GNSS L-Band signals are known for their particular properties related to water in its liquid and solid state. They easily penetrate dry snow, however, they are almost entirely reflected at the sea surface. Therefore the reflected signals can be used to characterize sea ice, which has properties of solid and liquid water in parallel. The horizontal sea ice structure and its thickness in the Polar regions is a key parameter for climate change characterization.
Measurements of the reflected GNSS signal's amplitude allow to retrieve the sea ice concentration and potentially its structure, especially water content, salinity and roughness. The Doppler shift resolution of the reflected signal is expected to additionally provide information on the sea ice thickness.
The ArGID project explored ice observations from a GNSS reflectometry setup by GFZ during dedicated ship expeditions with the Norwegian research vessel “R/V Lance” or the German Icebreaker “Polarstern” during the MOSAiC campaign. The concept of measurements and the anticipated objectives in the ArGID project with the “Lance” are shown in Fig. 1.
The power of the reflection peaks show significant features related to sea ice, see Fig. 2.
High ice concentration periods (B,C), a calm open water period (D) and the high sea state period (A) differ by peak power distribution. Highest power refers to D, significantly reduced power refers to B,C and lowest power (with higher noise, not shown) indicates period A.
References
Semmling, M., Wickert, J., Kreb, F., Hoque, M.M., Divine, D.V., Gerland, S., Spreen, G.: Sea-Ice Permittivity Derived from GNSS Reflection Profiles: Results of the MOSAiC Expedition, IEEE Transactions on Geoscience and Remote Sensing, 60, 36, doi: 10.1109/TGRS.2021.3121993, 2022.
Semmling, M., Rösel, A., Divine, D. V., Gerland, S., Stienne, G., Reboul, S., Ludwig, M., Wickert, J., Schuh, H.: Sea-Ice Concentration Derived From GNSS Reflection Measurements in Fram Strait. - IEEE Transactions on Geoscience and Remote Sensing, 57, 12, 10350-10361, https://doi.org/10.1109/TGRS.2019.2933911, 2019.
