The North Atlantic has plenty of ice bergs. You can go to a cluster of them and destroy them all to grind this achievement, or you can just hit them as you progress through the story. There's a good use for these. If you destroy them in combat, you can stun and damage enemy ships close to them with the waves they generate. Just destroy ice bergs that come your way while you do missions in the North Atlantic. This achievement isn't that hard to get. There are a lot of ice bergs, so if you deliberately farm this achievement, and destroy them in the story, you'll get it soon.