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Summary of Working Paper No. 39-1996

I. 1. 8: Influence of Ice Compression on Feasible Navigation on the NSR

By Torsten Heideman, Kværner Masa-Yards Inc., Helsinki, Finland.

Ice compression is a phenomenon that has a drastic influence on the feasibility of Arctic operations. Experience has shown that today, even the most powerful icebreakers will become immobilised during events of severe ice compression. This means that the influence of compression must be taken into account when calculations regarding NSR shipping operations are performed.

The report is a survey of the present status of Russian knowledge of ice compression along the NSR. The Arctic and Antarctic Research Institute in St. Petersburg was contracted to go through their databases and reports and compile a report. In the INSROP report we have extracted results of major interest from a navigational point of view from the Russian report.

The first part of the report describes briefly the different forms of ice compression and the factors that influence it. The second part describes the present means to identify ice compression. The third and last part is a review of existing data on the occurrence of ice compression along the NSR.

Ice compression is normally divided into categories, based on their origins. The Russian practice is to divide the ice compression as follows:

INSROP00090000.gif dynamic ice compression due to wind, tide and current

INSROP00090000.gif static ice compression due to thermal expansion

The most common method to identify ice compression is to study the behaviour of the channel behind the ship and the interaction between the ice and the hull of the ship.

Wind is by far the most important cause of ice compression. In almost 90% of the cases of severe ice compression, that is more than 2 balls, the direction of the wind coincides with that of the ice movement.

Based on long term Russian statistics the probability of encountering ice compression is claimed to be in the order of 60%. However, this figure is not undisputed since it is not supported by observations from numerous Arctic voyages undertaken by KMY.

The present means of observing ice compression are briefly presented and found inadequate. In the Russian database the ice compression is expressed with the help of a 0-3 ball scale. It is not possible to directly link this ball scale to the actual stresses in the ice field. The obvious continuation to this investigation is to find a way to relate the readings of the ball scale to physically defined measures, such as stresses in the ice field or forces exerted on ships and structures. Model tests in ice are considered the most cost efficient way to proceed.