Ice conditions affecting passage of Polish vessels convoy though the NSR in 1956. Long-term ice forecasts and passage strategies.

The goal of the study was to examine ice cover conditions that accompanied the passage of convoy of seven Polish vessels from Europe to the Far East in year 1956, which initiated an international commercial shipping transit. Several different sources of information on the state of ice cover in the Arctic were used in this study. Ice conditions (decisive for ability of a merchant vessel or icebreaker to cross the route) during the following navigational seasons in most of the NSR areas showed extremely divergent results - from the most favorable to the most difficult and vice versa. Existing in years 1940-1957 ice cover conditions and shipbuilding technologies did not guarantee a successful transit passage in one navigation season. The Soviet Union used icebreakers that were not able to lead vessels in heavy ice conditions that occurred in 1950s. The NSR Administration used passive strategy -- waiting for improvement of ice conditions - instead of forcing heavy ice. Passive strategy of navigation through the NSR included wintering and continuation of passage next year when ice conditions improved. Annual variability of ice conditions approximated by third degree polynomial line showed trends well. However, the high annual anomalies of ice conditions in relation to trend line did not allow for effective forecasts on particular sections of the NSR in next navigation season. [ABSTRACT FROM AUTHOR]

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