3.2.2. Icebreakers assistance
Icebreaker assistance operations are performed each winter. The number of operations depends on the ice-prevailing conditions in the operative area for which the icebreakers have been designated. During winter 2010–2011 (a winter categorized as severe by the Baltic Icebreaking Management organization), about 10,750 vessels were assisted by icebreakers in different areas of the Baltic Sea. The Gulf of Finland and the Bay of Bothnia constitute the areas in which most of these operations were performed, 4604 and 4277 operations, respectively (BIM, 2011). Icebreaker assistance is commonly linked to five practical operations (Rosenblad, 2007):
Escorting: an icebreaker is escorting when it breaks an ice channel and the assisted ship follows the icebreaker at a recommended distance.
Breaking a ship loose: an icebreaker is breaking a ship loose (or cutting loose) when it passes a ship that is stuck in ice from a close distance and breaks the ice beside and in front of the assisted ship, thus releasing it from ice pressure.
Convoy: the operation is similar to escorting but in this case there are several ships following the icebreaker. The distances between the convoy vessels should be long enough to allow the following vessels to stop if the ship in front is stuck.
Double convoy: two icebreakers are involved in a double convoy operation when a second icebreaker travels ahead or behind and slightly to the side of the first icebreaker in a convoy operation. This occurs when the vessel(s) in the convoy has a larger breadth than the icebreakers.
Towing: an operation occurring when a ship cannot follow an icebreaker because the ice pressure makes the channel close quickly, the channel has too much slush ice, and/or the assisted ship does not perform appropriately in ice. An icebreaker may be towing one vessel while simultaneously leading a convoy.