Ongoing climate warming and increased human activities have led to significant permafrost degradation on the Qinghai-Tibet Plateau (QTP). Mapping the distribution of active layer thickness (ALT) can provide essential information for understanding this degradation. Over the past decade, InSAR (Interferometric synthetic aperture radar) technology has been utilized to estimate ALT based on remotely-sensed surface deformation information. However, these methods are generally limited by their ability to accurate extract seasonal deformation and model subsurface water content of active layer. In this paper, an ALT inversion method considering both seasonal deformation from InSAR and smoothly multilayer soil moisture from ERA5 is proposed. Firstly, we introduce a ground seasonal deformation extraction model combining RobustSTL and InSAR, and the deformation extraction accuracy by considering the deformation characteristics of permafrost are evaluated, proving the effectiveness of RobustSTL in extracting seasonal deformation of permafrost. Then, using ERA5 soil moisture products, a smoothed multilayer soil moisture model for ALT inversion is established. Finally, integrating the seasonal deformation and multilayer soil moisture, the ALT can be estimated. The proposed model is applied to the Yellow River source region (YRSR) with Sentinel-1A images acquired from 2017 to 2021, and the ALT retrieval accuracy is validated with measured data. Experimental results show that the vertical deformation rate of the study area generally ranges from -30 mm/year to 20 mm/year, with seasonal deformation amplitude ranging from 2 mm to 30 mm. The RobustSTL method has the highest accuracy in extracting seasonal deformation of permafrost, with an RMSE (root mean square error) of 0.69 mm, and is capable of capturing the freeze-thaw characteristics of the active layer. The estimated ALT of the YRSR ranges from 49 cm to 450 cm, with an average value of 145 cm. Compared to the measured data, the proposed method has an average error of 37.5 cm, which represents a 21 % improvement in accuracy over existing methods.

冻土的水-冰相变交替过程会造成水文环境与地表工程的破坏，从而导致路基塌陷、山体滑坡、洪水暴发以及冰川溃决等灾害，智能感知潜在风险对保护冻土区工程建筑具有重要意义。采用2017年01月—2023年04月194景Sentinel-1A 影像，利用SBAS-InSAR技术获取了黄河上游沱沱河盆地冻土区形变结果，冻土地表形变明显且空间分布不均匀，监测时间段内最大形变速率可达13 mm/年。冻土区青藏铁路路基形变呈现“冻胀融沉”的季节性变化，暖季匀速沉降，冷季缓慢抬升，在气候变暖背景下暖季逐渐长于冷季；分别将InSAR监测结果与近7年沱沱河盆地GNSS监测数据对比，两者趋势一致；引入降水和气温因素后发现冻土区形变具有显著聚集特征，在人类活动频繁地区存在较大形变。该研究对冻土防灾减灾、保障人民生命财产安全具有重要意义，为高纬度冻土工程建设提供一定借鉴。

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.

The Qilian Mountains, located on the northeastern edge of the Qinghai-Tibet Plateau, are characterized by unique high-altitude and cold-climate terrain, where permafrost and seasonally frozen ground are extensively distributed. In recent years, with global warming and increasing precipitation on the Qinghai-Tibet Plateau, permafrost degradation has become severe, further exacerbating the fragility of the ecological environment. Therefore, timely research on surface deformation and the freeze-thaw patterns of alpine permafrost in the Qilian Mountains is imperative. This study employs Sentinel-1A SAR data and the SBAS-InSAR technique to monitor surface deformation in the alpine permafrost regions of the Qilian Mountains from 2017 to 2023. A method for spatiotemporal interpolation of ascending and descending orbit results is proposed to calculate two-dimensional surface deformation fields further. Moreover, by constructing a dynamic periodic deformation model, the study more accurately summarizes the regular changes in permafrost freeze-thaw and the trends in seasonal deformation amplitudes. The results indicate that the surface deformation time series in both vertical and east-west directions obtained using this method show significant improvements in accuracy over the initial data, allowing for a more precise reflection of the dynamic processes of surface deformation in the study area. Subsidence is predominant in permafrost areas, while uplift mainly occurs in seasonally frozen ground areas near lakes and streams. The average vertical deformation rate is 1.56 mm/a, with seasonal amplitudes reaching 35 mm. Topographical (elevation; slope gradient; aspect) and climatic factors (temperature; soil moisture; precipitation) play key roles in deformation patterns. The deformation of permafrost follows five distinct phases: summer thawing; warm-season stability; frost heave; winter cooling; and spring thawing. This study enhances our understanding of permafrost deformation characteristics in high-latitude and high-altitude regions, providing a reference for preventing geological disasters in the Qinghai-Tibet Plateau area and offering theoretical guidance for regional ecological environmental protection and infrastructure safety.

