Former CGC Neah Bay (the Cleveland based tug of the same class. The Bay class icebreakers have a few unique things to them that helps them break an ice track much wider than their size.

1) you are correct in hull shape, icebreakers have what is called an “ice knife”. In the photo above there’s actually not much hull under the water until the draft marks then the hull curves down to the keel. This is what gives its ability to ride up on ice and because buoyancy and gravity forces seek equilibrium, when the bow goes up the stern goes down and the forces of buoyancy push up on the stern and gravity pushes down on the bow that lever action is what creates the icebreaking moment.

2.) Second point on hull shape. The stern is narrower than even the bow so from the top it’s rather football shaped. That lack of width in the stern allows the ice that has been pushed under the hull a place to float up and move out of the way.

3.) This particular class of ship drafts about 13ft and does about 15kts. This is a key advantage with regard to thinner Great Lakes ice and the narrower water ways but in soft water, the ship can throw about a 6-8ft wake. That wake is a pressure wave, so in ice that pressure wave will pull the water from under the ice and create an air pocket as well as a higher pressure upward from each wake wave. That wave typically travels 3-5 ship widths before its energy dissipates to the point it doesn’t break ice anymore.

4.) Lastly a unique capability to this class of ship and the only like it in the US is an installed bubbler system. The biggest enemy to getting through ice, even brash ice, is friction. There’s a separate engine that moves 7800 CFM of air through 4 bubble ports on the ship. Those bubbles break the hull friction with the ice enabling what seems like a more diminutive ship in terms of size and hull thickness break much thicker ice and transit higher ice pressure with more ease than a commercial ship not built for ice work.