Vegetation can strongly regulate permafrost degradation at its southern edge through changing surface freeze-thaw processes

2018 ◽  
Vol 252 ◽  
pp. 10-17 ◽  
Author(s):  
Weichao Guo ◽  
Hongyan Liu ◽  
Oleg A. Anenkhonov ◽  
Huailiang Shangguan ◽  
Denis V. Sandanov ◽  
...  
Keyword(s):  
Permafrost Degradation ◽  
Freeze Thaw

scholarly journals Southwest-facing slopes control the formation of debris-covered glaciers in the Bhutan Himalaya

2013 ◽  
Vol 7 (4) ◽  
pp. 1303-1314 ◽  
Author(s):  
H. Nagai ◽  
K. Fujita ◽  
T. Nuimura ◽  
A. Sakai
Keyword(s):  
Satellite Images ◽  
Important Variable ◽  
Permafrost Degradation ◽  
Freeze Thaw ◽  
The North ◽  
Covered Area ◽  
Debris Cover ◽  
Local Topography ◽  
Formation Conditions ◽  
Geographic Setting

Abstract. To understand the formation conditions of debris-covered glaciers, we examined the dimension and shape of debris-covered areas and potential debris-supply (PDS) slopes of 213 glaciers in the Bhutan Himalaya. This was undertaken using satellite images with 2.5 m spatial resolution for manual delineation of debris-covered areas and PDS slopes. The most significant correlation exists between surface area of southwest-facing PDS slopes and debris-covered area. This result suggests that the southwest-facing PDS slopes supply the largest quantity of debris mantle. The shape of debris-covered areas is also an important variable, quantitatively defined using a geometric index. Elongate or stripe-like debris-covered areas on north-flowing glaciers are common throughout the Bhutan Himalaya. In contrast, south-flowing glaciers have large ablation zones, entirely covered by debris. Our findings suggest that this difference is caused by effective diurnal freeze–thaw cycles rather than seasonal freeze–thaw cycles, permafrost degradation, or snow avalanches. In terms of geographic setting, local topography also contributes to glacier debris supply and the proportion of debris cover on the studied glaciers is suppressed by the arid Tibetan climate, whereas the north-to-south asymmetric topography of the Bhutan Himalaya has less influence on the proportion of debris cover.

scholarly journals InSAR time series analysis of seasonal surface displacement dynamics on the Tibetan Plateau

2019 ◽  
Author(s):  
Eike Reinosch ◽  
Johannes Buckel ◽  
Jie Dong ◽  
Markus Gerke ◽  
Jussi Baade ◽  
...  
Keyword(s):  
Time Series ◽  
Tibetan Plateau ◽  
Time Series Analysis ◽  
Surface Displacement ◽  
The Tibetan Plateau ◽  
Permafrost Degradation ◽  
Nam Co ◽  
Freeze Thaw ◽  
Series Analysis ◽  
Spatial Coverage

Abstract. Climate change and the associated rise in air temperature have affected the Tibetan Plateau to a significantly stronger degree than the global average over the past decades. This has caused deglaciation, permafrost degradation and increased precipitation, heavily changing the water balance of this region. Surface displacement processes are likely to change as the ground continues to warm up and as such it is vital to understand both seasonal and interannual processes dynamics. The Nam Co area is well suited to studying these processes via Interferometric Synthetic Aperture Radar (InSAR) time series analysis, due to its lack of higher vegetation and relatively thin snow cover. The short revisit time of the Sentinel-1 system further reduces the risk of temporal decorrelation, making it possible to produce surface displacement models with good spatial coverage. We created three different surface displacement models to study freeze-thaw processes, seasonal sliding and linear creep. Most slopes of the area are unstable, with velocities of 8 to 17 mm yr−1, and some landforms reach velocities of up to 18 cm yr−1. The monsoonal climate accelerates those movements during the summer months through high temperatures and heavy rainfall. The fastest moving landforms, some of which have been identified as rock glaciers, do not follow this seasonal pattern of accelerated velocity in summer, instead they follow a linear sliding pattern. It is unclear if this linearity is connected to the ice content in those landforms. Flat regions at Nam Co are mostly stable on a multiannual scale but some experience subsidence, which could be caused by permafrost degradation. We observe a very clear seasonal freeze-thaw cycle in the valleys, where thawing and subsequent freezing of the active layer cause a vertical oscillation of the ground of up to a few centimeters, especially near streams and other water bodies.

