Permafrost thaw subsidence, a key indicator of permafrost degradation, remains poorly quantified or understood. It is particularly challenging to detect and measure surface subsidence due to the loss ...of subsurface ice over a large area because it usually develops gradually, over several years or decades. Here we utilize the persistent scatterer interferometric synthetic aperture radar (PSI) approach to remotely measure gradual surface subsidence on Eboling Mountain in the northeastern region of the Qinghai‐Tibet Plateau, where thermal erosion gullies are well developed. Most of the previous multitemporal interferometric synthetic aperture radar studies on permafrost used the small baseline subset method. By contrast, the PSI approach benefits from the full spatial resolution and is less affected by temporal or geometric decorrelation. In the PSI analysis, we incorporate a piecewise elevation change model that includes periodic subsidence/uplift because of its seasonally varying components as well as its linear subsidence trends. Applying this permafrost‐designated PSI algorithm to 17‐L band ALOS‐1 PALSAR images taken between 2006 and 2011, we find that both the thermal erosion gullies and the surrounding regions (within about 300 m) subside gradually. The subsidence trends range from 0.3 to 3 cm/yr. This suggests that permafrost areas near the gullies are more vulnerable to gradual thawing and degradation. This study demonstrates the potential of using PSI to study permafrost thaw processes and of assessing its impacts over vast areas on the Qinghai‐Tibet Plateau and in the Arctic.
Key Points
Persistent scatterer interferometry is used to map gradual permafrost thaw subsidence with the full spatial resolution by exploiting all the repeat SAR acquisitions
A piecewise elevation change model is introduced to capture the dynamic processes of the active layer and the underlying permafrost
Ground surface subsidence, ranging from 0.3 to 3 cm/yr, occurred both inside the visible thermal erosion gullies and their surroundings
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Deep carbon pool in permafrost regions is an important component of the global terrestrial carbon cycle. However, the greenhouse gas production from deep permafrost soils is not well understood. ...Here, using soils collected from 5-m deep permafrost cores from meadow and wet meadow on the northern Qinghai-Tibetan Plateau (QTP), we investigated the effects of temperature on CO
and N
O production under aerobic incubations and CH
production under anaerobic incubations. After a 35-day incubation, the CO
N
O and CH
production at -2 °C to 10 °C were 0.44~2.12 mg C-CO
/g soil C, 0.0027~0.097 mg N-N
O/g soil N, and 0.14~5.88 μg C-CH
/g soil C, respectively. Greenhouse gas production in deep permafrost is related to the C:N ratio and stable isotopes of soil organic carbon (SOC), whereas depth plays a less important role. The temperature sensitivity (Q
) values of the CO
N
O and CH
production were 1.67-4.15, 3.26-5.60 and 5.22-10.85, without significant differences among different depths. These results indicated that climate warming likely has similar effects on gas production in deep permafrost and surface soils. Our results suggest that greenhouse gas emissions from both the deep permafrost and surface soils to the air will increase under future climate change.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
•TLS works effectively for studying thermokarst development.•High-resolution UAV images helps to identify thermokarst landforms including unstable margin.•Thermokarst develops to a larger extent ...during the thaw season starting from July.•The vertical deformation and headwall retreat of the thermokarst landforms presented consistency with ground temperature.•Extreme precipitation event triggered the severe deforming of the thermokarst landforms.
