Icebreakers break ice by using momentum and power to push their bow up on the ice. The ice is pushed down by the weight of the ship which causes the ice to break off in chunks. The broken ice is then pushed out of the way by the hull of the icebreaker as it proceeds forward.
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This diagram shows how the sloping bow of the
icebreaker rides up onto the ice, forcing it to break off
in chunks. Icebreakers are specially designed for this and have sloping bows, heavy displacement (weight) for their size, and lots of power. In addition, they are specially reinforced to handle the force of the ship hitting the ice at speed. |
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The U.S. Coast Guard's Polar Class Icebreakers (POLAR
SEA and POLAR STAR) are the world's most powerful
non-nuclear icebreakers. They are heavy for their length
(13,000 tons & 399 feet/121.6 meters long) and have
lots of power; 18,000 horsepower in diesel-electric
operation and 75,000 horsepower in gas-turbine mode. The
ship's frames (skeleton) are designed to absorb the shock
of hitting the ice and the skin of the ship along the
icebelt is 1-3/4 inch thick steel. The hull is made of a
special steel designed to operate in the ice in cold
temperatures. The Polar Class Icebreakers are capable of
breaking through 6 foot thick ice at a continuous speed
of 3 knots. CDR Mike Powers looking at the bow of POLAR SEA. Note the angle of the bow near the ice. |
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The following sequence of photographs are of the
Russian Icebreaker YAMAL. The photos were taken during
the 1994 Arctic Ocean Section Expedition by CDR Mike
Powers. As YAMAL charges ahead, its sloping bow will allow the icebreaker to rise up on the ice, increasing the downward force on the ice. |
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You can see how the bow rises up onto the ice as the YAMAL proceeds ahead. As it does, more and more of the icebreakers' weight is placed on the ice under the bow, causing it to break. |
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As the ice under the bow breaks downward, the bow falls to its normal level and the process begins again. |
The YAMAL is nuclear powered and develops 75,000 horsepower in a steam-electric propulsion plant. She is larger than the U.S. Polar Class and is able to break 7 feet of ice continuously. YAMAL and her sister ships are the most powerful icebreakers in the world, but they require cold water to cool their reactors. Since the ocean at the equator is warm, these icebreakers are unable to transit to Antarctica.