Yafei Sun

Land subsidence in coastal reclamation areas has emerged as one of the critical hidden hazards for coastal cities. This paper presents an integrated InSAR and coastline-change framework for land subsidence monitoring and driving-factor analysis in coastal reclamation cities. Taking the Fangchenggang City, China, as the study area, we utilized 266 scenes of Sentinel-1A SAR images (2016–2025) from the European Space Agency (ESA) and applied time-series SBAS-InSAR to obtain a 10-year time-series monitoring result of land subsidence, with cross-validation against PS-InSAR showing an RMSE below 4 mm at four checkpoints. Furthermore, influencing factors were analyzed by integrating data on coastline changes, precipitation, and groundwater indicators. The conclusions of this paper are as follows: (1) Seven distinct land subsidence funnels in Fangchenggang City from 2016 to 2025 were identified for the first time. Spatially, land subsidence exhibits significant heterogeneity, primarily concentrated in the coastal reclamation areas of the Qisha Peninsula and the Yuwan Peninsula, the maximum subsidence rate reached as high as −163.53 ± 4.90 mm/yr. Temporally, the subsidence rate in the study area shows a gradual deceleration trend over time. (2) The coastline change results from 1964 to 2025 reveal a three-stage temporal characteristic: the land area increased by 2.23 ± 4.51 km², 14.28 ± 6.19 km², and 23.31 ± 4.51 km² during the periods of 1964–1995, 1995–2008, and 2008–2025, respectively. The time-series InSAR results and coastline change results demonstrate that coastal reclamation is the primary factor contributing to land subsidence in this study area. (3) Apart from land reclamation, driving factors such as precipitation and groundwater indicators also show a slight correlation with land subsidence.

In recent decades, glaciers in the southeastern Tibetan Plateau (SETP) have been rapidly melting and showing a large scale of glacier mass loss. Due to the lack of large-scale, high-resolution, and high-precision observations, knowledge on the spatial distribution of the glacier mass balance and the response to climate change is limited in this region. We propose a TanDEM-X bi-static InSAR (Interferometric Synthetic Aperture Radar) algorithm with a non-local mean filter method and difference strategy, to improve the precision of glacier surface elevation change detection. Moreover, we improved the glacier mass balance estimation algorithm with a correction method for multi-source system errors and an uncertainty evaluation method based on error propagation theory to reduce the uncertainty of estimations. We used 13 pairs of TanDEM-X bi-static InSAR images to obtain the glacier mass balance data for the entire SETP. The total area of glaciers monitored was 5821 km² and the total number of glaciers monitored was 2321; the glacier surface elevation change rate was −0.505 ± 0.005 m/yr, and the glacier mass balance estimation was −454.5 ± 13.1 mm w.eq. during 2000–2014. Additionally, we analyzed the spatial distribution of the glacier mass balance within the SETP using the sub-watershed analysis method. The results showed that the mass loss rate had a decreasing trend from the southeast to the northwest. Furthermore, the temperature change and the glacier mass loss rate showed a positive correlation from the southeast to the northwest in this region. This study greatly advances our understanding of the regularities of glacier dynamics in this region, and can provide scientific support for major national goals such as the rational utilization of surrounding water resources and construction of important transportation projects.