Alterations of summer ice conditions within eastern part of the Northern Sea Throughway

The article is considered methodology and results of computer processing of vector ice maps of the AARI archive for the period 1997-2018. The charts were produced by processing of Earth's remote sensing data. There were analyzed inter-annual variability of navigation conditions along two routes between the Sabetta Port (the Yamal Peninsula, Russia) and the Bering Strait during September that is annual period of the most light ice conditions. As the results of the processing there were obtained long-standing series of total lengths of the routes legs within free water, within close floating ice with concentration more than six tenths, and such integrated ice index as conditional lengths of the routes within compact floating ice with 10 tenths concentration. The series belong ten-days periods (decades) during September. The series were tested for the existence of trends by the method of integral curves, and then were examined for heterogeneity using Wilcoxon-Mann-Whitney and Siegel-Tukey rank non-parametric criteria. We received the following results: the total lengths of the routes legs within free water increased for the period of 1997-2018 years, ones within close floating ice and conditional lengths of the routes within compact floating ice decreased. There is some improvement of the ice conditions.