The active layer thickness(ALT)in permafrost regions,which affects water and energy exchange,is a key variable for assessing hydrological processes,cold-region engineering,and climate change.In this study,the authors ...The active layer thickness(ALT)in permafrost regions,which affects water and energy exchange,is a key variable for assessing hydrological processes,cold-region engineering,and climate change.In this study,the authors analyzed the variation trends and relative changes of simulated ALTs using the Chinese Academy of Sciences Land Surface Model(CAS-LSM)and the Chinese Academy of Sciences Flexible Global Ocean-Atmosphere-Land System Model,gridpoint version 3(CAS-FGOALS-g3).Firstly,the simulated ALTs produced by CAS-LSM were shown to be reasonable by comparing them with Circumpolar Active Layer Monitoring observations.Then,the authors simulated the ALTs from 1979 to 2014,and their relative changes across the entire Northern Hemisphere from 2015 to 2100.It is shown that the ALTs have an increasing trend.From 1979 to 2014,the average ALTs and their variation trends over all permafrost regions were 1.08 m and 0.33 cm yr-1,respectively.The relative changes of the ALTs ranged from 1%to 58%,and the average relative change was 10.9%.The variation trends of the ALTs were basically consistent with the variation trends of the 2-m air temperature.By 2100,the relative changes of ALTs are predicted to be 10.3%,14.6%,30.1%,and 51%,respectively,under the four considered hypothetical climate scenarios(SSP-2.6,SSP2-4.5,SSP3-7.0,and SSP5-8.5).This study indicates that climate change has a substantial impact on ALTs,and our results can help in understanding the responses of the ALTs of permafrost due to climate change.展开更多
The active layer,acting as an intermediary of water and heat exchange between permafrost and atmosphere,greatly influences biogeochemical cycles in permafrost areas and is notably sensitive to climate fluctuations.Uti...The active layer,acting as an intermediary of water and heat exchange between permafrost and atmosphere,greatly influences biogeochemical cycles in permafrost areas and is notably sensitive to climate fluctuations.Utilizing the Chinese Meteorological Forcing Dataset to drive the Community Land Model,version 5.0,this study simulates the spatial and temporal characteristics of active layer thickness(ALT)on the Tibetan Plateau(TP)from 1980 to 2020.Results show that the ALT,primarily observed in the central and western parts of the TP where there are insufficient station observations,exhibits significant interdecadal changes after 2000.The average thickness on the TP decreases from 2.54 m during 1980–1999 to 2.28 m during 2000–2020.This change is mainly observed in the western permafrost region,displaying a sharp regional inconsistency compared to the eastern region.A persistent increasing trend of ALT is found in the eastern permafrost region,rather than an interdecadal change.The aforementioned changes in ALT are closely tied to the variations in the surrounding atmospheric environment,particularly air temperature.Additionally,the area of the active layer on the TP displays a profound interdecadal change around 2000,arising from the permafrost thawing and forming.It consistently decreases before 2000 but barely changes after 2000.The regional variation in the permafrost active layer over the TP revealed in this study indicates a complex response of the contemporary climate under global warming.展开更多
Active layer thickness（ALT） is critical to the understanding of the surface energy balance, hydrological cycles, plant growth, and cold region engineering projects in permafrost regions. The temperature at the botto...Active layer thickness（ALT） is critical to the understanding of the surface energy balance, hydrological cycles, plant growth, and cold region engineering projects in permafrost regions. The temperature at the bottom of the active layer, a boundary layer between the equilibrium thermal state（in permafrost below） and transient thermal state（in the atmosphere and surface canopies above）, is an important parameter to reflect the existence and thermal stability of permafrost. In this study, the Geophysical Institute Permafrost Model（GIPL） was used to model the spatial distribution of and changes in ALT and soil temperature in the Source Area of the Yellow River（SAYR）, where continuous, discontinuous, and sporadic permafrost coexists with seasonally frozen ground. Monthly air temperatures downscaled from the CRU TS3.0 datasets, monthly snow depth derived from the passive microwave remote-sensing data SMMR and SSM/I, and vegetation patterns and soil properties at scale of 1：1000000 were used as input data after modified with GIS techniques. The model validation was carried out carefully with in-situ ALT in the SAYR interpolated from the field-measured soil temperature data. The results of the model indicate that the average ALT in the SAYR has significantly increased from 1.8 m in 1980 to 2.4 m in 2006 at an average rate of 2.2 cm yr–1. The mean annual temperature at the bottom of the active layer, or temperature at the top of permafrost（TTOP） rose substantially from –1.1°C in 1980 to –0.6°C in 2006 at an average rate of 0.018°C yr–1. The increasing rate of the ALT and TTOP has accelerated since 2000. Regional warming and degradation of permafrost has also occurred, and the changes in the areal extent of regions with a sub-zero TTOP shrank from 2.4×104 to 2.2×104 km2 at an average rate of 74 km2 yr–1. Changes of ALT and temperature have adversely affected the environmental stability in the SAYR.展开更多
