As Salty said, the Arctic region is a sea covered by ice floes that need breaking. Antarctica is a continent covered by ice, which calves bergs. Icebreakers are not much use against bergs.
Only in certain places, the Weddell Sea for instance, are breakable ice floes found. There are mini-bergs, solitary hunks of ice that can damage a hull that has not been strengthened to withstand impact with them.