The Experts below are selected from a list of 11706 Experts worldwide ranked by ideXlab platform
Dawen Yang - One of the best experts on this subject based on the ideXlab platform.
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spatiotemporal variations in Frozen Ground and their impacts on hydrological components in the source region of the yangtze river
Journal of Hydrology, 2020Co-Authors: Ruijie Shi, Hanbo Yang, Dawen YangAbstract:Abstract The source region of the Yangtze River (SRYR), located on the eastern Tibetan Plateau, is an essential part of the Asian Water Tower and plays an important role in the downstream water resources. Significant changes in Frozen Ground caused by increases in air temperature have been widely reported in the past several decades, which has greatly affected regional runoff. This study evaluated the spatiotemporal variations in Frozen Ground and hydrological components by utilizing a geomorphology-based eco-hydrological model (GBEHM) and investigated the reasons for runoff changes based on the Budyko framework. The results showed that the area with an elevation range of 4700–4800 m located in the permafrost region was the main source area of runoff generation from 1981 to 2015. Compared with the permafrost region, the seasonally Frozen Ground (SFG) region had a larger ratio of annual evapotranspiration to annual precipitation, although the aridity indices in the two regions were very similar. From 1981 to 2015, the mean value of the maximum Frozen depth of SFG (MFDSFG) decreased by 12.3 cm/10 a and the mean value of the active layer thickness (ALT) of permafrost increased by 4.2 cm/10 a. The annual runoff in the SFG region decreased, while that in the permafrost region increased. Runoff change was more sensitive to precipitation change in the higher altitude regions that were mainly covered by permafrost than in the lower altitude regions that were mainly covered by the SFG, while the evapotranspiration change in the transition zone was more sensitive to climate change. An abrupt change in the annual runoff time series was detected in 1989, 2004, and 2004 in the SFG region, the permafrost region and the entire SRYR, respectively, and the annual runoff change from period 1 (1981 to change point) to period 2 (change point + 1 to 2015) were −25.7 mm, 33.8 mm and 25.8 mm respectively. Frozen Ground degradation contributed changes of −15.0 mm, −8.8 mm and −11.6 mm to the annual runoff in the SFG region, the permafrost region and the entire SRYR, respectively. This result implied that Frozen Ground degradation had a negative impact on regional runoff in the SRYR. These findings deepen our understanding of Frozen Ground and its hydrological changes and are helpful for water resource management in the SRYR.
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data driven mapping of the spatial distribution and potential changes of Frozen Ground over the tibetan plateau
Science of The Total Environment, 2019Co-Authors: Taihua Wang, Dawen Yang, Yue Qin, Beijing Fang, Wencong Yang, Yuhan WangAbstract:Abstract Frozen Ground degradation profoundly impacts the hydrology, ecology and human society on the Tibetan Plateau (TP) and the downstream regions. The spatial distribution and potential changes of permafrost and maximum thickness of seasonally Frozen Ground (MTSFG) on the TP is of great importance and needs more in-depth studies. This study maps the permafrost and MTSFG distribution in the baseline period (2003−2010) and in the future (2040s and 2090s) with 1-km resolution. Logistic regression (LR), support vector machine (SVM) and random forest (RF) are validated using 106 borehole observations and proved to be applicable in estimating permafrost distribution. According to the majority voting results of the three algorithms, 45.9% area of the TP is underlain by permafrost in the baseline period, and respectively 25.9% and 43.9% of the current permafrost will disappear by the 2040s and the 2090s projected by mean of the projections from the five General Circulation Models under the Representative Concentration Pathway 4.5 scenario. SVM performs better in spatial generalization than RF based on the results of nested cross validation. According to the MTSFG results derived from SVM, the most dramatic decrease in MTSFG will occur in the southwestern TP, which is projected to exceed 50 cm in the 2090s compared with the baseline period. This study introduces the statistics and machine learning algorithms to Frozen Ground estimation on the TP, and the high resolution permafrost and MTSFG maps produced by this study can provide useful information for future studies on the third pole region.
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Frozen Ground degradation may reduce future runoff in the headwaters of an inland river on the northeastern tibetan plateau
Journal of Hydrology, 2018Co-Authors: Yuhan Wang, Bing Gao, Yue Qin, Taihua Wang, Hanbo Yang, Dawen YangAbstract:Abstract On the Tibetan Plateau, climate change, particularly increases in air temperature, significantly affects cryospheric and hydrological processes. Based on 5 typical future climate scenarios from the Coupled Model Intercomparison Project (CMIP5) under emission scenario RCP4.5 and a distributed ecohydrological model (GBEHM), this study analyzes the potential characteristics of future climate change (from 2011 to 2060) and the associated effects on the cryospheric and hydrological processes in the upper Heihe River Basin, a typical cold mountain region located on the northeastern Tibetan Plateau. The precipitation, air temperature, and Frozen Ground elasticities of runoff/evapotranspiration are then estimated based on the simulation results. The typical future climate scenarios suggest that air temperature will increase at an average rate of 0.34 °C/10a in the future and that precipitation will increase slightly by 6 mm/10a under the RCP 4.5 emission scenario. Based on the GBEHM-simulated results, due to the increase in air temperature, glaciers would be reduced to less than 100 million m3 by 2060, the permafrost area would shrink by 23%, the maximum Frozen depth of seasonally Frozen Ground would decrease by 5.4 cm/10a and the active layer depth of the Frozen Ground would increase by 6.1 cm/10a. Additionally, runoff would decrease by approximately 5 mm/10a, and evapotranspiration would increase by approximately 9 mm/10a. The estimated elasticities indicate that annual runoff would decrease at an average rate of 24 mm/°C and evapotranspiration would increase at an average rate of 21 mm/°C with rising air temperature in the future. The impacts of increased air temperature on hydrological processes are mainly due to changes in Frozen Ground. The thickening of the active layer of the Frozen Ground increases the soil storage capacity, leading to decreased runoff and increased evapotranspiration. When the active layer depth increases by 1 cm, annual runoff decreases by approximately 1.3 mm, and annual evapotranspiration increases by approximately 0.9 mm. In addition, the shift from permafrost to seasonal Frozen Ground increases Groundwater infiltration, which decreases surface runoff. Compared to that over the past 50 years, the effect of increased air temperature on the Frozen Ground in the upper Heihe River Basin will be greater in the future, which would result in a faster reduction in runoff in the future considering the effects of global warming.
