Methodology:

The dataset contains the FSD data derived from the GFL imagery at the three fixed locations across the Arctic Ocean. The GFL imagery is 1-m resolution declassified intelligence satellite imagery (National Technical Means), later released to the public by USGS (United States Geological Survey). The imagery data have been obtained from the USGS GFL website. For the production of this dataset, we used the GFL imagery data acquired at the three fiducial sites - Chukchi Sea (70°N and 170°W), East Siberian Sea (82°N and 150°E), and Fram Strait (84.9°N and 0.5°E). The imagery data at the fiducial sites are available as early as 2000 until 2014, providing a long-term collection of the data. This FSD dataset contains the pre-ponding period (i.e., ponding on the ice is not visible in the imagery). Total 41 images were analysed to derive the FSD using the algorithm described in Hwang et al. (2017). The original imagery is available at 1-m resolution but reduced to the 2-m resolution ("res2m") for the FSD retrieval.

The FSD dataset was produced by using the algorithms as described in Hwang et al. (2017), which were implemented in MATLAB.

Data quality:

The data quality was checked through manual inspections by the data producer, but the absolute accuracy of the data is unknown due to lack of ground-truth data (see Hwang et al., 2017).