Methodology:

The FSD data were derived from multi-satellite imagery data, including MEDEA, TerraSAR-X/TanDEM-X and WorldView-3. For MEDEA images, the selected images were cropped to remove the areas with clouds and missing data. The cropped images were then used to derive the FSD. For TerraSAR-X/TanDEM-X images, the raw data (Level 1B products) were acquired from DLR (under TSX SSS project hwang_OCE3757). The images were applied to ellipsoid correction (range doppler) and speckle filter (median) and converted to GeoTIFF files. Those GeoTIFF files were used to derive the FSD. For WorldView-3, panchromatic images were used to derive the FSD. The floe size distribution was derived from those images using the algorithm described in Hwang et al. (2017).

Data collection:

Characteristics of satellite imagery data used to derive the FSD data are described below.

MEDEA: 1-m resolution visible (panchromatic) satellite imagery from the USGS Global Fiducials Library (GFL) (https://gfl.usgs.gov), declassified by the MEDEA group.

TerraSAR-X or TanDEM-X: X-band satellites operated by the German Aerospace Centre (DLR, www.dlr.de). For the FSD retrieval, three image mode data - Spotlight (SL), StripMap (SM) and ScanSAR (SC) were used (for the details of the image modes, see https://earth.esa.int/eogateway/catalog/terrasar-x-esa-archive ).

WorldView-3: A commercial satellite by Digital Globe (https://www.digitalglobe.com). The FSD data was derived from a panchromatic image of WorldView-3 (WV3).

Data quality:

The data quality was checked by manual inspection for each imagery data. It should be noted that some of the small floes can be erroneous due to noises or internal variations within the images. However, no minimum threshold for the smallest detectable floes was set for this dataset (i.e., the smallest floe equals one image pixel). This is to provide flexibility for the users to select the minimum threshold for the smallest detectable floes. For instance, in our observational study, the minimum threshold was set to be 5 m for MEDEA/WV images (i.e., the floes small than 5 m in diameter were discarded from the analysis) and 15 m for TerraSAR-X images (i.e., the floes small than 15 m in diameter were discarded from the analysis).