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historical and future changes of Frozen Ground in the upper yellow river basin
Grid and Pervasive Computing, 2018Co-Authors: Taihua Wang, Dawen Yang, Bing Gao, Yue Qin, Yuhan Wang, Yun Chen, Hanbo YangAbstract:Abstract Frozen Ground degradation resulting from climate warming on the Tibetan Plateau has aroused wide concern in recent years. In this study, the maximum thickness of seasonally Frozen Ground (MTSFG) is estimated by the Stefan equation, which is validated using long-term Frozen depth observations. The permafrost distribution is estimated by the temperature at the top of permafrost (TTOP) model, which is validated using borehole observations. The two models are applied to the upper Yellow River Basin (UYRB) for analyzing the spatio-temporal changes in Frozen Ground. The simulated results show that the areal mean MTSFG in the UYRB decreased by 3.47 cm/10 a during 1965–2014, and that approximately 23% of the permafrost in the UYRB degraded to seasonally Frozen Ground during the past 50 years. Using the climate data simulated by 5 General Circulation Models (GCMs) under the Representative Concentration Pathway (RCP) 4.5, the areal mean MTSFG is projected to decrease by 1.69 to 3.07 cm/10 a during 2015–2050, and approximately 40% of the permafrost in 1991–2010 is projected to degrade into seasonally Frozen Ground in 2031–2050. This study provides a framework to estimate the long-term changes in Frozen Ground based on a combination of multi-source observations at the basin scale, and this framework can be applied to other areas of the Tibetan Plateau. The estimates of Frozen Ground changes could provide a scientific basis for water resource management and ecological protection under the projected future climate changes in headwater regions on the Tibetan Plateau.
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quantifying the streamflow response to Frozen Ground degradation in the source region of the yellow river within the budyko framework
Journal of Hydrology, 2018Co-Authors: Taihua Wang, Dawen Yang, Yue Qin, Hanbo Yang, Yuhan WangAbstract:Abstract The source region of the Yellow River (SRYR) is greatly important for water resources throughout the entire Yellow River Basin. Streamflow in the SRYR has experienced great changes over the past few decades, which is closely related to the Frozen Ground degradation; however, the extent of this influence is still unclear. In this study, the air freezing index (DDFa) is selected as an indicator for the degree of Frozen Ground degradation. A water-energy balance equation within the Budyko framework is employed to quantify the streamflow response to the direct impact of climate change, which manifests as changes in the precipitation and potential evapotranspiration, as well as the impact of Frozen Ground degradation, which can be regarded as part of the indirect impact of climate change. The results show that the direct impact of climate change and the impact of Frozen Ground degradation can explain 55% and 33%, respectively, of the streamflow decrease for the entire SRYR from Period 1 (1965–1989) to Period 2 (1990–2003). In the permafrost-dominated region upstream of the Jimai hydrological station, the impact of Frozen Ground degradation can explain 71% of the streamflow decrease. From Period 2 (1990–2003) to Period 3 (2004–2015), the observed streamflow did not increase as much as the precipitation; this could be attributed to the combined effects of increasing potential evapotranspiration and more importantly, Frozen Ground degradation. Frozen Ground degradation could influence streamflow by increasing the Groundwater storage when the active layer thickness increases in permafrost-dominated regions. These findings will help develop a better understanding of the impact of Frozen Ground degradation on water resources in the Tibetan Plateau.
Tingjun Zhang - One of the best experts on this subject based on the ideXlab platform.
