4. Selected Dangerous Hydrological Phenomena and Voyage Planning

This chapter is related to the selected dangerous phenomena on the NSR which affect safe voyage of the vessel of any ice/polar class. The first issue discussed in the chapter was the question of the definition of ice massifs and explained what means “disappearance” or “total disappearance” of ice massifs. This term does not mean, against appearances, that there are no threats to ships in the regions of the occurrence of ice massifs. General maps of ice massifs location were developed for winter and summer season. The phenomenon of extremely fast ice drift, also known as “ice river”, was widely discussed. This phenomenon is not well known. Its general locations along the whole NSR were presented. Mathematical relations between speed of extreme ice drift, sea-level gradient, length and width of “ice river” trough were developed. Next, this chapter presents an assessment of possibility of initial route planning based on Russian long-term forecasts of ice navigation conditions on the NSR covering time up to 2–5 months ahead. Thematic scope of these forecasts includes dates of occurrence of particular types of ice navigation, area covered with close ice (ice massifs) and anomalies of ice massifs in the selected NSR regions, date of ice cover growing and date of reaching 25–30 cm thickness of young ice in selected locations. Presented approximate predictability of forecasts of types of ice navigation conditions for all the seven NSR seas. It was found that probability of correct long-term forecasts of types of ice navigation conditions is much lower than for the beginning and end dates of ice-free zone occurrence. Assumed that areas of any form of ice should be avoided if it is possible and if it is not associated with excessive voyage time elongation. Next assumption was that the basis for planning navigation in ice, i.e. choosing and developing a voyage route, is “to avoid melting of ice, which vessel cannot overcome alone”. It has been assumed for vessels without ice strengthening that term “ice that cannot be defeated by the ship” should be equal with concept of “any form of ice” except “the first form of ice”. The criterion of “safe and the most economically efficient route designation of the planned voyage” was adopted as the basis for planning route. It has been noticed that the lightest conditions for ice navigation are “ice-free” conditions.