Polarimetric L-band PALSAR2 for Discontinuous Permafrost Mapping In Peatland Regions

Abstract

Cost-effective permafrost characterization and monitoring should be possible due to advances in the technology of earth observation satellites. In particular, the long-penetration capabilities of L-band ALOS2-PALSAR2 should permit large scale mapping of discontinuous permafrost in peatland areas. Recently, it has been shown that the long penetrating polarimetric L-band ALOS is very promising for boreal and subractic peatland mapping and monitoring [1], [2]. The unique information provided by the Touzi decomposition [3], [4], and the Touzi scattering phase in particular, on peatland subsurface water flow permits enhanced discrimination of bogs from fens; two peat- land classes that can hardly be discriminated using conventional optical remote sensing. In this study, the Touzi scattering phase is investigated for mapping discontinuous permafrost in peatland regions Northern Alberta. Polarimetric ALOS-2 (FP6-4) and field data were collected in August 2014 over discontinuous distributed within wooded palsa bogs and peat plateaus near the Namur Lake (Northern Alberta). The ALOS2 image is re-calibrated to reduce the residual error from -33 dB down to -43 dB. This permits full exploiting the excellent ALOS2 performance in term of low noise floor (NESZ about -38 dB) to increase the sensitivity of the Touzi phase to deep permafrost. It is shown that the information provided by the scattering type phase permits enhanced mapping of discontinuous permafrost. The results obtained with the long penetrating L-band polarimetric PALSAR2 are much better than the ones obtained with conventional discontinuous permafrost mapping methods based on Lidar and optical (Landsat and Spot) images.