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Abstract In northern sea areas such as the Baltic Sea and the Arctic, especially in winter conditions, the presence of sea ice frequently necessitates icebreaker assistance operations for vessels navigating in these areas. Icebreaker escort operations are important for ensuring the safety of navigation in these harsh environments. While these operations reduce the overall system risk, studies have shown that specific navigational risks are associated also with escort operations, necessitating appropriate training and operational support for ship crew engaged in these. In this paper, the icebreaker escort operations are investigated, and a ship-following model is proposed, drawing on similarities with the car following phenomenon. This ship-following model accounts for the necessity of keeping an appropriate safety distance to avoid collision, as well as for the effects of sea ice on the operation. Its main intended use is for implementation in maritime simulators, providing a realistic environment of operational conditions for training ship crews. As a first approximation, the model accounts for the ice condition by the average ice thickness, while the safety speed constraint is relative to the vessel's ability of navigating in ice. The model parameters are calibrated using empirical data of icebreaker escort operations. Case studies are executed, showing good agreement between the simulation model and real-world operational conditions. Highlights • A ship-following model for icebreaker escort operations is proposed. • Safety distance and the effects of sea ice on the operation are accounted for. • Main intended use of the proposed model is for implementation in maritime simulators. • The model parameters are calibrated using empirical data of icebreaker escort operations. • Case studies show good agreement between the simulation model and real-world operations. [ABSTRACT FROM AUTHOR]

Icebreakers are special-purpose ships designed to operate in different ice-covered waters, either independently or during assistance of weaker ships. In the Baltic Sea, as well as elsewhere, they are essential for maintaining continuous sea transport services during wintertime. Icebreaker operations are complex, and every situation in which a vessel requires assistance is unique, due to, e.g. changing ice and weather conditions, geographical location or language proficiency of the crew on board the icebreaker or assisted vessel. The icebreaker crew has considerable freedom to adapt to each situation, yet, for safe operations, there are constraints to which the crew has to conform. The study presented in this paper aims at identifying the constraints on nautical officers on board icebreakers during operations, as well as special situations that increase cognitive load. A work domain analysis based on a group interview with nautical icebreaker officers shows the multitude of tasks performed on board icebreakers. Furthermore, it identifies constraints specific to icebreaker operations such as ice assessment and direct icebreaking, but also generic constraints such as language and communication skills. At times, safety and efficiency come into conflict, resulting in a trade-off between the two. When that happens, safety gets priority, and the operation stops until the situation has been evaluated. In addition, several situations that increase cognitive load are identified, with the common denominator that they add elements of uncertainty, e.g. severe weather and technical malfunctions. Finally, further research within the area of icebreaker operations is recommended, with a continued focus on the system constraints, and their potential for system improvement. [ABSTRACT FROM AUTHOR]

Winter navigation is a complex but common operation in the Northern Baltic Sea areas. In Finnish waters, the safety of the wintertime maritime transportation system is managed through the Finnish–Swedish winter navigation system. This system results in different operational modes of ship navigation, with vessels either navigating independently or under icebreaker assistance. A recent risk analysis indicates that during icebreaker assistance, convoys operations are among the most hazardous, with convoy collisions the most important risk events. While the accident likelihood per exposure time is rather low, accidents occur almost every winter. Even though these typically lead to less serious consequences, accidents leading to ship loss and oil pollution have occurred and may occur in the future. One aspect of ship convoy navigation in ice conditions is the distance kept between the icebreaker and the ships in the convoy, a form of the well-known ship domain concept. While operational experience naturally is a valuable source of information for decision making about the distance of navigation in convoys, systematic analyses are lacking. The aim of this paper is to investigate selected operational aspects of convoy navigation in ice conditions in the Finnish waters of the Gulf of Finland, based on data of the Automatic Identification System and sea ice hindcast data. Focus is on obtaining qualitative and quantitative knowledge concerning distances between vessels in escort and convoy operations and the respective transit speeds, conditional to ice conditions. Such empirical knowledge can support operational decision making, contributing to wintertime maritime safety. [ABSTRACT FROM AUTHOR]

Abstract: An in-situ method to observe sea ice compression in the Baltic Sea is introduced. It is known that the sea ice pressure can cause severe damage to the ships in the Baltic Sea, and therefore reliable method to observe the compression situations is needed. IceCam, which is developed to collect visual and environmental data, was installed onboard in the icebreaker Otso on the 2nd of February 2006. The camera was observing ice motion in the channel, created by the ship, taking one picture per minute. The camera was functional till the 9th of May 2006. In total 137,436 pictures with satisfactory resolution were saved. The analysis of the ice motion behind the icebreaker was done using the images. From 137,436 images the cases with clear compression situation were chosen. Also bad light conditions restricted the number of days with good data. Finally five different cases were used in the analysis. The images were corrected into coordinates, which allowed the channel width calculations. Using the channel width from two different points, relative displacement and the velocity of the relative displacement were defined. The new method gave fairly good results. We were able to locate the compression cases by the direction of the wind and ship route. The observation supported the preliminary theory of the correlation between wind and compression direction. When the wind was blowing perpendicular to the icebreaker route, sea ice compression was observed. However, when the wind and the ship route were parallel, the channel was opening. [Copyright &y& Elsevier]