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change in Frozen soils and its effect on regional hydrology upper heihe basin northeastern qinghai tibetan plateau
The Cryosphere, 2018Co-Authors: Bing Gao, Yanlin Zhang, Dawen Yang, Yue Qin, Yuhan Wang, Tingjun ZhangAbstract:Abstract. Frozen Ground has an important role in regional hydrological cycles and ecosystems, particularly on the Qinghai–Tibetan Plateau (QTP), which is characterized by high elevations and a dry climate. This study modified a distributed, physically based hydrological model and applied it to simulate long-term (1971–2013) changes in Frozen Ground its the effects on hydrology in the upper Heihe basin, northeastern QTP. The model was validated against data obtained from multiple Ground-based observations. Based on model simulations, we analyzed spatio-temporal changes in Frozen soils and their effects on hydrology. Our results show that the area with permafrost shrank by 8.8 % (approximately 500 km2), predominantly in areas with elevations between 3500 and 3900 m. The maximum depth of seasonally Frozen Ground decreased at a rate of approximately 0.032 m decade−1, and the active layer thickness over the permafrost increased by approximately 0.043 m decade−1. Runoff increased significantly during the cold season (November–March) due to an increase in liquid soil moisture caused by rising soil temperatures. Areas in which permafrost changed into seasonally Frozen Ground at high elevations showed especially large increases in runoff. Annual runoff increased due to increased precipitation, the base flow increased due to changes in Frozen soils, and the actual evapotranspiration increased significantly due to increased precipitation and soil warming. The Groundwater storage showed an increasing trend, indicating that a reduction in permafrost extent enhanced the Groundwater recharge.
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relict mountain permafrost area loess plateau china exhibits high ecosystem respiration rates and accelerating rates in response to warming
Journal of Geophysical Research, 2017Co-Authors: Cuicui Mu, Xiaodong Wu, Qian Zhao, Joseph M Smoak, Yulong Yang, Lian Hu, Wen Zhong, Haiyan Xu, Tingjun ZhangAbstract:Relict permafrost regions are characterized by thin permafrost and relatively high temperatures. Understanding the ecosystem respiration rate (ERR) and its relationship with soil hydrothermal conditions in these areas can provide knowledge regarding the permafrost carbon cycle in a warming world. In this study, we examined a permafrost area, a boundary area, and a seasonally Frozen Ground area within a relict permafrost region on the east edge of the Qinghai-Tibetan Plateau, China. Measurements from July 2015 to September 2016 showed that the mean annual ecosystem CO2 emissions for the boundary area were greater than the permafrost area. The Q10 value of the ERRs in the seasonally Frozen Ground area was greater than the permafrost area, indicating that the carbon emissions in the nonpermafrost areas were more sensitive to warming. The 1 year open-top chamber (OTC) warming increased soil temperatures in both the permafrost and seasonally Frozen Ground areas throughout the year, and the warming increased the ERRs by 1.18 (0.99–1.38, with interquartile range) and 1.13 (0.75–1.54, with interquartile range) μmol CO2 m−2 s−1 in permafrost and seasonally Frozen Ground areas, respectively. The OTC warming increased annual ERRs by approximately 50% for both permafrost and seasonally Frozen Ground areas with half the increase occurring during the nongrowing seasons. These results suggest that the ERRs in relict permafrost are high in comparison with arctic regions, and the carbon balance in relict permafrost areas could be greatly changed by climate warming.
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change in Frozen soils and its effect on regional hydrology in the upper heihe basin the northeast qinghai tibetan plateau
The Cryosphere Discussions, 2017Co-Authors: Bing Gao, Yanlin Zhang, Dawen Yang, Yue Qin, Yuhan Wang, Tingjun ZhangAbstract:Abstract. Frozen Ground has an important role in regional hydrological cycle and ecosystem, especially on the Qinghai-Tibetan Plateau, which is characterized by high elevation and a dry climate. This study modified a distributed physically-based hydrological model and applied it to simulate the long-term (from 1961 to 2013) change of Frozen Ground and its effect on hydrology in the upper Heihe basin located at Northeast Qinghai-Tibetan Plateau. The model was validated carefully against data obtained from multiple Ground-based observations. The model results showed that the permafrost area shrank by 9.5 % (approximately 600 km2), especially in areas with elevation between 3500 m and 3900 m. The maximum Frozen depth of seasonally Frozen Ground decreased at a rate of approximately 4.1 cm/10 yr, and the active layer depth over the permafrost increased by about 2.2 cm/10 yr. Runoff increased significantly during cold seasons (November–March) due to the increase in liquid soil moisture caused by rising soil temperature. Areas where permafrost changed into the seasonally Frozen Ground at high elevation showed especially large changes in runoff. Annual runoff increased due to increased precipitation, the base flow increased due to permafrost degradation, and the actual evapotranspiration increased significantly due to increased precipitation and soil warming. The Groundwater storage showed an increasing trend, which indicated that the Groundwater recharge was enhanced due to the degradation of permafrost in the study area.
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satellite remote sensing of permafrost and seasonally Frozen Ground
Geophysical monograph, 2013Co-Authors: Claude R Duguay, Tingjun Zhang, David W Leverington, V E RomanovskyAbstract:Permafrost consists of Ground materials that have remained at or below 0°C for two or more years, while seasonally Frozen Ground refers to Ground that freezes and thaws annually. Permafrost and seasonally Frozen Ground parameters are difficult to measure directly from remote sensing data since they are related to subsurface phenomena. Until recently, relatively few studies had examined the potential of remote sensing techniques for mapping the spatial distribution of near-surface permafrost, the properties of the active layer (the uppermost portion of the Ground that freezes and thaws on an annual basis), and seasonally Frozen Ground in non-permafrost regions. In addition, few studies had made use of satellite imagery to map features indicative of the presence of near-surface permafrost or of the occurrence of permafrost degradation. Currently, high-resolution satellite images, such as those generated by sensors on board the IKONOS and QuickBird satellites, as well as declassified images generated by the CORONA spy satellite, are being used in conjunction with older aerial photographs to identify changes that have occurred in permafrost terrain in recent decades. Some of the most important advances in recent years have involved (1) the use of parameters related to permafrost conditions (including digital databases of topography and surface cover) to indirectly infer permafrost conditions over large areas by using remote-sensing classification algorithms and Ground-truth data and (2) the development of active and passive microwave techniques to monitor near-surface soil freeze/thaw status at regional to continental scales. These recent advances, as well as potential areas of future development, are covered in this chapter.