Under the interference of climate warming and human engineering activities, the degradation of permafrost causes the frequent occurrence of geological disasters such as uneven foundation settlement and landslides, which brings great challenges to the construction and operational safety of road projects. In this paper, the spatial and temporal evolution of surface deformations along the Beihei Highway was investigated by combining the SBAS-InSAR technique and the surface frost number model after considering the vegetation factor with multi-source remote sensing observation data. After comprehensively considering factors such as climate change, permafrost degradation, anthropogenic disturbance, and vegetation disturbance, the surface uneven settlement and landslide processes were analyzed in conjunction with site surveys and ground data. The results show that the average deformation rate is approximately -16 mm/a over the 22 km of the study area. The rate of surface deformation on the pavement is related to topography, and the rate of surface subsidence on the pavement is more pronounced in areas with high topographic relief and a sunny aspect. Permafrost along the roads in the study area showed an insignificant degradation trend, and at landslides with large surface deformation, permafrost showed a significant degradation trend. Meteorological monitoring data indicate that the annual minimum mean temperature in the study area is increasing rapidly at a rate of 1.266 degrees C/10a during the last 40 years. The occurrence of landslides is associated with precipitation and freeze-thaw cycles. There are interactions between permafrost degradation, landslides, and vegetation degradation, and permafrost and vegetation are important influences on uneven surface settlement. Focusing on the spatial and temporal evolution process of surface deformation in the permafrost zone can help to deeply understand the mechanism of climate change impact on road hazards in the permafrost zone.

多年冻土活动层内部冰-水相变会导致多年冻土地表出现季节性的冻胀和融沉,而其上限处地下冰融化将引起地表的长期沉降,因此揭示地表形变的季节和长期变化规律可为多年冻土变化研究提供新的视角和方法。本文以青藏高原多年冻土区北界(西大滩—昆仑垭口)为研究区,利用C波段降轨Sentinel-1数据,采用SBAS-InSAR技术获取该地区多年冻土2014—2020年的地表形变时间序列结果,并基于长期形变速率和季节性形变量探讨了该地区的多年冻土形变规律。结果表明:在多年冻土北界西大滩沟谷地区,不连续多年冻土区形变空间差异较大,多年冻土区的长期沉降速率和季节性的形变量高于季节冻土区。此外,高温多年冻土地表沉降比低温多年冻土更为显著,形变空间分布特征与地貌单元紧密联系。与西大滩谷地相比,昆仑山垭口地区和楚玛尔河高平原区域的长期形变速率与季节性形变量都明显增大。同时热融湖塘的形成过程与地表形变有着直接的关联,在热融湖塘发展早期,地下冰融化使得区域季节性形变量增大,随着热融湖塘扩张,区域长期沉降速率加剧,热融湖塘进一步发展后,区域季节性形变量可能降低。

阐述了在俄罗斯西伯利亚地区研究多年冻土的重要科学意义，回顾了InSAR技术的发展概况，并以俄罗斯西伯利亚地区东南部的克拉斯诺卡缅斯克区域为例，利用短基线集(SBAS-InSAR)技术处理了Sentinel-1数据，得到了符合冻土季节性变化特征的多年岛状冻土形变结果。

In this study, we applied small baseline subset-interferometric synthetic aperture radar (SBAS-InSAR) to monitor the ground surface deformation from 2017 to 2020 in the permafrost region within an ~400 km x 230 km area covering the northern and southern slopes of Mt. Geladandong, Tanggula Mountains on the Tibetan Plateau. During SBAS-InSAR processing, we inverted the network of interferograms into a deformation time series using a weighted least square estimator without a preset deformation model. The deformation curves of various permafrost states in the Tanggula Mountain region were revealed in detail for the first time. The study region undergoes significant subsidence. Over the subsiding terrain, the average subsidence rate was 9.1 mm/a; 68.1% of its area had a subsidence rate between 5 and 20 mm/a, while just 0.7% of its area had a subsidence rate larger than 30 mm/a. The average peak-to-peak seasonal deformation was 19.7 mm. There is a weak positive relationship (~0.3) between seasonal amplitude (water storage in the active layer) and long-term deformation velocity (ground ice melting). By examining the deformation time series of subsiding terrain with different subsidence levels, we also found that thaw subsidence was not restricted to the summer and autumn thawing times but could last until the following winter, and in this circumstance, the winter uplift was greatly weakened. Two import indices for indicating permafrost deformation properties, i.e., long-term deformation trend and seasonal deformation magnitude, were extracted by direct calculation and model approximations of deformation time series and compared with each other. The comparisons showed that the long-term velocity by different calculations was highly consistent, but the intra-annual deformation magnitudes by the model approximations were larger than those of the intra-annual highest-lowest elevation difference. The findings improve the understanding of deformation properties in the degrading permafrost environment.