scholarly journals Freeze-thaw processes of active layer regulate soil respiration of alpine meadow in the permafrost region of the Qinghai-Tibet Plateau

2019 ◽  
Author(s):  
Junfeng Wang ◽  
Qingbai Wu ◽  
Ziqiang Yuan ◽  
Hojeong Kang
Keyword(s):  
Soil Respiration ◽  
Active Layer ◽  
Alpine Meadow ◽  
Water Status ◽  
Tibet Plateau ◽  
Permafrost Region ◽  
Permafrost Degradation ◽  
Freezing And Thawing ◽  
Freeze Thaw ◽  
Qinghai Tibet Plateau

Abstract. Freezing and thawing action of the active layer plays a significant role in soil respiration (Rs) in permafrost regions. However, little is known about how the freeze-thaw process regulates the Rs dynamics in different stages for the alpine meadow underlain by permafrost on the Qinghai-Tibet Plateau (QTP). We conducted continuous in-situ measurements of Rs and freeze-thaw process of the active layer at an alpine meadow site in the Beiluhe permafrost region of QTP to determine the regulatory mechanisms of the different freeze-thaw stages of the active layer on the Rs. We found that the freezing and thawing process of active layer modified the Rs dynamics differently in different freeze-thaw stages. The mean Rs ranged from 0.56 to 1.75 μmol/m2s across the stages, with the lowest value in the SW stage and highest value in the ST stage; and Q10 among the different freeze-thaw stages changed greatly, with maximum (4.9) in the WC stage and minimum (1.7) in the SW stage. Patterns of Rs among the ST, AF, WC, and SW stages differed, and the corresponding contribution percentages of cumulative Rs to annual total Rs were 61.54, 8.89, 18.35, and 11.2 %, respectively. Soil temperature (Ts) was the most important driver of Rs regardless of soil water status in all stages. Our results suggest that as the climate warming and permafrost degradation continue, great changes in freeze-thaw process patterns may trigger more Rs emissions from this ecosystem because of prolonged ST stage.

scholarly journals Soil respiration of alpine meadow is controlled by freeze–thaw processes of active layer in the permafrost region of the Qinghai–Tibet Plateau

2020 ◽  
Vol 14 (9) ◽  
pp. 2835-2848
Author(s):  
Junfeng Wang ◽  
Qingbai Wu ◽  
Ziqiang Yuan ◽  
Hojeong Kang
Keyword(s):  
Soil Respiration ◽  
Active Layer ◽  
Alpine Meadow ◽  
Tibet Plateau ◽  
Permafrost Region ◽  
Permafrost Degradation ◽  
Freeze Thaw ◽  
Thaw Cycle ◽  
Freeze Thaw Cycle ◽  
Qinghai Tibet Plateau

