Spatiotemporal Variations of Freezing and Thawing Indices During the Past Four Decades in Tibet

Liao, Ying; Li, Yiying; Fan, Jihui; Galoie, Majid; Motamedi, Artemis

doi:10.3389/fevo.2021.750961

Cited by 7 publications

(3 citation statements)

References 59 publications

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“…The surface freezing number model uses the ratio of the surface freezing index to the thawing index to divide the boundaries of different frozen soil types [30].…”

Section: Division Methods Of Permafrost Degradation Zonementioning

confidence: 99%

Response of Vegetation to Drought in the Source Region of the Yangtze and Yellow Rivers Based on Causal Analysis

Lu,

Qin,

Yan

et al. 2024

Remote Sensing

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The vegetation and ecosystem in the source region of the Yangtze River and the Yellow River (SRYY) are fragile. Affected by climate change, extreme droughts are frequent and permafrost degradation is serious in this area. It is very important to quantify the drought–vegetation interaction in this area under the influence of climate–permafrost coupling. In this study, based on the saturated vapor pressure deficit (VPD) and soil moisture (SM) that characterize atmospheric and soil drought, as well as the Normalized Differential Vegetation Index (NDVI) and solar-induced fluorescence (SIF) that characterize vegetation greenness and function, the evolution of regional vegetation productivity and drought were systematically identified. On this basis, the technical advantages of the causal discovery algorithm Peter–Clark Momentary Conditional Independence (PCMCI) were applied to distinguish the response of vegetation to VPD and SM. Furthermore, this study delves into the response mechanisms of NDVI and SIF to atmospheric and soil drought, considering different vegetation types and permafrost degradation areas. The findings indicated that low SM and high VPD were the limiting factors for vegetation growth. The positive and negative causal effects of VPD on NDVI accounted for 47.88% and 52.12% of the total area, respectively. Shrubs were the most sensitive to SM, and the response speed of grassland to SM was faster than that of forest land. The impact of SM on vegetation in the SRYY was stronger than that of VPD, and the effect in the frozen soil degradation area was more obvious. The average causal effects of NDVI and SIF on SM in the frozen soil degradation area were 0.21 and 0.41, respectively, which were twice as high as those in the whole area, and SM dominated NDVI (SIF) changes in 62.87% (76.60%) of the frozen soil degradation area. The research results can provide important scientific basis and theoretical support for the scientific assessment and adaptation of permafrost, vegetation, and climate change in the source area and provide reference for ecological protection in permafrost regions.

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“…The surface freezing number model uses the ratio of the surface freezing index to the thawing index to divide the boundaries of different frozen soil types [30].…”

Section: Division Methods Of Permafrost Degradation Zonementioning

confidence: 99%

Response of Vegetation to Drought in the Source Region of the Yangtze and Yellow Rivers Based on Causal Analysis

Lu,

Qin,

Yan

et al. 2024

Remote Sensing

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“…Permafrost degradation is characterized by ground temperature increase [20][21][22][23], AL thickening [24][25][26], and permafrost area reduction [27,28] during the past 30 years. Meanwhile, the timing of the F-T cycle has also exhibited changes due to climate warming and permafrost degradation, which is manifested as the delayed onset of freezing and the advanced onset of thawing, and the extended thawing duration on the QTP [5,[29][30][31][32]. Accurate identification of the timing, duration, and amplitude of seasonal deformation is essential for revealing the hydrothermal state of the AL and is important for the studies of hydrology and ecology in the permafrost regions.…”