Climate warming has accelerated permafrost degradation over the Qinghai-Tibet Plateau (QTP) over the past several decades. The development of thermokarst landforms is a key indicator of permafrost degradation, while it lacks quantified measurements and comprehensive research over the QTP. The aim of this study is to investigate the development of thermokarst terrains through repeated ground-based elevation observations by using terrestrial laser scanning (TLS) in the northern QTP from April 11, 2016 through June 16, 2018. TLS Time series analysis reveals that the margin of the thermokarst landforms undergoes significant ground subsidence, side materials collapse, and/or uplift and deposit, especially in the southeastern, northwestern part of thermokarst landforms during the middle through the late thaw season. The vertical deformation and headwall retreat of thermokarst landforms reached −3.364 m and 10.66 m from April 11, 2016 to June 16, 2018, respectively. We also generated high-resolution orthophotos based on aerial photos acquired by the built-in 4 K RGB (red, green, blue) camera of DJI Phantom 3 Professional unmanned aerial vehicle (UAV) in April and October of 2016. The UAV images confirmed the TLS observations during the same period and presented the severely deformed area. This study reveals that the seasonal vertical deformation and headwall retreat of the thermokarst landforms in the study site are consistent with seasonal ground temperature change during the observed period. Extreme precipitation event as a key factor triggered the severe deforming of the case study thermokarst. Ground ice, peat layer, and human activity also contributed to the thermokarst landforms formation. The results also illustrate that TLS is an effective method for studying thermokarst development quantitatively.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Snow plays an important role in meteorological, hydrological and ecological processes, and snow phenology variation is critical for improved understanding of climate feedback on snow cover. The main ...purpose of the study is to explore spatial-temporal changes and variabilities of the extent, timing and duration, as well as phenology of seasonal snow cover across the large part of Eurasia from 2000 through 2016 using a Moderate Resolution Imaging Spectroradiometer (MODIS) cloud-free snow product produced in this study. The results indicate that there are no significant positive or negative interannual trends of snow cover extent (SCE) from 2000 to 2016, but there are large seasonal differences. SCE shows a significant negative trend in spring (p = 0.01) and a positive trend in winter. The stable snow cover areas accounting for 78.8% of the large part of Eurasia, are mainly located north of latitude 45° N and in the mountainous areas. In this stable area, the number of snow-covered days is significantly increasing (p < 0.05) in 6.4% of the region and decreasing in 9.1% of the region, with the decreasing areas being mainly located in high altitude mountain areas and the increasing area occurring mainly in the ephemeral snow cover areas of northeastern and southern China. In central Siberia, Pamir and the Tibetan Plateau, the snow onset date tends to be delayed while the end date is becoming earlier from 2000 to 2016. While in the relatively low altitude plain areas, such as the West Siberian Plain and the Eastern European Plain region, the snow onset date is tending to advance, the end date tends to be delayed, but the increase is not significant.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
The variability of soil carbon and nitrogen and the lack of information regarding the properties of deep soils in alpine permafrost regions hinder our understanding of ecosystem responses to climate ...change. The objective of this study was to examine the effects of pedogenesis and soil physicochemical parameters on the distributions of soil carbon and nitrogen and their characteristics of alpine meadows in permafrost regions. The results showed that pedogenesis was an important factor in the distribution of soil organic carbon (SOC) and total nitrogen (TN) in both the active layers and deep soils. The average water-soluble organic carbon (WSOC) content in the permafrost layer was higher than that of the active layer, which implied that the carbon pool in the permafrost layer was easily decomposable. Soil pH was an important factor that influenced soil inorganic carbon (SIC), which was closely associated with SOC in deep soils. The significant negative relationships between the SIC, pH and C/N ratios in permafrost regions implied that SIC can play an important role in the turnover of SOM and TN.
•We study the effects of pedogenesis and soil physicochemical parameter on carbon.•Labile carbon content in permafrost layer was higher than that in active layer.•SIC has an effect on distribution of organic carbon and nitrogen in deep layers.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Runoff estimation in high-altitude glacierized basins is an important issue on the Tibetan Plateau. To investigate glacier mass balance, runoff and water balance in the Qugaqie basin and Zhadang ...sub-basin in the southern Tibetan Plateau, two glacier models and three snow models were integrated into the spatially distributed hydrological model JAMS/J2K. The results showed that the temperature index method simulated glacier runoff better than the degree-day factor method. The simulated glacier melt volume in the Qugaqie basin in 2006, 2007 and 2008 contributed 58%, 50% and 41%, respectively, to its total runoff. In the Zhadang basin, the glacier melt volume contributed 78% and 66% to its runoff during 2007 and 2008, respectively. Compared with the observation results, the simulated glacier mass balance showed similar variations with slightly higher values, indicating an underestimation of glacier melt volume. The water balance simulation in the upstream areas (705–874 mm) was comparable to that in the downstream areas (1051–1502 mm) and generally lower than the observed results. In both basins, the glacier mass-balance simulation was relatively accurate in the melt season compared to the other seasons.