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an observational 71 year history of seasonally Frozen Ground changes in the eurasian high latitudes
Environmental Research Letters, 2011Co-Authors: Oliver W Frauenfeld, Tingjun ZhangAbstract:In recent decades, significant changes have occurred in high-latitude areas, particularly to the cryosphere. Sea ice extent and thickness have declined. In land areas, glaciers and ice sheets are experiencing negative mass balance changes, and there is substantial regional snow cover variability. Subsurface changes are also occurring in northern soils. This study focuses on these changes in the soil thermal regime, specifically the seasonally Frozen Ground region of Eurasia. We use a database of soil temperatures at 423 stations and estimate the maximum annual soil freezing depth at the 387 sites located on seasonally Frozen Ground. Evaluating seasonal freeze depth at these sites for 1930?2000 reveals a statistically significant trend of ?4.5?cm/decade and a net change of ?31.9?cm. Interdecadal variability is also evident such that there was no trend until the late 1960s, after which seasonal freeze depths decreased significantly until the early 1990s. From that point forward, likely through at least 2008, no change is evident. These changes in the soil thermal regime are most closely linked with the freezing index, but also mean annual air temperatures and snow depth. Antecedent conditions from the previous warm season do not appear to play a large role in affecting the subsequent cold season?s seasonal freeze depths. The strong decrease in seasonal freeze depths during the 1970s to 1990s was likely the result of strong atmospheric forcing from the North Atlantic Oscillation during that time period.
Yuhan Wang - One of the best experts on this subject based on the ideXlab platform.
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data driven mapping of the spatial distribution and potential changes of Frozen Ground over the tibetan plateau
Science of The Total Environment, 2019Co-Authors: Taihua Wang, Dawen Yang, Yue Qin, Beijing Fang, Wencong Yang, Yuhan WangAbstract:Abstract Frozen Ground degradation profoundly impacts the hydrology, ecology and human society on the Tibetan Plateau (TP) and the downstream regions. The spatial distribution and potential changes of permafrost and maximum thickness of seasonally Frozen Ground (MTSFG) on the TP is of great importance and needs more in-depth studies. This study maps the permafrost and MTSFG distribution in the baseline period (2003−2010) and in the future (2040s and 2090s) with 1-km resolution. Logistic regression (LR), support vector machine (SVM) and random forest (RF) are validated using 106 borehole observations and proved to be applicable in estimating permafrost distribution. According to the majority voting results of the three algorithms, 45.9% area of the TP is underlain by permafrost in the baseline period, and respectively 25.9% and 43.9% of the current permafrost will disappear by the 2040s and the 2090s projected by mean of the projections from the five General Circulation Models under the Representative Concentration Pathway 4.5 scenario. SVM performs better in spatial generalization than RF based on the results of nested cross validation. According to the MTSFG results derived from SVM, the most dramatic decrease in MTSFG will occur in the southwestern TP, which is projected to exceed 50 cm in the 2090s compared with the baseline period. This study introduces the statistics and machine learning algorithms to Frozen Ground estimation on the TP, and the high resolution permafrost and MTSFG maps produced by this study can provide useful information for future studies on the third pole region.
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Frozen Ground degradation may reduce future runoff in the headwaters of an inland river on the northeastern tibetan plateau
Journal of Hydrology, 2018Co-Authors: Yuhan Wang, Bing Gao, Yue Qin, Taihua Wang, Hanbo Yang, Dawen YangAbstract:Abstract On the Tibetan Plateau, climate change, particularly increases in air temperature, significantly affects cryospheric and hydrological processes. Based on 5 typical future climate scenarios from the Coupled Model Intercomparison Project (CMIP5) under emission scenario RCP4.5 and a distributed ecohydrological model (GBEHM), this study analyzes the potential characteristics of future climate change (from 2011 to 2060) and the associated effects on the cryospheric and hydrological processes in the upper Heihe River Basin, a typical cold mountain region located on the northeastern Tibetan Plateau. The precipitation, air temperature, and Frozen Ground elasticities of runoff/evapotranspiration are then estimated based on the simulation results. The typical future climate scenarios suggest that air temperature will increase at an average rate of 0.34 °C/10a in the future and that precipitation will increase slightly by 6 mm/10a under the RCP 4.5 emission scenario. Based on the GBEHM-simulated results, due to the increase in air temperature, glaciers would be reduced to less than 100 million m3 by 2060, the permafrost area would shrink by 23%, the maximum Frozen depth of seasonally Frozen Ground would decrease by 5.4 cm/10a and the active layer depth of the Frozen Ground would increase by 6.1 cm/10a. Additionally, runoff would decrease by approximately 5 mm/10a, and evapotranspiration would increase by approximately 9 mm/10a. The estimated elasticities indicate that annual runoff would decrease at an average rate of 24 mm/°C and evapotranspiration would increase at an average rate of 21 mm/°C with rising air temperature in the future. The impacts of increased air temperature on hydrological processes are mainly due to changes in Frozen Ground. The thickening of the active layer of the Frozen Ground increases the soil storage capacity, leading to decreased runoff and increased evapotranspiration. When the active layer depth increases by 1 cm, annual runoff decreases by approximately 1.3 mm, and annual evapotranspiration increases by approximately 0.9 mm. In addition, the shift from permafrost to seasonal Frozen Ground increases Groundwater infiltration, which decreases surface runoff. Compared to that over the past 50 years, the effect of increased air temperature on the Frozen Ground in the upper Heihe River Basin will be greater in the future, which would result in a faster reduction in runoff in the future considering the effects of global warming.
