C. Ellis Evans ◽  
R. Strachan ◽  
M. Guglielmin
Keyword(s):  
Layer Thickness ◽  
Active Layer ◽  
Air Temperature ◽  
Vegetation Type ◽  
Ground Surface ◽  
Active Layer Thickness ◽  
Maritime Antarctic ◽  
Orkney Islands ◽  
Signy Island ◽  
Air Temperatures

In the summer 2000–01, thermal monitoring of the permafrost active layer within various terrestrial sites covered by lichen, moss or grasses was undertaken at Jubany (King George Island) and Signy Island in the Maritime Antarctic. The results demonstrated the buffering effect of vegetation on ground surface temperature (GST) and the relationship between vegetation and active layer thickness. Vegetation type and coverage influenced the GST in both locations with highest variations and values in the Deschampsia and Usnea sites and the lowest variations and values in the Jubany moss site. Active layer thickness ranged from 57 cm (Jubany moss site) to 227 cm (Signy Deschampsia site). Active layer thickness data from Signy were compared with data collected at the same location four decades earlier. Using a regression equation for air temperature versus ground surface temperatures the patterns of changing air temperature over time suggest that the active layer thickness increased c. 30 cm between 1963 and 1990 and then decreased 30 cm between 1990 and 2000. The documented increased rate of warming (2°C ± 1) since 1950 for air temperatures recorded in the South Orkney Islands suggests that the overall trend of active layer thickness increase will be around 1 cm year−1.

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.

scholarly journals A SPATIO-TEMPORAL FRAMEWORK FOR MODELING ACTIVE LAYER THICKNESS

2015 ◽  
Vol II-4/W2 ◽  
pp. 199-206
Author(s):  
J. Touyz ◽  
D. A. Streletskiy ◽  
F. E. Nelson ◽  
T. V. Apanasovich
Keyword(s):  
Layer Thickness ◽  
Active Layer ◽  
Environmental Changes ◽  
Predictive Accuracy ◽  
The Arctic ◽  
Active Layer Thickness ◽  
Error Statistics ◽  
Stochastic Component ◽  
Spatio Temporal ◽  
Naive Model

The Arctic is experiencing an unprecedented rate of environmental and climate change. The active layer (the uppermost layer of soil between the atmosphere and permafrost that freezes in winter and thaws in summer) is sensitive to both climatic and environmental changes, and plays an important role in the functioning, planning, and economic activities of Arctic human and natural ecosystems. This study develops a methodology for modeling and estimating spatial-temporal variations in active layer thickness (ALT) using data from several sites of the Circumpolar Active Layer Monitoring network, and demonstrates its use in spatial-temporal interpolation. The simplest model’s stochastic component exhibits no spatial or spatio-temporal dependency and is referred to as the naïve model, against which we evaluate the performance of the other models, which assume that the stochastic component exhibits either spatial or spatio-temporal dependency. The methods used to fit the models are then discussed, along with point forecasting. We compare the predicted fit of the various models at key study sites located in the North Slope of Alaska and demonstrate the advantages of space-time models through a series of error statistics such as mean squared error, mean absolute and percent deviance from observed data. We find the difference in performance between the spatio-temporal and remaining models is significant for all three error statistics. The best stochastic spatio-temporal model increases predictive accuracy, compared to the naïve model, of 33.3%, 36.2% and 32.5% on average across the three error metrics at the key sites for a one-year hold out period.

scholarly journals Permafrost Thaw and Ground Settlement Considering Long-Term Climate Impact in Northern Alaska

2021 ◽  
Author(s):  
Joey Yang ◽  
Kannon C. Lee ◽  
Haibo Liu
Keyword(s):  
Active Layer ◽  
Air Temperature ◽  
Climate Model ◽  
Ground Surface ◽  
North Slope ◽  
Active Layer Thickness ◽  
Near Surface ◽  
Surface Conditions ◽  
Air Temperatures ◽  
Ice Content

Abstract Alaska’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 infiltrate soil layers beneath through the harmonic fluctuation of the active layer. Past studies found that warmer air temperature resulted in increasingly deeper 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 study site on the North Slope. 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. It is found that the active layer thickens when the ground surface is either gravel fill or undisturbed tundra, but its thickness varies based on climate model predictions. These variations in active layer thickness are then analyzed by considering the near-surface frozen soil ice content. Analysis of results indicates that strain is most significant in the near-surface layers during thaw, indicating that settlement would be concurrent with annual thaw penetration. From this study, the climate model predicted air temperatures for a warming Arctic suggest that the thaw of near-surface frozen ground is largely dependent on ground surface conditions and the thermal properties of soil. Moreover, ice content is a major factor in the settlement predictions on Alaska’s North Slope. This study's results can help enhance the resilience of the existing and future new infrastructure in a changing Arctic environment.

scholarly journals Simulating Active Layer Thaw in a Boreal Environment

2007 ◽  
Vol 60 (1) ◽  
pp. 9-17 ◽  
Author(s):  
Ming-ko Woo ◽  
Michael Mollinga ◽  
Sharon L. Smith
Keyword(s):  
Surface Temperature ◽  
Phase Change ◽  
Active Layer ◽  
Oil And Gas ◽  
Environmental Changes ◽  
Ground Surface ◽  
Ground Surface Temperature ◽  
Annual Variations ◽  
Discontinuous Permafrost ◽  
Boreal Environment

Abstract A large part of the boreal zone of the western Canadian Arctic is underlain by ice-rich discontinuous permafrost which when thawed, can lead to settlement of the ground surface that has implications for the integrity of northern infrastructure, including oil and gas pipelines. A simple yet physically-based model is desired to simulate thawing of the active layer in different materials commonly found along the Mackenzie Valley pipeline corridor. Stefan’s algorithm determines the phase change of soil moisture using ground surface temperature as the upper boundary condition and conduction to transfer heat to the freeze-thaw front. It is tested on a permafrost site near Wrigley, Northwest Territories, where the computed thaw penetration compares satisfactorily with field data. To further explore the effects of climate and soil types on active layer depth, three representative sites in the Mackenzie valley where ground surface temperatures are available were selected for simulation of ground thaw, under two summer conditions. Results of the simulation demonstrate the sensitivity of active layer thaw to (1) soil materials due to differential thermal properties, (2) moisture content, which largely controls the latent heat requirement for phase change, and (3) inter-annual variations in ground surface temperature. Given the strong potential for environmental changes in the vast boreal region, the model allows the active layer thaw responses to be easily assessed.

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