Monitoring permafrost changes in the Yangtze River source region of the Qinghai-Tibetan Plateau using differential SAR interferometry

Qinghai-Tibet Plateau (QTP) is the largest high-altitude permafrost zone in the mid-latitudes. It is also the source region of major rivers in Southeast and East Asia, referred to as the "Water Tower of Asia". Large hydrologic changes have been observed in the Yangtze River source region and adjacent areas in the early 21st century. The contribution of permafrost degradation and loss of ground ice to the hydrologic changes is however still lacking. In permafrost areas, the seasonal freeze-thaw cycle in the active layer causes seasonal upward and downward ground motion because of ice-water phase transition process; under climate warming, thawing of the permafrost causes long-term subsidence. The surface deformation reflects the changes in the permafrost active layer and the ground ice. This study monitors ground deformation in permafrost terrain (1991-now) by applying Small BAseline Subset InSAR (SBAS-InSAR) technique using C-band ERS, ENVISAT, Sentinel-1 and L-band ALOS PALSAR datasets; reveals the spatial and temporal characteristics of the changes in the permafrost active layer and the ground ice. The study provides data support for studying the hydrologic changes in the Yangtze River source region.