State Key Laboratory of Coastal and Offshore Engineering;
Dalian University of Technology;
Dalian 116024;
China;
MNR Key Laboratory for Polar Science;
Polar Research Institute of China;
Shanghai 200136;
China;
Institute of Atmospheric and Earth Sciences;
University of Helsinki;
Helsinki 00014;
Finland;
sea ice concentration; passive microwave remote sensing; ship-based visual observations; Arctic navigation; summer;