Abstract
Abstract. A method of simultaneously estimating snow depth and sea ice thickness using satellite-based freeboard measurements over the Arctic Ocean during winter was proposed. The ratio of snow depth to ice thickness (referred to as α) was defined and used in constraining the conversion from the freeboard to ice thickness in satellite altimetry without prior knowledge of snow depth. Then α was empirically determined using the ratio of temperature difference of the snow layer to the difference of the ice layer to allow the determination of α from satellite-derived snow surface temperature and snow–ice interface temperature. The proposed method was evaluated against NASA's Operation IceBridge measurements, and results indicated that the algorithm adequately retrieves snow depth and ice thickness simultaneously; retrieved ice thickness was found to be better than the methods relying on the use of snow depth climatology as input in terms of mean bias. The application of the proposed method to CryoSat-2 radar freeboard measurements yields similar results. In conclusion, the developed α-based method has the capacity to derive ice thickness and snow depth without relying on the snow depth information as input for the buoyancy equation or the radar penetration correction for converting freeboard to ice thickness.
Highlights
Satellite altimeters have been used to estimate sea ice thickness for nearly 2 decades (Laxon et al, 2003, 2013; Kwok et al, 2009)
We found that this slope pattern is of a consistent nature even for different datasets; two different datasets covering various ranges of Tsnow / Tice show similar distributions along the two different slopes
We examine how the use of MW99 for retrieving sea ice thickness from ICESat and CS2 measurements compares with results from our simultaneous method
Summary
Satellite altimeters have been used to estimate sea ice thickness for nearly 2 decades (Laxon et al, 2003, 2013; Kwok et al, 2009). There are two types of satellite altimeters measuring different sea ice freeboards. (1) Lidar altimeters such as NASA’s ICESat (Zwally et al, 2002) and ICESat-2 (Markus et al, 2017) missions measure the total freeboard (Ft), which is the height from the sea surface in leads to the snow surface. (2) Radar altimeters such as ESA’s CryoSat-2 (CS2) (Wingham et al, 2006) measure the radar freeboard (Fr), which is the difference in the radar ranging between the sea surface and the radar scattering horizon. By applying two correction terms regarding the wave propagation speed change in the snow layer (Fc) and displacement of the scattering horizon from the ice surface (Fp), the radar freeboard is converted to the ice freeboard (Fi), which is the height from the sea surface to the snow–ice interface (Fi).
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