Why does my root beer float foam when the ice cream is added?

Question

Why do warm carbinated beverages offgas when ice (or cold ice cream) is added. Isn't this contrary to the gas solubility laws? Shouldn't the carbon dioxide be more soluble in the liquid as it cools down?

Answer 1

The root beer begins off gassing as soon as it is no longer under pressure. The ice/ ice cream simply provides a good surface area for the bubbles to form more quickly.

Answer 2

I would guess that when ice cream is added, some of the sugar and cream dissolves in the liquid. This displaces some of the dissolved gas, since the liquid is already saturated.