The soil freezing and thawing process affects soil physical properties,such as heat conductivity,heat capacity,and hydraulic conductivity in frozen ground regions,and further affects the processes of soil energy,hydro...The soil freezing and thawing process affects soil physical properties,such as heat conductivity,heat capacity,and hydraulic conductivity in frozen ground regions,and further affects the processes of soil energy,hydrology,and carbon and nitrogen cycles.In this study,the calculation of freezing and thawing front parameterization was implemented into the earth system model of the Chinese Academy of Sciences(CAS-ESM)and its land component,the Common Land Model(CoLM),to investigate the dynamic change of freezing and thawing fronts and their effects.Our results showed that the developed models could reproduce the soil freezing and thawing process and the dynamic change of freezing and thawing fronts.The regionally averaged value of active layer thickness in the permafrost regions was 1.92 m,and the regionally averaged trend value was 0.35 cm yr–1.The regionally averaged value of maximum freezing depth in the seasonally frozen ground regions was 2.15 m,and the regionally averaged trend value was–0.48 cm yr–1.The active layer thickness increased while the maximum freezing depth decreased year by year.These results contribute to a better understanding of the freezing and thawing cycle process.展开更多
Frozen ground degradation plays an important role in vegetation growth and activity in high-altitude cold regions.This study estimated the spatiotemporal variations in the active layer thickness(ALT)of the permafrost ...Frozen ground degradation plays an important role in vegetation growth and activity in high-altitude cold regions.This study estimated the spatiotemporal variations in the active layer thickness(ALT)of the permafrost region and the soil freeze depth(SFD)in the seasonally frozen ground region across the Three Rivers Source Region(TRSR)from 1980 to 2014 using the Stefan equation,and differentiated the effects of these variations on alpine vegetation in these two regions.The results showed that the average ALT from 1980 to 2014 increased by23.01 cm/10 a,while the average SFD decreased by 3.41 cm/10 a,and both changed intensively in the transitional zone between the seasonally frozen ground and permafrost.From 1982-2014,the increase in the normalized difference vegetation index(NDVI)and the advancement of the start of the vegetation growing season(SOS)in the seasonally frozen ground region(0.0078/10 a,1.83 d/10 a)were greater than those in the permafrost region(0.0057/10 a,0.39 d/10 a).The results of the correlation analysis indicated that increases in the ALT and decreases in the SFD in the TRSR could lead to increases in the NDVI and advancement of the SOS.Surface soil moisture played a critical role in vegetation growth in association with the increasing ALT and decreasing SFD.The NDVI for all vegetation types in the TRSR except for alpine vegetation showed an increasing trend that was significantly related to the SFD and ALT.During the study period,the general frozen ground conditions were favorable to vegetation growth,while the average contributions of ALT and SFD to the interannual variation in the NDVI were greater than that of precipitation but less than that of temperature.展开更多
In recent decades,research of the Alps,Qinghai-Tibet Plateau,and Cordillera have made great progress in understanding the phenomenon of permafrost.For the most part,this has been made possible due to temperature monit...In recent decades,research of the Alps,Qinghai-Tibet Plateau,and Cordillera have made great progress in understanding the phenomenon of permafrost.For the most part,this has been made possible due to temperature monitoring.However,the permafrost parameters in an area of more than 2 million square km of the mountainous regions of northeast Asia,for the most part,remain a blank spot in the scientific community.Due to the lack and insufficiency of factual materials,in 2012 the P.I.Melnikov Permafrost Institute began to take temperature measurements in the upper part of the permafrost in the central part of the VerkhoyanKolyma uplands,namely the Suntar-Khayat ridge.The article describes the temperature characteristics of air,surface and rocks of the active layer in the range of heights from 850 to 1821 m,in various landscape and topographic elements.For the observation period from 2012 to 2019,we obtained information on temperatures in the soils of the active layer at depths of 1 m,3 m,4 m,and 5 m and also air and surface temperature parameters.The availability of data on automated monitoring of rock temperatures in the active layer and the upper horizons of the layer of annual heat rotations made it possible to substantiate the most typical conditions of the temperature conditions of the permafrost zone of the characterized region.The parameters of permafrost existence and development are in favorable conditions.This is shown in the analysis of temperature data of air,surface and active layer.Soil temperatures in the active layer of annual heat rotations are most clearly represented at a depth of 1 m.Currently,on the territory of the mountain regions of Eastern Siberia,there are no more such sites for monitoring the temperature regime of soils.Information on the permafrost parameters in the region will allow us to begin the process of creating new models or checking existing forecasts and the distribution of the temperature pattern.It will also make it possible to evaluate the response of sensitive and vulnerable frozen soils of mountain regions to climate change.展开更多