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historical and future changes of Frozen Ground in the upper yellow river basin
Grid and Pervasive Computing, 2018Co-Authors: Taihua Wang, Dawen Yang, Bing Gao, Yue Qin, Yuhan Wang, Yun Chen, Hanbo YangAbstract:Abstract Frozen Ground degradation resulting from climate warming on the Tibetan Plateau has aroused wide concern in recent years. In this study, the maximum thickness of seasonally Frozen Ground (MTSFG) is estimated by the Stefan equation, which is validated using long-term Frozen depth observations. The permafrost distribution is estimated by the temperature at the top of permafrost (TTOP) model, which is validated using borehole observations. The two models are applied to the upper Yellow River Basin (UYRB) for analyzing the spatio-temporal changes in Frozen Ground. The simulated results show that the areal mean MTSFG in the UYRB decreased by 3.47 cm/10 a during 1965–2014, and that approximately 23% of the permafrost in the UYRB degraded to seasonally Frozen Ground during the past 50 years. Using the climate data simulated by 5 General Circulation Models (GCMs) under the Representative Concentration Pathway (RCP) 4.5, the areal mean MTSFG is projected to decrease by 1.69 to 3.07 cm/10 a during 2015–2050, and approximately 40% of the permafrost in 1991–2010 is projected to degrade into seasonally Frozen Ground in 2031–2050. This study provides a framework to estimate the long-term changes in Frozen Ground based on a combination of multi-source observations at the basin scale, and this framework can be applied to other areas of the Tibetan Plateau. The estimates of Frozen Ground changes could provide a scientific basis for water resource management and ecological protection under the projected future climate changes in headwater regions on the Tibetan Plateau.
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quantifying the streamflow response to Frozen Ground degradation in the source region of the yellow river within the budyko framework
Journal of Hydrology, 2018Co-Authors: Taihua Wang, Dawen Yang, Yue Qin, Hanbo Yang, Yuhan WangAbstract:Abstract The source region of the Yellow River (SRYR) is greatly important for water resources throughout the entire Yellow River Basin. Streamflow in the SRYR has experienced great changes over the past few decades, which is closely related to the Frozen Ground degradation; however, the extent of this influence is still unclear. In this study, the air freezing index (DDFa) is selected as an indicator for the degree of Frozen Ground degradation. A water-energy balance equation within the Budyko framework is employed to quantify the streamflow response to the direct impact of climate change, which manifests as changes in the precipitation and potential evapotranspiration, as well as the impact of Frozen Ground degradation, which can be regarded as part of the indirect impact of climate change. The results show that the direct impact of climate change and the impact of Frozen Ground degradation can explain 55% and 33%, respectively, of the streamflow decrease for the entire SRYR from Period 1 (1965–1989) to Period 2 (1990–2003). In the permafrost-dominated region upstream of the Jimai hydrological station, the impact of Frozen Ground degradation can explain 71% of the streamflow decrease. From Period 2 (1990–2003) to Period 3 (2004–2015), the observed streamflow did not increase as much as the precipitation; this could be attributed to the combined effects of increasing potential evapotranspiration and more importantly, Frozen Ground degradation. Frozen Ground degradation could influence streamflow by increasing the Groundwater storage when the active layer thickness increases in permafrost-dominated regions. These findings will help develop a better understanding of the impact of Frozen Ground degradation on water resources in the Tibetan Plateau.
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change in Frozen soils and its effect on regional hydrology upper heihe basin northeastern qinghai tibetan plateau
The Cryosphere, 2018Co-Authors: Bing Gao, Yanlin Zhang, Dawen Yang, Yue Qin, Yuhan Wang, Tingjun ZhangAbstract:Abstract. Frozen Ground has an important role in regional hydrological cycles and ecosystems, particularly on the Qinghai–Tibetan Plateau (QTP), which is characterized by high elevations and a dry climate. This study modified a distributed, physically based hydrological model and applied it to simulate long-term (1971–2013) changes in Frozen Ground its the effects on hydrology in the upper Heihe basin, northeastern QTP. The model was validated against data obtained from multiple Ground-based observations. Based on model simulations, we analyzed spatio-temporal changes in Frozen soils and their effects on hydrology. Our results show that the area with permafrost shrank by 8.8 % (approximately 500 km2), predominantly in areas with elevations between 3500 and 3900 m. The maximum depth of seasonally Frozen Ground decreased at a rate of approximately 0.032 m decade−1, and the active layer thickness over the permafrost increased by approximately 0.043 m decade−1. Runoff increased significantly during the cold season (November–March) due to an increase in liquid soil moisture caused by rising soil temperatures. Areas in which permafrost changed into seasonally Frozen Ground at high elevations showed especially large increases in runoff. Annual runoff increased due to increased precipitation, the base flow increased due to changes in Frozen soils, and the actual evapotranspiration increased significantly due to increased precipitation and soil warming. The Groundwater storage showed an increasing trend, indicating that a reduction in permafrost extent enhanced the Groundwater recharge.
