A decade of sea ice concentration retrieved from sentinel-1

Arctic sea ice is fundamental to the global climate engine, modulating heat exchange between the ocean and the atmosphere and impacting large-scale oceanic and atmospheric movements. While the monitoring of sea ice concentration (SIC) from satellites has long depended on coarse-resolution passive microwave (PMW) sensors, Synthetic Aperture Radar (SAR) missions, such as Copernicus’s Sentinel-1, have emerged as complementary and fine-resolution sources of sea ice information. This study introduces the DMI-ASIP (Danish Meteorological Institute - Automated Sea Ice Products) data record; the first decade-long (2014–2024) and pan-Arctic SIC record derived from Sentinel-1 SAR imagery and provided at a high spatial resolution of 0.5 km. Compared to two well-established PMW-based SIC data records, DMI-ASIP consistently shows higher SIC and sea ice area, particularly in the marginal ice zone and during the melt season. Evaluation against an independent 2020–2022 SIC reference data record derived from optical Landsat-8 imagery indicates strong overall performance for DMI-ASIP, achieving a lower RMSE ( 8.7 % ) compared to the two PMW-based records ( 12.1 % and 13.6 % ). Furthermore, DMI-ASIP exhibits less seasonal variability in its performance than the PMW-based records. While DMI-ASIP is quantitatively closer to the reference data record, the evaluation revealed a consistent tendency for DMI-ASIP to overestimate sea ice concentrations ( + 2.5 % mean bias across the 2020–2022 evaluation period). The decade-long DMI-ASIP data record, extended by a corresponding operational near real-time product, is available through the Copernicus Marine Service. • First decade-long high-resolution Arctic sea ice concentration (SIC) record from SAR. • Higher SIC and sea ice area than PMW records, especially during the melt season. • Lower error (RMSE 8.7%) compared to PMW records (12%) when compared to a SIC reference. • Less seasonal performance variation than PMW records, especially during melt season. • Despite higher accuracy, the SAR-based record shows a positive SIC bias (+2.5%).