Knowledge of the spatial distribution of permafrost and the effects of climate on ground temperature are important for land use and infrastructure development on the Qinghai-Tibet Plateau(QTP). Different permafrost mo...Knowledge of the spatial distribution of permafrost and the effects of climate on ground temperature are important for land use and infrastructure development on the Qinghai-Tibet Plateau(QTP). Different permafrost models have been developed to simulate the ground temperature and active layer thickness(ALT). In this study, Temperature at Top of Permafrost(TTOP) model, Kudryavtsev model and modified Stefan solution were evaluated against detailed field measurements at four distinct field sites in the Wudaoliang Basin to better understand the applicability of permafrost models. Field data from 2012 to 2014 showed that there were notable differences in observed ground temperatures and ALTs within and among the sites. The TTOP model is relatively simple, however, when driven by averaged input values, it produced more accurate permafrost surface temperature(Tps) than the Kudryavtsev model. The modified Stefan solution resulted in a satisfactory accuracy of 90%, which was better than the Kudryavtsev model for estimating ALTs. The modified Stefan solution had the potential of being applied to climate-change studies in the future. Furthermore, additional field investigations over longer periods focusing on hydrology, which has significant influence on permafrost thaw, are necessary. These efforts should employ advanced measurement techniques to obtain adequate and extensive local parameters that will help improve model accuracy.展开更多
The optimization of the drum structure is beneficial to improve the particle motion and mixing in rotary drums.In this work,two kinds of drum structures,Lacy cylinder drum(LC)and Lacy-lifters cylinder drum(LLC),are de...The optimization of the drum structure is beneficial to improve the particle motion and mixing in rotary drums.In this work,two kinds of drum structures,Lacy cylinder drum(LC)and Lacy-lifters cylinder drum(LLC),are developed on the basic of cylinder drum to enhance the heat transfer area.The particle motion and mixing process are simulated by DEM method.Based on the grid independence and model validation,the contact number between particles and wall,particle velocity profile,thickness of active layer,particle exchange coefficient,particle concentration profile and mixing index are demonstrated.The influences of the drum structure and the operation parameters are further evaluated.The results show that the contact number between particles and wall is improved in LC and LLC compared to cylinder drum.The particle velocity in LC is higher than that in cylinder drum at high rotating speed,and the particle velocity of the particle falling region is significantly improved in LLC.Compared to cylinder drum and LC,the thickness of active layer in LLC is smaller,while the local particle mixing quality is proved to be the best in the active region.In addition,the particle exchange coefficients between static region and active region in the three drums are compared and LLC is found tending to weaken the particle flow.Besides,the fluctuations of particle concentration in the active region,static region,and boundary region are weakened in LLC,and the equilibrium state is reached earlier.In addition,the overall particle mixing performance in cylinder drum,LC and LLC is analyzed.The particle mixing performance in cylinder drum is the worst,while the difference in mixing quality of LC and LLC depends on the operation conditions.展开更多
The Nanwenghe Wetlands Reserve in the Yile'huli Mountains is a representative region of the Xing'an permafrost.The response of permafrost to climate change remains unclear due to limited field investigations.T...The Nanwenghe Wetlands Reserve in the Yile'huli Mountains is a representative region of the Xing'an permafrost.The response of permafrost to climate change remains unclear due to limited field investigations.Thus,longer-term responses of the ground thermal state to climate change since 2011 have been monitored at four sites with varied surface characteristics:Carex tato wetland(P1)and shrub-C.tato wetland(P2)with a multi-year average temperatures at the depth of zero annual amplitude(T_(ZAA))of−0.52 and−1.19℃,respectively;Betula platyphylla-Larix gmelinii(Rupr.)Kuzen mixed forest(P3)with T_(ZAA) of 0.17℃,and;the forest of L.gmelinii(Rupr.)Kuzen(P4)with T_(ZAA) of 1.65℃.Continuous observations demonstrate that the ecosystem-protected Xing'an permafrost experienced a cooling under a warming climate.The temperature at the top of permafrost(TTOP)rose(1.8℃ per decade)but the TZAA declined(−0.14℃ per decade),while the active layer thickness(ALT)thinned from 0.9 m in 2012 to 0.8 m in 2014 at P1.Both the TTOP and TZAA increased(0.89 and 0.06℃ per decade,respectively),but the ALT thinned from 1.4 m in 2012 to 0.7 m in 2016 at P2.Vertically detached permafrost at P3 disappeared in summer 2012,with warming rates of+0.42 and+0.17℃ per decade for TTOP and T_(ZAA),respectively.However,up to date,the ground thermal state has remained stable at P4.We conclude that the thermal offset is crucial for the preservation and persistence of the Xing'an permafrost at the southern fringe.展开更多