Lin Zhao - One of the best experts on this subject based on the ideXlab platform.
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a 1 km resolution soil organic carbon dataset for Frozen Ground in the third pole
Earth System Science Data, 2021Co-Authors: Dong Wang, Jie Chen, Lin Zhao, Xianhua Wei, Defu Zou, Xiaofan Zhu, Junmin Hao, Amin WenAbstract:Abstract. Soil organic carbon (SOC) is very important in the vulnerable ecological environment of the Third Pole; however, data regarding the spatial distribution of SOC are still scarce and uncertain. Based on multiple environmental variables and soil profile data from 458 pits (depth of 0–1 m) and 114 cores (depth of 0–3 m), this study uses a machine-learning approach to evaluate the SOC storage and spatial distribution at a depth interval of 0–3 m in the Frozen Ground area of the Third Pole region. Our results showed that SOC stocks (SOCSs) exhibited a decreasing spatial pattern from the southeast towards the northwest. The estimated SOC storage in the upper 3 m of the soil profile was 46.18 Pg for an area of 3.27×106 km 2 , which included 21.69 and 24.49 Pg for areas of permafrost and seasonally Frozen Ground, respectively. Our results provide information on the storage and patterns of SOCSs at a 1 km resolution for areas of Frozen Ground in the Third Pole region, thus providing a scientific basis for future studies pertaining to Earth system models. The dataset is open-access and available at https://doi.org/10.5281/zenodo.4293454 (Wang et al., 2020).
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A 1 km resolution soil organic carbon dataset for Frozen Ground in the Third Pole
'Copernicus GmbH', 2021Co-Authors: Dong Wang, Lin Zhao, Xianhua WeiAbstract:Soil organic carbon (SOC) is very important in the vulnerable ecological environment of the Third Pole; however, data regarding the spatial distribution of SOC are still scarce and uncertain. Based on multiple environmental variables and soil profile data from 458 pits (depth of 0–1 m) and 114 cores (depth of 0–3 m), this study uses a machine-learning approach to evaluate the SOC storage and spatial distribution at a depth interval of 0–3 m in the Frozen Ground area of the Third Pole region. Our results showed that SOC stocks (SOCSs) exhibited a decreasing spatial pattern from the southeast towards the northwest. The estimated SOC storage in the upper 3 m of the soil profile was 46.18 Pg for an area of 3.27×106 km2, which included 21.69 and 24.49 Pg for areas of permafrost and seasonally Frozen Ground, respectively. Our results provide information on the storage and patterns of SOCSs at a 1 km resolution for areas of Frozen Ground in the Third Pole region, thus providing a scientific basis for future studies pertaining to Earth system models. The dataset is open-access and available at https://doi.org/10.5281/zenodo.4293454 (Wang et al., 2020).
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comparison of the surface energy budget between regions of seasonally Frozen Ground and permafrost on the tibetan plateau
Atmospheric Research, 2015Co-Authors: Jimin Yao, Lin ZhaoAbstract:Abstract Surface energy budgets were calculated using turbulent flux observation data and meteorological gradient data collected in 2008 from two sites: BJ, located in a seasonally Frozen Ground region, and Tanggula, located in a permafrost region. In 2008, the energy closure ratios for the BJ and Tanggula sites were 0.74 and 0.73, respectively, using 30-min instantaneous energy flux data but 0.87 and 0.99, respectively, using daily average energy flux data. Therefore, the energy closure status is related to the time scale that is used for the study. The variation in the surface energy budget at the two sites was similar: The sensible heat flux ( Hs ) was relatively high in spring and reduced in summer but gradually increased in autumn. The latent heat flux ( LE ) was higher in summer and autumn but lower in winter and spring. Comparably, the starting time for the significant increase in LE occurred earlier at the Tanggula site than that at the BJ site, because the freezing and thawing progress of the active layer of permafrost at Tanggula site significantly affected the Hs and LE distributions, but the freezing and thawing processes of the soil at BJ site did not significantly affect the Hs and LE distributions. The monsoon significantly affected the variation in Hs and LE at both the BJ and Tanggula sites. Regarding the diurnal variation of the energy budget at the two sites, the daily maximum of net radiation ( Rn ) occurred at approximately 14:00 Beijing Time, and the daily maximum of Ground heat flux ( G 0 ) was earlier than those of Hs and LE . The albedo and Bowen ratio for the two sites were both low in summer but high in winter. The albedo increased significantly but the Bowen ratio became lower or even negative when the surface was covered with deep snow.