作为气候变化"指示器"的青藏高原多年冻土,近几十年来受到越来越多学者关注。但是已有冻土区地表形变的研究,多单纯针对地表抬升和沉降量进行分析,鲜有针对不同高寒草地类型进行深入挖掘的。在位于青藏高原多年冻土区腹地的五道梁地区,利用ASAR数据和SBAS-InSAR方法反演了区域内2005年4月到2010年7月的地表形变状况。结果显示研究区地表形变速率基本位于±8 mm/a之间。其中,变形率为正、地表呈现抬升的区域占57.70%,地表形变为负、地表沉降的区域占42.30%。此外,高寒草地整体表现地表下沉的现象,而且高寒草原的地表沉降现象明显强于高寒草甸地区。计算获得3种生态遥感指数后,分析地表形变与生态遥感指数的相关性,发现针对不同草地类型,其地表形变的主导因子存在差异。高寒草甸的地表形变有可能更多的受限于温度变化,而高寒草原的地表形变则可能更多的由水分条件所影响。以上研究说明青藏高原多年冻土区植被类型条件越好,地表沉降量越小。因此今后的相关研究需要对植被类型条件差的区域增加更多的关注,因为这些地区易发生地表沉降,导致其生态系统稳定性较差。

As global warming, permafrost has degraded seriously. The ecological security of many regions has faced a serious threat to their ecological environment, especially the Tianshan mountain regions, which is one of the five major animal husbandry production bases. At present, in these regions, most studies focus on glacier analysis and few pieces of research about permafrost measure. According to 39 ENVISAT ASAR imagines, covered form 2003 June 17th to 2010 June 15th, surface deformation in permafrost region was monitored by SBAS-InSAR method. In this paper, the principles of deformation algorithm were introduced first. When generating the connection graph of the single look complex image of ASAR dataset, there was 126 differential interferogram based on 500 m and 550 days for temporal and spatial baseline respectively. Because of Spatio-temporal baselines and the Doppler centroid difference, 6 ASAR imagines were not generated the connection graph. Then using STRM V4 DEM, 52 low-quality pair of interferogram were eliminated, after the processes of interferograms flattening, adaptive filter, coherence generation and unwrapping. The ground deformation results of the study area were calculated by external ground control points, refinement and re-flattening, estimation of displacement velocity and residual deformation, coherence threshold control, SVD, spatially low-path filtering and temporally high-path filtering. There were 33 results of ground deformation, which covered from 2004 to 2010. According to the deformation results, there were different subsidence and uplift phenomenon in study areas. The deformation rate of the overall study area was no more than +/- 5 cm . yr(-1), and its average deformation rate was < 0. 07 +/- 3. 38) mm . yr(-1). It is indicating that there is a slight subsidence phenomenon in the study area. With the altitude of 3 000 m, the deformation changing mechanism were excavated for the plains and mountain areas distributed by seasonal frozen ground and permafrost respectively. From the research results, deformations in the plain region were uplift except for deformations in the area near cities were subsidence largely. In the mountainous region, the deformations were very scattered than them in the plain region. The overall trend of deformations of the mountain was dominated by subsidence, and subsidence and uplift in the western and eastern regions respectively. There were 15 198 deformation points, which altitude were more than 3 000 m. The annual variation mechanisms of temperature and precipitation about overall deformation points and different deformation intervals points were demonstrated by temperature and precipitation dataset. The results showed that both trends of them have a gradual warming phenomenon. The numbers of deformation rate points about different intervals were 6 364, 6 449 and 2 385 for rates lower than -2. 0 cm . yr(-1), from -2. 0 to 2. 0 cm . yr(-1)( )and higher than 2. 0 cm . yr(-1) in the study mountainous region respectively. Points with negative values were more than points with positive values in the mountainous region, which reflected that subsidence positions were more than uplift positions. This result was also consistent with that global warming cause permafrost degradation then ground subsided. In this paper, the ground deformation results of the study area were successfully calculated by ASAR dataset which was active microwave spectrum. Meanwhile, the deformation results were discussed and prospected in the respects of space, time and the time lag of the permafrost deformation. The study results could provide a new way and reference for the monitoring of permafrost deformation in the Tianshan mountain region.