Abstract. Freezing and thawing action of the active layer plays a significant role in soil respiration (Rs) in permafrost regions. However, little is known about how the freeze–thaw processes affect the Rs dynamics in different stages of the alpine meadow underlain by permafrost in the Qinghai–Tibet Plateau (QTP). We conducted continuous in situ measurements of Rs and freeze–thaw processes of the active layer at an alpine meadow site in the Beiluhe permafrost region of the QTP and divided the freeze–thaw processes into four different stages in a complete freeze–thaw cycle, comprising the summer thawing (ST) stage, autumn freezing (AF) stage, winter cooling (WC) stage, and spring warming (SW) stage. We found that the freeze–thaw processes have various effects on the Rs dynamics in different freeze–thaw stages. The mean Rs ranged from 0.12 to 3.18 µmol m−2 s−1 across the stages, with the lowest value in WC and highest value in ST. Q10 among the different freeze–thaw stages changed greatly, with the maximum (4.91±0.35) in WC and minimum (0.33±0.21) in AF. Patterns of Rs among the ST, AF, WC, and SW stages differed, and the corresponding contribution percentages of cumulative Rs to total Rs of a complete freeze–thaw cycle (1692.98±51.43 g CO2 m−2) were 61.32±0.32 %, 8.89±0.18 %, 18.43±0.11 %, and 11.29±0.11 %, respectively. Soil temperature (Ts) was the most important driver of Rs regardless of soil water status in all stages. Our results suggest that as climate change and permafrost degradation continue, great changes in freeze–thaw process patterns may trigger more Rs emissions from this ecosystem because of a prolonged ST stage.

scholarly journals Southwest-facing slopes control the formation of debris-covered glaciers in the Bhutan Himalaya

2013 ◽  
Vol 7 (2) ◽  
pp. 1673-1705
Author(s):  
H. Nagai ◽  
K. Fujita ◽  
T. Nuimura ◽  
A. Sakai
Keyword(s):  
Satellite Images ◽  
Important Variable ◽  
Permafrost Degradation ◽  
Freeze Thaw ◽  
The North ◽  
Covered Area ◽  
Debris Cover ◽  
Local Topography ◽  
Formation Conditions ◽  
Geographic Setting

Abstract. To understand the formation conditions of debris-covered glaciers, we examined the dimension and shape of debris-covered areas and potential debris-supply (PDS) slopes of 208 glaciers in the Bhutan Himalaya. This was undertaken using satellite images with 2.5 m spatial resolution for manual delineation of debris-covered areas and PDS slopes. The most significant correlation exists between surface area of southwest-facing PDS slopes and debris-covered area. This result suggests that the southwest-facing PDS slopes supply the largest quantity of debris mantle. The shape of debris-covered areas is also an important variable quantitatively defined using a geometric index. Elongate or stripe-like debris-covered areas on north-flowing glaciers are common throughout the Bhutan Himalaya, associated with the small quantities of debris from north-facing PDS slopes. In contrast, south-flowing glaciers have large ablation zones, entirely covered by debris. Our findings suggest that this difference is caused by effective diurnal freeze–thaw cycles rather than seasonal freeze–thaw cycles, permafrost degradation, or snow avalanches. In terms of geographic setting, local topography also contributes to glacier debris supply and the proportion of debris cover on the studied glaciers is suppressed by the arid Tibetan climate, whereas the north-to-south asymmetric topography of the Bhutan Himalaya has less influence on the proportion of debris cover.

Impacts of Permafrost Mean Annual Ground Temperature and Ice Content on Thermal Regime of Pile Foundation of Qinghai-Tibet Power Transmission Line

2012 ◽  
Vol 610-613 ◽  
pp. 2832-2839 ◽  
Author(s):  
Guo Yu Li ◽  
Qi Hao Yu ◽  
Wei Ma ◽  
Yan Hu Mu
Keyword(s):  
Power Transmission ◽  
Power Transmission Line ◽  
Permafrost Degradation ◽  
Enhanced Heat Transfer ◽  
Freeze Thaw ◽  
Thaw Cycle ◽  
Concrete Pile ◽  
Freeze Thaw Cycle ◽  
Surface Disturbance ◽  
Ice Content