The thermal state of frozen ground and its changes are important for understanding environmental change and supporting related applications to the Earth’s Third Pole,which is a hotspot area for science research.Howev...The thermal state of frozen ground and its changes are important for understanding environmental change and supporting related applications to the Earth’s Third Pole,which is a hotspot area for science research.However,challenges remain in data and modelling,meaning that much information is unavailable,especially for the entire Third Pole region.Here,we provided basic statistical data regarding the current state of frozen ground and its changes over the 1960s–2010s across the entire Third Pole by integrating nearly all currently available ground observation data and high-quality spatial data using machine learning models and existing high-quality frozen ground data products.The results show that the current(2000–2018)areal extents of permafrost and seasonally frozen ground in the Third Pole are approximately 1.27×10^(6)km^(2)(1.15×10^(6)to 1.39×10^(6)km^(2))and 2.59×10^(6)km^(2),accounting for 28%and 58%,respectively.The areal extent of permafrost region is approximately 50%(23%–93%)larger than that of permafrost area(land underlain by permafrost),especially in some early maps.The corresponding regional average of the mean annual ground temperature is approximately−1.51℃(−1.75 to−1.27℃)in the permafrost area.The regional average of active layer thickness overlying the permafrost and the maximum frost depth for regions of seasonally frozen ground are 235 cm(233–237 cm)and 92 cm,respectively.From the 1960s to the 2010s,on average,permafrost in the Third Pole warmed at a rate of 0.17℃per decade,which was associated with increases in the maximum thaw depth at a rate of 4.42 cm per decade.The regional average of the maximum frost depth declined at a rate of 2.34 cm per decade over the same period.This synthesis highlights the differences between the two terms(permafrost region and permafrost area)and provides crucial information for frozen ground in the Third Pole with higher accuracy for the scientific community and the public.展开更多
In boreal and arctic regions,forest fires exert great influences on biogeochemical processes,hydrothermal dynamics of the active layer and near-surface permafrost,and subsequent nutrient cycles.In this article,the stu...In boreal and arctic regions,forest fires exert great influences on biogeochemical processes,hydrothermal dynamics of the active layer and near-surface permafrost,and subsequent nutrient cycles.In this article,the studies on impacts of forest fires on the permafrost environment are reviewed.These studies indicate that forest fires could result in an irreversible degradation of permafrost,successions of boreal forests,rapid losses of soil carbon stock,and increased hazardous periglacial landforms.After forest fires,soil temperatures rise;active layer thickens;the release of soil carbon and nitrogen enhances,and;vegetation changes from coniferous forests to broad-leaved forests,shrublands or grasslands.It may take decades or even centuries for the fire-disturbed ecosystems and permafrost environment to return to pre-fire conditions,if ever possible.In boreal forest,the thickness of organic layer has a key influence on changes in permafrost and vegetation.In addition,climate warming,change of vegetation,shortening of fire return intervals,and extent of fire range and increasing of fire severity may all modify the change trajectory of the fire-impacted permafrost environment.However,the observations and research on the relationships and interactive mechanisms among the forest fires,vegetation,carbon cycle and permafrost under a changing climate are still inadequate for a systematic impact evaluation.Using the chronosequence approach of evaluating the temporal changes by measuring changes in the permafrost environment at different stages at various sites(possibly representing varied stages of permafrost degradation and modes),multi-source data assimilation and model predictions and simulations should be integrated with the results from long-and short-term field investigations,geophysical investigations and airborne surveys,laboratory testing and remote sensing.Future studies may enable quantitatively assess and predict the feed-back relationship and influence mechanism among organic layer,permafrost and active layer processes,vegetation and soil carbon under a warming climate at desired spatial and temporal scales.The irreversible changes in the boreal and artic forest ecosystem and their ecological and hydrothermal thresholds,such as those induced by forest fires,should be better and systematically studied.展开更多
基金supported by the National Key R&D Program of China[grant number 2018YFC1506602]the Key Research Program of Frontier Sciences,CAS[grant number QYZDY-SSW-DQC012]the National Natural Science Foundation of China[grant number 41830967]。
文摘The active layer thickness(ALT)in permafrost regions,which affects water and energy exchange,is a key variable for assessing hydrological processes,cold-region engineering,and climate change.In this study,the authors analyzed the variation trends and relative changes of simulated ALTs using the Chinese Academy of Sciences Land Surface Model(CAS-LSM)and the Chinese Academy of Sciences Flexible Global Ocean-Atmosphere-Land System Model,gridpoint version 3(CAS-FGOALS-g3).Firstly,the simulated ALTs produced by CAS-LSM were shown to be reasonable by comparing them with Circumpolar Active Layer Monitoring observations.Then,the authors simulated the ALTs from 1979 to 2014,and their relative changes across the entire Northern Hemisphere from 2015 to 2100.It is shown that the ALTs have an increasing trend.From 1979 to 2014,the average ALTs and their variation trends over all permafrost regions were 1.08 m and 0.33 cm yr-1,respectively.The relative changes of the ALTs ranged from 1%to 58%,and the average relative change was 10.9%.The variation trends of the ALTs were basically consistent with the variation trends of the 2-m air temperature.By 2100,the relative changes of ALTs are predicted to be 10.3%,14.6%,30.1%,and 51%,respectively,under the four considered hypothetical climate scenarios(SSP-2.6,SSP2-4.5,SSP3-7.0,and SSP5-8.5).This study indicates that climate change has a substantial impact on ALTs,and our results can help in understanding the responses of the ALTs of permafrost due to climate change.