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changes of climate and seasonally Frozen Ground over the past 30 years in qinghai xizang tibetan plateau china
Global and Planetary Change, 2004Co-Authors: Lin Zhao, Guodong Cheng, Chienlu Ping, Daqing Yang, Yongjian Ding, Shiyin LiuAbstract:Air temperature, Ground surface temperature (GST; 0 cm at depth), precipitation and freezing depth data at 50 meteorological stations in the Qinghai–Tibet Plateau (QTP) were analyzed to examine changes of climate and seasonally Frozen Ground (SFG) in the past 30 years. The latitude, longitude, elevation, mean annual air temperature (MAAT), annual precipitation (AP) and maximum freezing depth at each station were used as the criterions to group the stations by the Hierarchical Cluster Analysis method. Fifty stations were grouped into four clusters, which are distributed in different regions of QTP. The most significant climate warming occurred in northeastern QTP, and the warming trend was greater in the cold season than in the warm season. Annual precipitation (AP) increased in the northwestern, inland and southeastern regions of QTP, but decreased in the northeastern QTP. The most significant changes of seasonally Frozen Ground (SFG) occurred in regions with thickest SFG, i.e., inland QTP, then northeastern and northwestern QTP. The duration of SFG shortened differently in different regions. Significant changes also occurred in the inland and northeastern regions of QTP. The cold season air temperature is the main factor controlling SFG change. The warming trends of Ground surface temperatures are more significant than air temperature, and the warm season warming is greater than cold season warming. Changes of SFG depth, duration and surface temperature are likely to enhance heat exchanges between Ground and atmosphere, in favor of stronger plateau monsoons. D 2004 Elsevier B.V. All rights reserved.
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data driven mapping of the spatial distribution and potential changes of Frozen Ground over the tibetan plateau
Science of The Total Environment, 2019Co-Authors: Taihua Wang, Dawen Yang, Yue Qin, Beijing Fang, Wencong Yang, Yuhan WangAbstract:Abstract Frozen Ground degradation profoundly impacts the hydrology, ecology and human society on the Tibetan Plateau (TP) and the downstream regions. The spatial distribution and potential changes of permafrost and maximum thickness of seasonally Frozen Ground (MTSFG) on the TP is of great importance and needs more in-depth studies. This study maps the permafrost and MTSFG distribution in the baseline period (2003−2010) and in the future (2040s and 2090s) with 1-km resolution. Logistic regression (LR), support vector machine (SVM) and random forest (RF) are validated using 106 borehole observations and proved to be applicable in estimating permafrost distribution. According to the majority voting results of the three algorithms, 45.9% area of the TP is underlain by permafrost in the baseline period, and respectively 25.9% and 43.9% of the current permafrost will disappear by the 2040s and the 2090s projected by mean of the projections from the five General Circulation Models under the Representative Concentration Pathway 4.5 scenario. SVM performs better in spatial generalization than RF based on the results of nested cross validation. According to the MTSFG results derived from SVM, the most dramatic decrease in MTSFG will occur in the southwestern TP, which is projected to exceed 50 cm in the 2090s compared with the baseline period. This study introduces the statistics and machine learning algorithms to Frozen Ground estimation on the TP, and the high resolution permafrost and MTSFG maps produced by this study can provide useful information for future studies on the third pole region.
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Frozen Ground degradation may reduce future runoff in the headwaters of an inland river on the northeastern tibetan plateau
Journal of Hydrology, 2018Co-Authors: Yuhan Wang, Bing Gao, Yue Qin, Taihua Wang, Hanbo Yang, Dawen YangAbstract:Abstract On the Tibetan Plateau, climate change, particularly increases in air temperature, significantly affects cryospheric and hydrological processes. Based on 5 typical future climate scenarios from the Coupled Model Intercomparison Project (CMIP5) under emission scenario RCP4.5 and a distributed ecohydrological model (GBEHM), this study analyzes the potential characteristics of future climate change (from 2011 to 2060) and the associated effects on the cryospheric and hydrological processes in the upper Heihe River Basin, a typical cold mountain region located on the northeastern Tibetan Plateau. The precipitation, air temperature, and Frozen Ground elasticities of runoff/evapotranspiration are then estimated based on the simulation results. The typical future climate scenarios suggest that air temperature will increase at an average rate of 0.34 °C/10a in the future and that precipitation will increase slightly by 6 mm/10a under the RCP 4.5 emission scenario. Based on the GBEHM-simulated results, due to the increase in air temperature, glaciers would be reduced to less than 100 million m3 by 2060, the permafrost area would shrink by 23%, the maximum Frozen depth of seasonally Frozen Ground would decrease by 5.4 cm/10a and the active layer depth of the Frozen Ground would increase by 6.1 cm/10a. Additionally, runoff would decrease by approximately 5 mm/10a, and evapotranspiration would increase by approximately 9 mm/10a. The estimated elasticities indicate that annual runoff would decrease at an average rate of 24 mm/°C and evapotranspiration would increase at an average rate of 21 mm/°C with rising air temperature in the future. The impacts of increased air temperature on hydrological processes are mainly due to changes in Frozen Ground. The thickening of the active layer of the Frozen Ground increases the soil storage capacity, leading to decreased runoff and increased evapotranspiration. When the active layer depth increases by 1 cm, annual runoff decreases by approximately 1.3 mm, and annual evapotranspiration increases by approximately 0.9 mm. In addition, the shift from permafrost to seasonal Frozen Ground increases Groundwater infiltration, which decreases surface runoff. Compared to that over the past 50 years, the effect of increased air temperature on the Frozen Ground in the upper Heihe River Basin will be greater in the future, which would result in a faster reduction in runoff in the future considering the effects of global warming.
