You need a mirage with fire abilities in order to melt ice obstacles.
Do you have, for example, a Black Nakk? I think that's the early game mirage which will have the 'sizzle' ability enabling you to melt objects.
Bombs, Ifrit (and the diminutive version Fritt, etc), and a few other mirages also have this ability, but Black Nakk might be the local mirage which you should have access to at this stage in the game. If you can't catch it in Icicle Ridge itself then it might be one of the earlier areas you will have visited already.
Also if you go back to the cave where you had to decide between Ifrit, Rahmu, and Shiva there is a secret area in there pretty sure you can access it though forget exactly how atm, but you go there and you can capture the mini forms of the other two there as well as the one you choose.