基金supported by the Second Tibetan Plateau Scientific Expedition and Research(STEP)program[grant number 2019QZKK0102]the Youth Innovation Promotion Association CAS[grant number 2021073]the special fund of the Yunnan University“double firstclass”construction.
文摘The active layer,acting as an intermediary of water and heat exchange between permafrost and atmosphere,greatly influences biogeochemical cycles in permafrost areas and is notably sensitive to climate fluctuations.Utilizing the Chinese Meteorological Forcing Dataset to drive the Community Land Model,version 5.0,this study simulates the spatial and temporal characteristics of active layer thickness(ALT)on the Tibetan Plateau(TP)from 1980 to 2020.Results show that the ALT,primarily observed in the central and western parts of the TP where there are insufficient station observations,exhibits significant interdecadal changes after 2000.The average thickness on the TP decreases from 2.54 m during 1980–1999 to 2.28 m during 2000–2020.This change is mainly observed in the western permafrost region,displaying a sharp regional inconsistency compared to the eastern region.A persistent increasing trend of ALT is found in the eastern permafrost region,rather than an interdecadal change.The aforementioned changes in ALT are closely tied to the variations in the surrounding atmospheric environment,particularly air temperature.Additionally,the area of the active layer on the TP displays a profound interdecadal change around 2000,arising from the permafrost thawing and forming.It consistently decreases before 2000 but barely changes after 2000.The regional variation in the permafrost active layer over the TP revealed in this study indicates a complex response of the contemporary climate under global warming.
基金supported by the National Natural Science Foundation of China (Grant Nos. 41301068, 41121061)the State Key Laboratory of Frozen Soils Engineering (Grant No. Y252J41001,)the Foundation for Excellent Youth Scholars of CAREERI, CAS (Grant No. 51Y351051)
文摘Active layer thickness（ALT） is critical to the understanding of the surface energy balance, hydrological cycles, plant growth, and cold region engineering projects in permafrost regions. The temperature at the bottom of the active layer, a boundary layer between the equilibrium thermal state（in permafrost below） and transient thermal state（in the atmosphere and surface canopies above）, is an important parameter to reflect the existence and thermal stability of permafrost. In this study, the Geophysical Institute Permafrost Model（GIPL） was used to model the spatial distribution of and changes in ALT and soil temperature in the Source Area of the Yellow River（SAYR）, where continuous, discontinuous, and sporadic permafrost coexists with seasonally frozen ground. Monthly air temperatures downscaled from the CRU TS3.0 datasets, monthly snow depth derived from the passive microwave remote-sensing data SMMR and SSM/I, and vegetation patterns and soil properties at scale of 1：1000000 were used as input data after modified with GIS techniques. The model validation was carried out carefully with in-situ ALT in the SAYR interpolated from the field-measured soil temperature data. The results of the model indicate that the average ALT in the SAYR has significantly increased from 1.8 m in 1980 to 2.4 m in 2006 at an average rate of 2.2 cm yr–1. The mean annual temperature at the bottom of the active layer, or temperature at the top of permafrost（TTOP） rose substantially from –1.1°C in 1980 to –0.6°C in 2006 at an average rate of 0.018°C yr–1. The increasing rate of the ALT and TTOP has accelerated since 2000. Regional warming and degradation of permafrost has also occurred, and the changes in the areal extent of regions with a sub-zero TTOP shrank from 2.4×104 to 2.2×104 km2 at an average rate of 74 km2 yr–1. Changes of ALT and temperature have adversely affected the environmental stability in the SAYR.
