Arctic daily 1km sea ice drift product: 2018-2020, Version 2.0

The “Arctic daily 1 km sea ice drift product: 2018-2020, Version 2.0” is generated by the School of Geospatial Engineering and Science at Sun Yat-Sen University, Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai) and Key Laboratory of Comprehensive Observation of Polar Environment (Sun Yat-sen University), Ministry of Education. This product provides Arctic daily high spatial resolution (1 km) sea ice drift information over 2018-2020 in netcdf format (.nc). One netcdf file (i.e. daily sea ice drift data) consists of 4 layers, including the geographic coordinates (longitude and latitude information) and the sea ice drift speed (unit: km/d) at the x and y directions under the EPSG: 3408 coordinate system (i.e. NSIDC_EASE_Grid_North coordinate system) of each 1km grid.This product is generated by using multi-source datasets, including the medium and high spatial resolution SAR and optical data (i.e. Sentinel-1 A/B and MODIS Terra/Aqua images) and Polar Pathfinder Daily 25 km EASE-Grid Sea Ice Motion Vectors, version 4 (referred to as NSIDC-Pathfinder hereafter) provided by National Snow and Ice Data Center (NSIDC). In total, 118,359 Sentinel SAR images and 56,857 MOIDS images are used. The product process mainly includes three procedures: First, Sentinel-1 SAR images in the freezing season and MODIS images in the melting season are preprocessed with geocoding, resampling and etc. Then, the image pairs are created based on transit time and spatial overlap information. The feature tracking sea ice vectors are retrieved from the image pairs based on the A-KAZE algorithm and bad matches filtering. Finally, the merged Arctic daily sea ice drift fields are generated based on the Co-Kriging interpolation with the sea ice drift vectors as the main variable (i.e. observation field) and the NSIDC-Pathfinder as the covariable (i.e. background field). The interpolated sea ice fields are finally presented in uniform grids with a spatial resolution of 1 km.An Independent validation is conducted on this product over 2018-2020 using the IABP (International Arctic Buoy Programme) and MOSAiC (Multidisciplinary drifting Observatory for the Study of Arctic Climate) buoy observations, and a total of 35219 validation results are received. The sea ice drift velocity MAE (Mean Absolute Error) of this product is 1.25 km/d, and the angle MAE is 11.3°. Compared to the existing daily sea ice drift products (showing the speed and angle MAE around 1.5 km/d and 15°, respectively), this product shows significant improvement in accuracy.Update description: Based on Version 1.0 of the product released in 2023, Version 2.0 has undergone further methodological improvement. The earlier v1.0 product exhibited notable errors in regions where extracted sea ice drift vectors were absent. In the newly released v2.0, the multi-source merging is restricted to a 100 km buffer zone surrounding available drift vectors. Outside this buffer, the interpolated NSIDC sea ice drift fields are used to fill the gaps, thereby ensuring improved overall accuracy of the product.