Assessment of an InSAR based soil moisture index across Arctic permafrost regions.

Identifying soil moisture in permafrost regions is crucial for various applications, yet it remains challenging with standard remote sensing techniques due to the high heterogeneity of the landscape. Soil wetness plays a significant role in these regions, facilitating processes such as the upscaling of carbon fluxes. Seasonal thawing and freezing of near-surface soil, in the presence of ice, cause subsidence-heave cycles with magnitudes reaching centimeters.

A recent study with focus on central Yamal showed that Sentinel-1 InSAR detects pronounced subsidence in areas with higher soil moisture using the relationship between thawing degree days and surface deformation. In this study, we extended the analysis to multiple site-specific study areas across the entire Arctic, and its performance is evaluated against other commonly used remote sensing global soil moisture products (CCI, SMAP, SMOS), reanalysis (ERA5) and in-situ measurements. Soil moisture data from various field campaigns were compiled via data mining for this purpose. Furthermore, a landscape-scale analysis is conducted to quantify biases across various terrain types and to identify wetness gradients across the study sites.

It can be demonstrated that the InSAR approach offers a valuable tool for distinguishing wet and dry landscape features, which is significant for monitoring permafrost degradation in Arctic lowland regions.