基金This work was jointly funded by the National Natural Science Foundation of China(Grant Nos.42205168,41830967,and 42175163)the Youth Innovation Promotion Association CAS(2021073)the National Key Scientific and Technological Infrastructure project“Earth System Science Numerical Simulator Facility”(EarthLab).
文摘The soil freezing and thawing process affects soil physical properties,such as heat conductivity,heat capacity,and hydraulic conductivity in frozen ground regions,and further affects the processes of soil energy,hydrology,and carbon and nitrogen cycles.In this study,the calculation of freezing and thawing front parameterization was implemented into the earth system model of the Chinese Academy of Sciences(CAS-ESM)and its land component,the Common Land Model(CoLM),to investigate the dynamic change of freezing and thawing fronts and their effects.Our results showed that the developed models could reproduce the soil freezing and thawing process and the dynamic change of freezing and thawing fronts.The regionally averaged value of active layer thickness in the permafrost regions was 1.92 m,and the regionally averaged trend value was 0.35 cm yr–1.The regionally averaged value of maximum freezing depth in the seasonally frozen ground regions was 2.15 m,and the regionally averaged trend value was–0.48 cm yr–1.The active layer thickness increased while the maximum freezing depth decreased year by year.These results contribute to a better understanding of the freezing and thawing cycle process.
基金funded by the National Natural Science Foundation of China (41807061)Postdoctoral Science Foundation of China (2018M633454)+2 种基金Fundamental Research Funds for the Central Universities of China (GK201803046)National Science Foundation of China (41930641)National Key Research and Development Plan of China (2017YFC0504702)
文摘Frozen ground degradation plays an important role in vegetation growth and activity in high-altitude cold regions.This study estimated the spatiotemporal variations in the active layer thickness(ALT)of the permafrost region and the soil freeze depth(SFD)in the seasonally frozen ground region across the Three Rivers Source Region(TRSR)from 1980 to 2014 using the Stefan equation,and differentiated the effects of these variations on alpine vegetation in these two regions.The results showed that the average ALT from 1980 to 2014 increased by23.01 cm/10 a,while the average SFD decreased by 3.41 cm/10 a,and both changed intensively in the transitional zone between the seasonally frozen ground and permafrost.From 1982-2014,the increase in the normalized difference vegetation index(NDVI)and the advancement of the start of the vegetation growing season(SOS)in the seasonally frozen ground region(0.0078/10 a,1.83 d/10 a)were greater than those in the permafrost region(0.0057/10 a,0.39 d/10 a).The results of the correlation analysis indicated that increases in the ALT and decreases in the SFD in the TRSR could lead to increases in the NDVI and advancement of the SOS.Surface soil moisture played a critical role in vegetation growth in association with the increasing ALT and decreasing SFD.The NDVI for all vegetation types in the TRSR except for alpine vegetation showed an increasing trend that was significantly related to the SFD and ALT.During the study period,the general frozen ground conditions were favorable to vegetation growth,while the average contributions of ALT and SFD to the interannual variation in the NDVI were greater than that of precipitation but less than that of temperature.
基金supported by the Russian Science Fund under basic project No.IX.135.2“Geotemperature field and transformation of the permafrost zone of North Asia and mountainous regions of Central Asia”。
文摘In recent decades,research of the Alps,Qinghai-Tibet Plateau,and Cordillera have made great progress in understanding the phenomenon of permafrost.For the most part,this has been made possible due to temperature monitoring.However,the permafrost parameters in an area of more than 2 million square km of the mountainous regions of northeast Asia,for the most part,remain a blank spot in the scientific community.Due to the lack and insufficiency of factual materials,in 2012 the P.I.Melnikov Permafrost Institute began to take temperature measurements in the upper part of the permafrost in the central part of the VerkhoyanKolyma uplands,namely the Suntar-Khayat ridge.The article describes the temperature characteristics of air,surface and rocks of the active layer in the range of heights from 850 to 1821 m,in various landscape and topographic elements.For the observation period from 2012 to 2019,we obtained information on temperatures in the soils of the active layer at depths of 1 m,3 m,4 m,and 5 m and also air and surface temperature parameters.The availability of data on automated monitoring of rock temperatures in the active layer and the upper horizons of the layer of annual heat rotations made it possible to substantiate the most typical conditions of the temperature conditions of the permafrost zone of the characterized region.The parameters of permafrost existence and development are in favorable conditions.This is shown in the analysis of temperature data of air,surface and active layer.Soil temperatures in the active layer of annual heat rotations are most clearly represented at a depth of 1 m.Currently,on the territory of the mountain regions of Eastern Siberia,there are no more such sites for monitoring the temperature regime of soils.Information on the permafrost parameters in the region will allow us to begin the process of creating new models or checking existing forecasts and the distribution of the temperature pattern.It will also make it possible to evaluate the response of sensitive and vulnerable frozen soils of mountain regions to climate change.