River ice thickness (RIT) directly influences human activities, such as rural transportation and subsistence activities, in addition to ecosystem and hydrology processes in the Arctic. Knowledge of ...RIT response to the rapid Arctic warming is very limited or essentially lacking. The scientific objective of this study is to investigate changes and variations in RIT and their response to rapid Arctic warming. We used ground-based measurements of 45 river gauge sites from 1961 through 2015 spanning 12 river basins across Alaska. The results indicate that the long-term mean maximum river ice thickness (MRIT) ranged from 40.3 ± 12.7 cm in the southeast to 187.3 ± 31.9 cm in northwest Alaska. MRIT decreased dramatically from 1961 to 2015, on average, at a rate of −0.26 ± 0.17 cm per year, and RIT declined significantly in all months from October through March, and more rapidly in winter than in autumn and spring. The impacts of air temperature and snowfall on MRIT change were analysed, and their relative influences were 74% and 26%, respectively. Specifically, an increase in air temperature was the primary factor contributing to MRIT decrease, while increasing snowfall, and snow on river ice enhanced MRIT decline. Seasonally, snowfall was the primary regulator for thickness change and higher air temperature resulted in RIT declining in autumn, while ice thickness decrease was mostly driven by warming in spring. However, neither air temperature nor snowfall is the primary control factor for declining RIT in winter, and further work needs to be done to detect the reason.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Land use and land cover change (LULCC) can alter surface climate through biogeophysical feedbacks including the modification of energy, moisture, and momentum exchanges between the land and ...atmosphere. Permafrost, a component of the cryosphere, plays an important role in the climate system. However, the role of permafrost in LULCC in cold regions is still not clearly understood. Here, we employ a LULCC sensitivity experiment carried out by the community Earth system model last millennium ensemble project to investigate the effect of LULCC in permafrost regions across the Northern Hemisphere during 850–2005. LULCC is associated with statistically significant large‐scale cooling in permafrost regions. The overall area‐averaged annual surface air temperature decreased 0.37°C during 850–2005, and soil temperature decreased 0.39°C. Active layer thickness declined at a rate of −0.54 cm/100 year ± 0.023 cm, with a net decline of 6.24 ± 0.26 cm during 850–2005 in association with LULCC. Soil moisture also showed a decrease, most pronounced in summer and autumn. Seasonally, the greatest surface air temperature decreases occurred in autumn at a rate of −0.042°C/100 year, and 0.2 m winter soil temperature decreased 0.036°C/100 year, both with time lags. Comparisons of cooling associated with LULCC demonstrate that permafrost regions are more sensitive to LULCC than the rest of the Northern Hemisphere.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
The degradation of mountain permafrost under climate warming may alter the runoff regime of high mountainous catchments. In this study, we evaluated the influence of permafrost on the hydrological ...regime using hydrological signals in the Yeniugou Basin located in a mountainous permafrost region in the Qilian Mountains of the northern Tibetan Plateau (TP). The effect of permafrost degradation on the hydrological response was assessed based on 28years of runoff and meteorological data. The results indicated that the investigated region exhibited a large increase in annual surface ground temperature from 1979 to 2006, with almost unchanged precipitation and evaporation potential. The winter runoff levels exhibited a significant decreasing linear trend, whereas the annual runoff and runoff in other seasons did not show any distinct linear trends. According to a comprehensive analysis of the relationships between winter runoff and meteorological factors, the ratio of maximum (Qmax) and minimum (Qmin) discharge, the recession coefficient and baseflow separation, and the reduced winter runoff were significantly correlated with thawing of permafrost. However, due to a time-lag response of climate forcing to permafrost thawing, some of these changes are undetectable over a short period. This study provides preliminary data on cold region hydrology and its response to climate change.
•Hydrological data are analyzed to determine the impact of permafrost degradation on hydrological regime.•Winter runoff is reduced in mountain permafrost regime of northern Tibetan Plateau.•Reduced winter runoff is mainly attributed to the permafrost thawing.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
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