“Why? These ice shelfs are already in the ocean, aren’t they? “
If you had researched before posting you would not have made this post!
Actually I did research it - and I made sure to ask the question as well, so as not to claim specialist knowledge of it. If YOU care to research the Ross Ice Shelf, you will find the definition is: "Ice shelves are thick plates of ice, formed continuously by glaciers, that float atop an ocean."
Now, do you want to offer information that contradict that in a useful way? Or are you just about being snarky?