###### Abstract  
In this study, polarimetric Synthetic Aperture Radar (PolSAR) data at X-, C- and L-Bands, acquired by the satellites: TerraSAR-X (2011), Radarsat-2 (2011), ALOS (2010) and ALOS-2 (2016), were used to characterize the tundra land cover of a test site located close to the town of Tuktoyaktuk, NWT, Canada. Using available in situ ground data collected in 2010 and 2012, we investigate PolSAR scattering characteristics of common tundra land cover classes at X-, C- and L-Bands. Several decomposition features of quad-, co-, and cross-polarized data were compared, the correlation between them was investigated, and the class separability offered by their different feature spaces was analyzed. Certain PolSAR features at each wavelength were sensitive to the land cover and exhibited distinct scattering characteristics. Use of shorter wavelength imagery (X and C) was beneficial for the characterization of wetland and tundra vegetation, while L-Band data highlighted differences of the bare ground classes better. The Kennaugh Matrix decomposition applied in this study provided a unified framework to store, process, and analyze all data consistently, and the matrix offered a favorable feature space for class separation. Of all elements of the quad-polarized Kennaugh Matrix, the intensity based elements K0, K1, K2, K3 and K4 were found to be most valuable for class discrimination. These elements contributed to better class separation as indicated by an increase of the separability metrics squared Jefferys Matusita Distance and Transformed Divergence. The increase in separability was up to 57% for Radarsat-2 and up to 18% for ALOS-2 data. PolSAR; dual polarimetry; quad polarimetry; decomposition; TerraSAR-X; Radarsat-2; ALOS; ALOS-2; tundra; arctic +
Footnote †: journal: Applied Soft  
comprehending temporal and spatial changes. Several studies have therefore investigated the use of SAR, PolSAR, and SAR interferometry (InSAR) for characterizing Arctic land surfaces, particularly that of tundra environments. Table 1 provides an overview of select studies that involved the use of active microwave imaging of Arctic tundra environments. As can be observed, shortwave C- and X-Band data were frequently used for the characterization of land cover and shoreline types, and most studies incorporated analysis of polarimetric information to relate observed values with certain types or states of the land surface [1; 2; 3; 4; 5; 6; 7; 8; 9; 10; 11; 12; 13; 14; 15; 16]. C-Band and L-Band data stacks have been used primarily to determine surface movements in permafrost regions using interferometry [17; 18; 19; 20; 21]. This is likely driven by the opening of the ALOS archive and the capacity of the L-Band microwaves to penetrate the relatively small tundra vegetation, typically resulting in higher interferometric coherence, and leading to a more reliable estimate of surface movements. The seasonal thawing and freezing of the active layer is also a promising area for InSAR applications, and estimation of the active layer thickness/variations across the entirety of the Arctic is of particular importance considering recent warming trends [22; 23; 24]. Most of the studies identified in Table 1, employed data of a single sensor and only few involved multi-frequency SAR/PolSAR/InSAR information, e.g., dealing with some combination of X-, C- or L-Band data [8; 11; 14; 17]. Among the selected studies, the quad-polarization mode of Radarsat-2 was most frequently employed, followed by the dual HH/HV-polarization mode of ALOS and TerraSAR-X,