Kara and Barents sea ice thickness estimation based on CryoSat-2 radar altimeter and Sentinel-1 dual-polarized synthetic aperture radar

Abstract

Abstract. We present a method to combine CryoSat-2 (CS2) radar altimeter and Sentinel-1 synthetic aperture radar (SAR) data to obtain sea ice thickness (SIT) estimates for the Barents and Kara seas. From the viewpoint of tactical navigation, along-track altimeter SIT estimates are sparse, and the goal of our study is to develop a method to interpolate altimeter SIT measurements between CS2 ground tracks. The SIT estimation method developed here is based on the interpolation of CS2 SIT utilizing SAR segmentation and segmentwise SAR texture features. The SIT results are compared to SIT data derived from the AARI ice charts; to ORAS5, PIOMAS and TOPAZ4 ocean–sea ice data assimilation system reanalyses; to combined CS2 and Soil Moisture and Ocean Salinity (SMOS) radiometer weekly SIT (CS2SMOS SIT) charts; and to the daily MODIS (Moderate Resolution Imaging Spectroradiometer) SIT chart. We studied two approaches: CS2 directly interpolated to SAR segments and CS2 SIT interpolated to SAR segments with mapping of the CS2 SIT distributions to correspond to SIT distribution of the PIOMAS ice model. Our approaches yield larger spatial coverage and better accuracy compared to SIT estimates based on either CS2 or SAR data alone. The agreement with modelled SIT is better than with the CS2SMOS SIT. The average differences when compared to ice models and the AARI ice chart SIT were typically tens of centimetres, and there was a significant positive bias when compared to the AARI SIT (on average 27 cm) and a similar bias (24 cm) when compared to the CS2SMOS SIT. Our results are directly applicable to the future CRISTAL mission and Copernicus programme SAR missions.

Still Arctic? - The changing Barents Sea

“…Ice thickness is controlled by external forcing, the time of onset of freezing in the region, and possible sea-ice advection from the neighboring areas such as the Nansen Basin (e.g., King et al, 2017) and the Kara Sea. In regions bordering the Barents Sea, indications for a decrease of sea-ice thickness have also been observed: during the N-ICE2015 expedition (Granskog et al, 2016;Granskog et al, 2018) Emerging techniques for ice-thickness detection through satellite-based remote sensing, such as the combinations of satellite-based altimeters (CryoSat-2 and SMOS satellite; Ricker et al, 2017), a combination of satellite-based altimeter and synthetic aperture radar (SAR) data (Karvonen et al, 2022), or thermal satellite imagery from MODIS (Rudjord et al, 2022), can be used to investigate recent changes in ice thickness, but the spatial resolution of such datasets is often coarse, and time series are too short to give an indication of recent trends. However, first results from remote sensing-based measurements are promising and timely.…”

A Meta-Analysis of Sea Ice Monitoring Using Spaceborne Polarimetric SAR: Advances in the Last Decade

“…Only four studies involved the three SAR bands at the same time. In addition, C-band SAR data were also used together with data from other sensors such as optical [39], altimeter [78], and radiometer [129] in 15 articles (see the blue circle in Fig. 7).…”

“…In addition, the dependence of the dielectric constant on ice thickness may also be influenced by other processes such as snow wetness and metamorphism, surface flooding, and inhomogeneity of ice surfaces during the melt season [2]. As a supplement, some studies (e.g., [43] and [78]) combine SAR data with other SIT products to achieve results with higher spatial and temporal resolutions than the original SIT products. In this study, the median RMSE of empirical-model-based applications is lower than that of the methods incorporating other SIT products, as shown in Fig.…”

Extrapolating ICESat-2 Derived Sea Ice Development to Sentinel-1 SAR

“…Altimetry on the other hand has very limited spatial coverage, but the variable it measures is very precise, easy to interpret and gives concrete information about the underlying ice. An existing method [7] combines Sentinel-1 and Cryosat-2 measurements of ice thickness. Their approach focuses on larger spatial scales in the region of kilometers and on situations where both measurements are available, using the SAR data to interpolate between the altimetry data.…”