Section: Introductionmentioning

confidence: 99%

Characteristics of Freeze–Thaw Cycles in an Endorheic Basin on the Qinghai-Tibet Plateau Based on SBAS-InSAR Technology

et al. 2022

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The freeze–thaw (F-T) cycle of the active layer (AL) causes the “frost heave and thaw settlement” deformation of the terrain surface. Accurately identifying its amplitude and time characteristics is important for climate, hydrology, and ecology research in permafrost regions. We used Sentinel-1 SAR data and small baseline subset-interferometric synthetic aperture radar (SBAS-InSAR) technology to obtain the characteristics of F-T cycles in the Zonag Lake-Yanhu Lake permafrost-affected endorheic basin on the Qinghai-Tibet Plateau from 2017 to 2019. The results show that the seasonal deformation amplitude (SDA) in the study area mainly ranges from 0 to 60 mm, with an average value of 19 mm. The date of maximum frost heave (MFH) occurred between November 27th and March 21st of the following year, averaged in date of the year (DOY) 37. The maximum thaw settlement (MTS) occurred between July 25th and September 21st, averaged in DOY 225. The thawing duration is the thawing process lasting about 193 days. The spatial distribution differences in SDA, the date of MFH, and the date of MTS are relatively significant, but there is no apparent spatial difference in thawing duration. Although the SDA in the study area is mainly affected by the thermal state of permafrost, it still has the most apparent relationship with vegetation cover, the soil water content in AL, and active layer thickness. SDA has an apparent negative and positive correlation with the date of MFH and the date of MTS. In addition, due to the influence of soil texture and seasonal rivers, the seasonal deformation characteristics of the alluvial-diluvial area are different from those of the surrounding areas. This study provides a method for analyzing the F-T cycle of the AL using multi-temporal InSAR technology.

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“…There is a large number of literature studies on the air freezing/thawing index [24,25]. However, most of the current studies on the ground surface freezing/thawing index in China are focused on the Qinghai-Tibet Plateau and the northeastern part of China [26,27]; in addition to these permafrost regions, there are many regions with seasonal permafrost distribution and the transition area between permafrost areas, and the calculation of the freezing/thawing index for the entire Chinese region is important for our understanding of various permafrost and ground surface process changes. In terms of freezing/thawing index prediction, Peng [28] used CMIP5 data to predict the spatial and temporal variation of the freezing/thawing index in the Arctic.…”

Section: Introductionmentioning

confidence: 99%

Variation of Ground Surface Freezing/Thawing Index in China under the CMIP6 Warming Scenarios

Zhang

Melnikov

et al. 2022

Sustainability

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As an important parameter in permafrost research, the annual ground surface freezing/thawing index is widely used in the variation of permafrost. In addition, it is also an important indicator in climatology, providing a large amount of theoretical basis for the assessment of climate change. Based on the ground surface temperature data recorded at 707 meteorological stations from 1960 to 2020, the ground surface freezing/thawing index in China were calculated. The results showed that over the past six decades, the thawing index has shown an upward trend, whereas the freezing index has shown a downward trend, and the trend is stronger around 2000. The results of the R/S-based analysis indicate that the freezing/thawing index will remain on a decreasing/increasing trend for some time to come. Based on the five warming scenarios published by Coupled Model Intercomparison Project Phase 6 (CMIP6), the spatial–temporal variation characteristics of the ground surface freezing/thawing index in China during 2020‒2100 was simulated. It was found that under SSP3‒7.0 and SSP5‒8.5 scenarios, the freezing/thawing index may be 0 °C-days in 2080 and 2070, respectively, which may imply that the ground surface freezing process in some regions of China may disappear.

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Spatiotemporal Variations of Freezing and Thawing Indices During the Past Four Decades in Tibet

Cited by 7 publications

References 59 publications

Response of Vegetation to Drought in the Source Region of the Yangtze and Yellow Rivers Based on Causal Analysis

Response of Vegetation to Drought in the Source Region of the Yangtze and Yellow Rivers Based on Causal Analysis

Characteristics of Freeze–Thaw Cycles in an Endorheic Basin on the Qinghai-Tibet Plateau Based on SBAS-InSAR Technology

Variation of Ground Surface Freezing/Thawing Index in China under the CMIP6 Warming Scenarios

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