Why is it that when you first fill a glass with soda (ice included), it fizzes like crazy (making you wait until it settles to add more soda) but when you fill the same glass a second time there is hardly, if any, fizz?
The glass was warm the first time. The ice cooled the glass and the soda.
The ice is very rough at first, and provides lots of nucleation sites for bubbles to form. Additionally, the ice you pull out of the freezer is colder than the freezing point for the pop. When you first add pop, some of it freezes onto the ice cubes, and may do so in a way that is rough, and makes a lot of nucleation sites. After some time, the ice surface melts to a more or less smooth surface, providing fewer nucleation sites. You cold test this by putting the used ice cubes in a new glass, and pouring new pop in. The used ice cubes in my experiment above will be right at the freezing point, so the new pop won’t freeze to them, and they will stay smooth.