Active Layer Thickness Estimation from X-Band SAR Backscatter Intensity

Permafrost covers a large part of Earth's land surface. Due to potential thawing, permafrost may release great amounts of greenhouse gases and have an important role in future global climate. The active layer above the permafrost which seasonally thaws during summer is an important parameter in monitoring the state of permafrost. Its thickness is typically measured locally. By investigating the relation of Active Layer Thickness (ALT) and X-Band SAR backscatter of TerraSAR-X StripMap, we explore the possibility of delineating ALT on a continuous and larger spatial coverage. This study shows that the mutual dependency of ALT and TerraSAR-X backscatter on land cover types induces a connection of both parameters. For the study site of central Yamal a range of 5 dB can be observed for an ALT range of 100 cm (40 - 140 cm) and an R² of 0.66 has been determined over the calibration sites. An increase of ALT with increasing backscatter can be especially determined for ALT > 70 cm. Furthermore the approach is tested for coarser scale and larger spatial coverage by incorporating TerraSAR-X Wide ScanSAR mode.