Increased water content in the active layer revealed by regional‐scale InSAR and independent component analysis on the central Qinghai‐Tibet Plateau

Isolating seasonal deformation from Interferometric Synthetic Aperture Radar (InSAR) time-series is critical to quantitative understanding the freeze-thaw processes in permafrost regions. Physics- or statistics-based approaches have been developed to extract seasonal deformation, yet both constraining their evolution in time domain, and thus impeded the quantification of their amplitude variability especially over large scales. By applying Independent Component Analysis (ICA) on Sentinel-1 InSAR measurements during 2015-2019 on the central Qinghai-Tibet Plateau, we reveal that the averaged seasonal deformation is increasing with a linear trend of around 0.17 cm/year. The growing seasonal amplitude is attributed to an 8 cm increase of the Equivalent Water Thickness in the active layer. The results demonstrate the capability of ICA-based decomposition on isolating freeze-thaw-related deformation from other components. The large-scale spatial distribution of varied seasonal deformation can provide new insight into quantifying the water mass balance in vast permafrost regions. Plain Language Summary Permafrost is ground that remains at or below 0 degrees C for at least 2 years. The variations of water content in the seasonally thawed layer underlain by permafrost have strong impacts on the water storage balance, the ecosystems and the infrastructure stability in cold regions. Their inter-annual variations can be reflected by ground deformation, but are hard to quantify over large scales. Here, we apply a satellite remote sensing technique to measure ground deformation during 2015-2019 on the central Qinghai-Tibet Plateau. Using a multivariate statistical method, called independent component analysis, we successfully extract the ground deformation related to the inter-annual soil water variations. We infer the total water content increase in our study area and corroborate it with independent remote sensing products and in-situ measurements. This study demonstrates the potential of remote sensing measurements in characterizing the subsurface soil water variations in cold regions with permafrost.