基金funded by the State Key Development Program of Basic Research of China(973 Plan,Grant No.2012CB026101)the National Science and Technology Support Plan(Grant Nos.2014BAG05B01,2014BAG05B05)
文摘Knowledge of the spatial distribution of permafrost and the effects of climate on ground temperature are important for land use and infrastructure development on the Qinghai-Tibet Plateau(QTP). Different permafrost models have been developed to simulate the ground temperature and active layer thickness(ALT). In this study, Temperature at Top of Permafrost(TTOP) model, Kudryavtsev model and modified Stefan solution were evaluated against detailed field measurements at four distinct field sites in the Wudaoliang Basin to better understand the applicability of permafrost models. Field data from 2012 to 2014 showed that there were notable differences in observed ground temperatures and ALTs within and among the sites. The TTOP model is relatively simple, however, when driven by averaged input values, it produced more accurate permafrost surface temperature(Tps) than the Kudryavtsev model. The modified Stefan solution resulted in a satisfactory accuracy of 90%, which was better than the Kudryavtsev model for estimating ALTs. The modified Stefan solution had the potential of being applied to climate-change studies in the future. Furthermore, additional field investigations over longer periods focusing on hydrology, which has significant influence on permafrost thaw, are necessary. These efforts should employ advanced measurement techniques to obtain adequate and extensive local parameters that will help improve model accuracy.
文摘The optimization of the drum structure is beneficial to improve the particle motion and mixing in rotary drums.In this work,two kinds of drum structures,Lacy cylinder drum(LC)and Lacy-lifters cylinder drum(LLC),are developed on the basic of cylinder drum to enhance the heat transfer area.The particle motion and mixing process are simulated by DEM method.Based on the grid independence and model validation,the contact number between particles and wall,particle velocity profile,thickness of active layer,particle exchange coefficient,particle concentration profile and mixing index are demonstrated.The influences of the drum structure and the operation parameters are further evaluated.The results show that the contact number between particles and wall is improved in LC and LLC compared to cylinder drum.The particle velocity in LC is higher than that in cylinder drum at high rotating speed,and the particle velocity of the particle falling region is significantly improved in LLC.Compared to cylinder drum and LC,the thickness of active layer in LLC is smaller,while the local particle mixing quality is proved to be the best in the active region.In addition,the particle exchange coefficients between static region and active region in the three drums are compared and LLC is found tending to weaken the particle flow.Besides,the fluctuations of particle concentration in the active region,static region,and boundary region are weakened in LLC,and the equilibrium state is reached earlier.In addition,the overall particle mixing performance in cylinder drum,LC and LLC is analyzed.The particle mixing performance in cylinder drum is the worst,while the difference in mixing quality of LC and LLC depends on the operation conditions.
基金This study is financially supported by the program of National Natural Science Foundation of China(41401081,41871052,41771074)Joint Key Program of NSFC‒Heilongjiang Province for Regional Development(U20A2082)the Research Project of the State Key Laboratory of Frozen Soil Engineering(SKLFSE-ZT-41,SKLFSE-ZY-20).
文摘The Nanwenghe Wetlands Reserve in the Yile'huli Mountains is a representative region of the Xing'an permafrost.The response of permafrost to climate change remains unclear due to limited field investigations.Thus,longer-term responses of the ground thermal state to climate change since 2011 have been monitored at four sites with varied surface characteristics:Carex tato wetland(P1)and shrub-C.tato wetland(P2)with a multi-year average temperatures at the depth of zero annual amplitude(T_(ZAA))of−0.52 and−1.19℃,respectively;Betula platyphylla-Larix gmelinii(Rupr.)Kuzen mixed forest(P3)with T_(ZAA) of 0.17℃,and;the forest of L.gmelinii(Rupr.)Kuzen(P4)with T_(ZAA) of 1.65℃.Continuous observations demonstrate that the ecosystem-protected Xing'an permafrost experienced a cooling under a warming climate.The temperature at the top of permafrost(TTOP)rose(1.8℃ per decade)but the TZAA declined(−0.14℃ per decade),while the active layer thickness(ALT)thinned from 0.9 m in 2012 to 0.8 m in 2014 at P1.Both the TTOP and TZAA increased(0.89 and 0.06℃ per decade,respectively),but the ALT thinned from 1.4 m in 2012 to 0.7 m in 2016 at P2.Vertically detached permafrost at P3 disappeared in summer 2012,with warming rates of+0.42 and+0.17℃ per decade for TTOP and T_(ZAA),respectively.However,up to date,the ground thermal state has remained stable at P4.We conclude that the thermal offset is crucial for the preservation and persistence of the Xing'an permafrost at the southern fringe.
