Retrieval of sea-ice thickness distribution in the Sea of Okhotsk from ALOS/PALSAR backscatter data

Abstract

ABSTRACT. Although satellite data are useful for obtaining ice-thickness distribution for perennial sea ice or in stable thin-sea-ice areas, they are still largely an unresolved issue for the seasonal ice zone (SIZ). We address this problem using L-band synthetic aperture radar (SAR). In the SIZ, ice-thickness growth is closely related to deformation, so surface roughness is expected to correlate with ice thickness. L-band SAR, suitable for detecting such surface roughness, is a promising tool for obtaining thickness distribution.

An Examination of the Sea Ice Rheology for Seasonal Ice Zones Based on Ice Drift and Thickness Observations

“…The basic idea is that sea ice thickness growth in the SIZ is closely related to ridging activity (e.g., Toyota et al, 2007;Worby et al, 1996) and therefore surface roughness is expected to be a good indicator for Journal of Geophysical Research: Oceans 10.1002/2017JC013627 obtaining thickness distribution. PALSAR (L-band SAR) is useful for detecting rough surfaces because the backscatter coefficient of SAR is sensitive to the surface roughness larger than the wavelength (Massom, 2006) and the wavelength of PALSAR (0.24 m) is close to the surface roughness of deformed ice in this region (> 0.2 m; see Figure 3 of Toyota et al, 2011). This idea was supported by an air-borne Polarimetric and Interferometric Synthetic Aperture Radar (Pi-SAR) and the space-borne PALSAR evaluation experiments in the Sea of Okhotsk (Toyota et al, 2009(Toyota et al, , 2011.…”

“…Ice thickness data were obtained with a horizontal resolution of 100 m from PALSAR backscatter coefficients using an algorithm developed for the Sea of Okhotsk ice by Toyota et al (). Here we describe the concept of this algorithm and evaluate the estimated ice thickness by comparing it with the ice growth estimated with the ERA‐Interim meteorological reanalysis data.…”

“…PALSAR (L‐band SAR) is useful for detecting rough surfaces because the backscatter coefficient of SAR is sensitive to the surface roughness larger than the wavelength (Massom, ) and the wavelength of PALSAR (0.24 m) is close to the surface roughness of deformed ice in this region (> 0.2 m; see Figure of Toyota et al, ). This idea was supported by an air‐borne Polarimetric and Interferometric Synthetic Aperture Radar (Pi‐SAR) and the space‐borne PALSAR evaluation experiments in the Sea of Okhotsk (Toyota et al, ). In‐situ observations of ice thickness were used to develop a thickness retrieval method for PALSAR.…”

“…For ice concentration, a product derived from AMSR‐E 89 GHz with a grid spacing of 6.25 km, prepared by Bremen University, was used. Ice thickness was retrieved from the backscatter data of the Advanced Land Observing Satellite (ALOS)/Phased Array‐type L‐band SAR (PALSAR) with a grid spacing of 100 m, based on a field evaluation experiment being conducted in the same area (Toyota et al, ).…”

Comparison of in situ and airborne measurements of multiyear sea ice thickness with dual-frequency, polarimetric SAR observations

“…Given the strong influence of surface roughness on backscatter from FYI, this relationship has been exploited to develop thickness retrieval algorithms from single-frequency, single-polarization SAR data [7], [8]. While encouraging, these thickness retrieval algorithms cannot be directly applied to ice regimes containing multiyear ice (MYI) due to the increased influence of volume scattering from air bubbles in MYI, and the different surface roughness properties of FYI and MYI.…”