Ice Damage

Sailing in sea ice is a navigational hazard that must be treated with the utmost respect. Whenever possible, avoid forcing manoeuvres in severe ice conditions. When operating in ice-covered waters, maintain continuous contact with the Regional Office of the Government Icebreaking Service and icebreakers for information about the latest ice situation. It is important to notify your hull insurers in advance of trade in icy regions, as some places may give you restricted hull cover.

Comprehensive information, including traffic directions, restrictions, and weather and ice charts, is available on a number of Maritime Administrations’ web sites. Here are some useful ones:

British Admiralty:

Norwegian Mapping Authority:

Swedish Maritime Administration:

Finnish Maritime Administration:

Canadian Coast Guard:


When sailing in restricted areas, classes normally require an Ice Class to the vessel. In the list below you will find DNV-GL’s main ice classes, which may operate in channels prepared by an icebreaker and/or open water with smaller ice floes. These rules are consistent with the Finnish-Swedish ice class regulations for corresponding classes:

1A* Extremely difficult ice conditions. Ice floes of thickness 1.0 m

1A Difficult ice conditions. Ice floes of thickness 0.8 m

1B Moderately difficult ice conditions. Ice floes of thickness 0.6 m

1C Light ice conditions. Ice floes of thickness 0.4 m


In Sweden and Finland, assistance in icebreaking at sea is free of charge to fully operable vessels fulfilling current requirements. It is always up to the assisting icebreaker to decide if the assisted vessel fully complies with the requirements. If it does not comply, the vessel can be left for several days unless it is in a dangerous position. Vessel under tow by tugboat are not considered to fulfil current requirements, and do not receive any icebreaker assistance unless in distress.


Preparation to Sail in Areas with Temperature Below Freezing Point

Whenever the vessel is sailing in freezing conditions ensure that all lines are drained of freshwater and saltwater. The exception is lines that have been insulated to fulfil the requirement for emergency showers in all temperatures.


Navigating in Ice- Loss Mitigation

Patience is one of the most essential requirements when navigating in ice, since many difficult situations will resolve themselves by shifts in wind direction and/or weather. The ability to spot the difference between hard and soft ice, between passable and impassable pack ice, and to select the most suitable lead, is imperative and requires training or the employment of an ice pilot.

How to handle a ship in pack ice depends on the strength, power and manoeuvrability of the individual vessel. Damage to the vessel can be minimized with skilful ship handling, and a sensitive appreciation of the vessel’s ability to navigate in ice. The ability to turn is considerably impaired when sailing in ice. Avoid going astern; if you must, place the rudder amidships to reduce the risk of damage to the rudder, rudder post or steering gear. Move astern as slowly as possible.

If the vessel is equipped with a fixed ”skewed back” propeller, avoid any stern manoeuvre. Experience has shown that during reverse rotation, considerable stress is exerted on the tips of the blades when exposed even to thin ice, and the propellers are easily damaged.

In addition to the danger of lost stability, there might also be damage to parts such as radar aerials, radio antennas and similar equipment. If possible, protect deck equipment such as windlasses, mooring winches etc.

When berthing, be aware of the high risk of damage to the vessel’s side, especially when being pushed by tugs, due to trapped ice between the berth and vessel’s side along the quay.


Ice Accumulation

Vessels operating in high latitudes must be prepared to deal with heavy icing of the superstructure, weather deck, and exposed equipment. Under certain conditions, ice can grow rapidly and create a stability hazard, as well as an increased draft, and these situations have caused the loss of many vessels.

Ice accumulation has three causes:

  • Fog combined with freezing conditions
  • Freezing drizzle, rain, or wet snow
  • Sea spray or seawater breaking over the vessel when the air temperature is below freezing

    The first two rarely create any problems, but under certain conditions, they can very quickly create a substantial additional weight on the vessel and negatively affect the vessel’s stability. The third cause is the most common. With low temperatures and high winds and seas causing sea spray, the only way to avoid a very critical situation may be to take shelter or alter course to minimise the spray.