Characterization of Permafrost Active Layer using Polarimetric SAR and Ground Data over North-Western Indian Himalaya

The dynamics of the Thawing Front (TF), as the transition zone between unfrozen and frozen soil within permafrost active layer, and Permafrost Table (PT) have critical inference towards permafrost degradation, which has close link-age with climate change, hydrological cycle and geohazards. In this article, sensitivity analysis of multi-frequency polarimetric SAR observations along with in-situ measurements are carried out to characterize freezing behavior of the permafrost active layer using TF and PT. This novel methodology comprises, (a) in-situ sub-surface soil moisture and dielectric profiling (upto ~1.5m depth) at selected sites, (b) delineation of TF and active layer thickness upto PT, and (c) correlation of dual-frequency L & C-band polarimetric SAR observations with the depth, soil moisture and dielectric properties at the TF. The result shows that L-band SAR has a very strong sensitivity (R
²
> 0.85) towards the depth of occurrence, soil moisture and dielectric properties at TF in different polarization channels. However, C-band SAR observation shows weak correlation with the TF properties. Most likely, this seems to be first of its kind study in Indian Himalayas, integrating ground and space-borne observations for characterizing freezing condition of the permafrost active layers. The study has a strong implication in deciphering the occurrence of permafrost in regional scale. In addition, multi-temporal observations will be helpful to delineate the Thawing Front dynamics with further significance towards degradation of permafrost deposits.