While the Arctic is warming at twice the rate of the rest of the planet, ice conditions there as well as on northern seas and lakes will require icebreakers for many years to come. The same will be true for the high latitudes of the Southern Hemisphere.
The icebreaking ship has basically a very strong hull with the largest possible engines to power her through ice. Historically her primary function has been to keep shipping lanes open for as long as possible. In recent times these ships have been increasingly needed, however, as platforms for polar research activities and resource development—all functions often at odds with the vessels' primary mission.
Development of the seagoing steam engine and screw propulsion in the mid-1800s made possible the first practical icebreakers. The ships worked by virtue of brute force pushing against or ramming the ice. This limited the thickness of ice that could be broken; hitting it head on is where ice is strongest. The substance is relatively weak if it is pushed down or lifted up.