基金supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(XDA19070204)the National Natural Science Foundation of China(42071421).
文摘The thermal state of frozen ground and its changes are important for understanding environmental change and supporting related applications to the Earth’s Third Pole,which is a hotspot area for science research.However,challenges remain in data and modelling,meaning that much information is unavailable,especially for the entire Third Pole region.Here,we provided basic statistical data regarding the current state of frozen ground and its changes over the 1960s–2010s across the entire Third Pole by integrating nearly all currently available ground observation data and high-quality spatial data using machine learning models and existing high-quality frozen ground data products.The results show that the current(2000–2018)areal extents of permafrost and seasonally frozen ground in the Third Pole are approximately 1.27×10^(6)km^(2)(1.15×10^(6)to 1.39×10^(6)km^(2))and 2.59×10^(6)km^(2),accounting for 28%and 58%,respectively.The areal extent of permafrost region is approximately 50%(23%–93%)larger than that of permafrost area(land underlain by permafrost),especially in some early maps.The corresponding regional average of the mean annual ground temperature is approximately−1.51℃(−1.75 to−1.27℃)in the permafrost area.The regional average of active layer thickness overlying the permafrost and the maximum frost depth for regions of seasonally frozen ground are 235 cm(233–237 cm)and 92 cm,respectively.From the 1960s to the 2010s,on average,permafrost in the Third Pole warmed at a rate of 0.17℃per decade,which was associated with increases in the maximum thaw depth at a rate of 4.42 cm per decade.The regional average of the maximum frost depth declined at a rate of 2.34 cm per decade over the same period.This synthesis highlights the differences between the two terms(permafrost region and permafrost area)and provides crucial information for frozen ground in the Third Pole with higher accuracy for the scientific community and the public.
基金supported by the Natural Science Foundation of China Program(42001052)Startup Research Funding of Northeast Forest University for Chengdong Leadership(LJ2020-01)+3 种基金Outstanding Young Scholar(YQ2020-10)Natural Science Foundation of China Program(41871052),Joint Key Program of National Natural Science Foundation of China(NSFC)-Heilongjiang Province Joint Foundation for Regional Development(U20A2082)the State Key Laboratory of Frozen Soils Engineering Open Fund Project(SKLFSE201811)Russian Foundation for Basic Research(18-05-00990).
文摘In boreal and arctic regions,forest fires exert great influences on biogeochemical processes,hydrothermal dynamics of the active layer and near-surface permafrost,and subsequent nutrient cycles.In this article,the studies on impacts of forest fires on the permafrost environment are reviewed.These studies indicate that forest fires could result in an irreversible degradation of permafrost,successions of boreal forests,rapid losses of soil carbon stock,and increased hazardous periglacial landforms.After forest fires,soil temperatures rise;active layer thickens;the release of soil carbon and nitrogen enhances,and;vegetation changes from coniferous forests to broad-leaved forests,shrublands or grasslands.It may take decades or even centuries for the fire-disturbed ecosystems and permafrost environment to return to pre-fire conditions,if ever possible.In boreal forest,the thickness of organic layer has a key influence on changes in permafrost and vegetation.In addition,climate warming,change of vegetation,shortening of fire return intervals,and extent of fire range and increasing of fire severity may all modify the change trajectory of the fire-impacted permafrost environment.However,the observations and research on the relationships and interactive mechanisms among the forest fires,vegetation,carbon cycle and permafrost under a changing climate are still inadequate for a systematic impact evaluation.Using the chronosequence approach of evaluating the temporal changes by measuring changes in the permafrost environment at different stages at various sites(possibly representing varied stages of permafrost degradation and modes),multi-source data assimilation and model predictions and simulations should be integrated with the results from long-and short-term field investigations,geophysical investigations and airborne surveys,laboratory testing and remote sensing.Future studies may enable quantitatively assess and predict the feed-back relationship and influence mechanism among organic layer,permafrost and active layer processes,vegetation and soil carbon under a warming climate at desired spatial and temporal scales.The irreversible changes in the boreal and artic forest ecosystem and their ecological and hydrothermal thresholds,such as those induced by forest fires,should be better and systematically studied.
