ИСТИНА

The ice-free period detection uncertainties are reviewed using satellite-derived sea ice concentration data. A case study of Marresalya, western Yamal Peninsula, the Kara Sea is considered. The ice-free period characteristics, obtained from four satellite sea ice concentration datasets with different spatial resolution and algorithms, were tested for sensitivity to averaging radius (range from 15 km to 50 km with 5 km lag) and were compared with observations from Marresalya station. We found, that the accuracy of ice-free period characteristics estimations (in terms of root mean square errors and linear tendencies) could be improved by averaging sea ice concentration data in radius 25-40 km. It was also shown, that the NSIDC datasets provides the best estimations despite the coarse spatial resolution. High-resolution data (< 10 km) include too much interannual noises in the nearshore pixel time series. It complicates ice-free period characteristics estimations.