Comparative analysis of the ice coverage in the Bering sea according to the Sea Ice Index and Masie data

Abstract

This paper presents a comparative analysis of the ice cover of the Bering Sea. The analysis was performed according to the National Snow & Ice Data Center (NSIDC) using NASA algorithms Team (Sea Ice Index) and Near-Real-Time Passive Microwave/Visible Data Sharing DMSP SSMIS Daily Polar gridded Sea Ice Concentrations and Sea Ice Concentrations from Nimbus-7 SMMR and DMSP SSM/I-SSMIS Passive Microwave Data (MASIE-NH). The absolute and relative difference of the ice cover values were calculated using the algorithms Sea Ice Index and MASIE-NH with daily discreteness for 14 ice seasons from 2006 to 2020. Despite the fact that the spatial resolutions of the data of the algorithms under consideration and the quantitative criteria for the condition for classifying a pixel as pure water or ice extent differed (the side of the pixel was 25 and 4 km, identification was 15 and 40 %, respectively), the curves of the average seasonal variation of the ice cover were in phase and that was confirmed by the high value of the correlation coefficient (0.92). It was determined that the difference in ice cover values were not critical and were within the calculation limits, which allowed using data from both sources without calculating correction factors. Sea Data Ice Index data should be appropriate for long-term analysis of inter-seasonal variability, since data series of observations with daily discreteness have been available since 1978. It was concluded that the use of both sources would be quite acceptable in the analysis of intra-seasonal fluctuations. A characteristic feature of Sea Ice Index was noted—the presence of ice throughout the warm season. Although according to literary sources, such a phenomenon in the Bering Sea was typical only for severe types of winters. That was probably due to the technical difficulties in identifying the ice extent using passive microwave sounding methods.