Time-series ground surface deformation revealed by advanced land observing satellite-2 and Sentinel-1 along the Bei'an-Hei'he highway in Northeast China

Climate warming, human activities and the subsequent warming and thawing of permafrost have led to ground surface instability, threatening infrastructures and indigenous northern communities. The northern Da and Xiao Xing'anling mountain ranges, home to the largest latitudinal permafrost region in China, highlight the importance of monitoring the thermal state of permafrost for understanding climate change and regional economic development. This study utilized 11 scenes of the Advanced Land Observing Satellite-2 (ALOS-2) data and 54 scenes of Sentinel-1 data from March 2018 to December 2019 to evaluate the ground surface deformation of the Bei'an-Hei'he Highway (BHH) in Northeast China. ALOS-2 results showed deformation rates ranging from −30 to +35 mm/year, while Sentinel-1, from −30 to +30 mm/year (negative values indicate subsidence and positive, frost heaving). The subsidence zone (deformation rate exceeding −15 mm/year) was found in areas with significant variations in permafrost temperature (greater than ±0.8°C), and deformation rates correlated positively to daily precipitation and air temperature. Thaw settlement was predominantly observed in areas at low elevations (140 to 425 m) and on gentle slope angles (2–6°), affecting both south- and north-facing slopes. A comparison of data sources revealed that ALOS-2 data were more sensitive to areas with high normalized difference vegetation index (NDVI) values, while Sentinel-1 provided more detailed deformation data in regions with low NDVI. This study contributes valuable data and ongoing assessments for road surface stability in permafrost regions of Northeast China.