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historical and future changes of Frozen Ground in the upper yellow river basin
Grid and Pervasive Computing, 2018Co-Authors: Taihua Wang, Dawen Yang, Bing Gao, Yue Qin, Yuhan Wang, Yun Chen, Hanbo YangAbstract:Abstract Frozen Ground degradation resulting from climate warming on the Tibetan Plateau has aroused wide concern in recent years. In this study, the maximum thickness of seasonally Frozen Ground (MTSFG) is estimated by the Stefan equation, which is validated using long-term Frozen depth observations. The permafrost distribution is estimated by the temperature at the top of permafrost (TTOP) model, which is validated using borehole observations. The two models are applied to the upper Yellow River Basin (UYRB) for analyzing the spatio-temporal changes in Frozen Ground. The simulated results show that the areal mean MTSFG in the UYRB decreased by 3.47 cm/10 a during 1965–2014, and that approximately 23% of the permafrost in the UYRB degraded to seasonally Frozen Ground during the past 50 years. Using the climate data simulated by 5 General Circulation Models (GCMs) under the Representative Concentration Pathway (RCP) 4.5, the areal mean MTSFG is projected to decrease by 1.69 to 3.07 cm/10 a during 2015–2050, and approximately 40% of the permafrost in 1991–2010 is projected to degrade into seasonally Frozen Ground in 2031–2050. This study provides a framework to estimate the long-term changes in Frozen Ground based on a combination of multi-source observations at the basin scale, and this framework can be applied to other areas of the Tibetan Plateau. The estimates of Frozen Ground changes could provide a scientific basis for water resource management and ecological protection under the projected future climate changes in headwater regions on the Tibetan Plateau.
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quantifying the streamflow response to Frozen Ground degradation in the source region of the yellow river within the budyko framework
Journal of Hydrology, 2018Co-Authors: Taihua Wang, Dawen Yang, Yue Qin, Hanbo Yang, Yuhan WangAbstract:Abstract The source region of the Yellow River (SRYR) is greatly important for water resources throughout the entire Yellow River Basin. Streamflow in the SRYR has experienced great changes over the past few decades, which is closely related to the Frozen Ground degradation; however, the extent of this influence is still unclear. In this study, the air freezing index (DDFa) is selected as an indicator for the degree of Frozen Ground degradation. A water-energy balance equation within the Budyko framework is employed to quantify the streamflow response to the direct impact of climate change, which manifests as changes in the precipitation and potential evapotranspiration, as well as the impact of Frozen Ground degradation, which can be regarded as part of the indirect impact of climate change. The results show that the direct impact of climate change and the impact of Frozen Ground degradation can explain 55% and 33%, respectively, of the streamflow decrease for the entire SRYR from Period 1 (1965–1989) to Period 2 (1990–2003). In the permafrost-dominated region upstream of the Jimai hydrological station, the impact of Frozen Ground degradation can explain 71% of the streamflow decrease. From Period 2 (1990–2003) to Period 3 (2004–2015), the observed streamflow did not increase as much as the precipitation; this could be attributed to the combined effects of increasing potential evapotranspiration and more importantly, Frozen Ground degradation. Frozen Ground degradation could influence streamflow by increasing the Groundwater storage when the active layer thickness increases in permafrost-dominated regions. These findings will help develop a better understanding of the impact of Frozen Ground degradation on water resources in the Tibetan Plateau.
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change in Frozen soils and its effect on regional hydrology upper heihe basin northeastern qinghai tibetan plateau
The Cryosphere, 2018Co-Authors: Bing Gao, Yanlin Zhang, Dawen Yang, Yue Qin, Yuhan Wang, Tingjun ZhangAbstract:Abstract. Frozen Ground has an important role in regional hydrological cycles and ecosystems, particularly on the Qinghai–Tibetan Plateau (QTP), which is characterized by high elevations and a dry climate. This study modified a distributed, physically based hydrological model and applied it to simulate long-term (1971–2013) changes in Frozen Ground its the effects on hydrology in the upper Heihe basin, northeastern QTP. The model was validated against data obtained from multiple Ground-based observations. Based on model simulations, we analyzed spatio-temporal changes in Frozen soils and their effects on hydrology. Our results show that the area with permafrost shrank by 8.8 % (approximately 500 km2), predominantly in areas with elevations between 3500 and 3900 m. The maximum depth of seasonally Frozen Ground decreased at a rate of approximately 0.032 m decade−1, and the active layer thickness over the permafrost increased by approximately 0.043 m decade−1. Runoff increased significantly during the cold season (November–March) due to an increase in liquid soil moisture caused by rising soil temperatures. Areas in which permafrost changed into seasonally Frozen Ground at high elevations showed especially large increases in runoff. Annual runoff increased due to increased precipitation, the base flow increased due to changes in Frozen soils, and the actual evapotranspiration increased significantly due to increased precipitation and soil warming. The Groundwater storage showed an increasing trend, indicating that a reduction in permafrost extent enhanced the Groundwater recharge.