The ±400 kV Qinghai-Tibet Power Transmission Line (QTPTL) was officially operated in December of 2011 on the Qinghai-Tibet Plateau (QTP) in China, crossing 550-km-long permafrost and 438-km-long seasonally frozen ground regions. Some of tower foundations of the QTPTL were buried in permafrost. It faces potential challenges of freeze- and thaw-related geohazards induced by freeze-thaw cycle, active layer thickening and permafrost degradation, which are mainly caused by climate warming, surface disturbance, enhanced heat transfer of concrete pile. These geohazards has become the concerns for stability and integrity of the QTPTL. In this study, some numerical tests on the thermal interaction between pile and permafrost were carried out to investigate impacts of permafrost mean annual ground temperature (MAGT) and ice content of soils surrounding pile on active layer thickening, permafrost degradation and freeze-thaw cycle considering climate warming, surface disturbance and enhanced heat transfer of concrete pile. The research results and discussions are described, which will provide the basis for normal operation and option of countermeasures against thaw settlement and frost jacking of the QTPTL, and the reference for the similar permafrost engineering in cold regions

scholarly journals Development and analysis of a continuous record of global near-surface soil freeze/thaw patterns from AMSR-E and AMSR2 data

2016 ◽  
Author(s):  
Tongxi Hu ◽  
Tianjie Zhao ◽  
Jiancheng Shi ◽  
Tianxing Wang ◽  
Dabin Ji ◽  
...  
Keyword(s):  
Spatial Distribution ◽  
Surface Soil ◽  
Permafrost Degradation ◽  
Near Surface ◽  
High Northern Latitude ◽  
Freeze Thaw ◽  
Discontinuous Permafrost ◽  
Data Record ◽  
Frost Period

Abstract. Monitoring near-surface soil freeze/thaw patterns is becoming essential under the context of global changes as it is more sensitive to climatic fluctuation compared with subsurface thermal characteristics and its evolution could be an early warning of changes in near-surface permafrost. It requires continuous long term and stable data record for understanding hydrological, ecological and biogeochemical responses of permafrost to global climate change. AMSR2 (Advanced Microwave Scanning Radiometer 2) is designed as a successor of AMSR-E (Advanced Microwave Scanning Radiometer – Earth Observing System) to ensure continuity of such observation. In this study, a linear regression is used to inter-calibrate the AMSR-E and AMSR2 brightness temperatures. Then discriminant function algorithm is adopted to produce a long term freeze/thaw data record. It is compared with in situ air temperature measurements from both the temporal and spatial aspects. The results show that the accuracy is consistent between AMSR-E and AMSR2 with a value above 85 %, according to the result of spatial distribution accuracy. Analysis is conducted with this data record to explore the spatial distribution of frost days, its changing trend and the frost probability of each pixel on a specific date. The mean annual frost days of high northern latitude (HNL, > 45° N) zone is 214.2 ± 69.5 days and the trend of frost days indicates that the frost period is decreasing at a rate of −0.0065 day/month in 27 % of the domain which is defined by significance level of the F-test, and most of which are concentrated in the high latitude area specifically over the Northeast of Canada, Central and Eastern Russia and most part of Eastern Europe. The significant changes in frost days mostly occur in regions of discontinuous permafrost and transient permafrost. The spatial distribution of the frost days and its trend variations are found to be consistent with the minimum temperature anomalies trend. It indicates that the global warming is not constant at different regions over the globe. Further analysis over the Qinghai-Tibetan Plateau where discontinuous permafrost, island permafrost, seasonally frozen ground exist demonstrated that the frost period is shortening slightly over the past decade, and the last frost date is advanced over more than half of the region. It is considered to be a remarkable indication for permafrost degradation in this area.

Soil Response during Globally Drained and Undrained Freeze–Thaw Cycles under Deviatoric Loading

2021 ◽  
Vol 147 (2) ◽  
pp. 06020030
Author(s):  
Sang Yeob Kim ◽  
Junghee Park ◽  
Wonjun Cha ◽  
Jong-Sub Lee ◽  
J. Carlos Santamarina
Keyword(s):  
Soil Response ◽  
Freeze Thaw
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