It goes hand in hand with ice shelves calving. The weight of the ice forces the shelf farther and farther out to sea. The ice flows. Eventually simple strength of materials tell us that the shelf is going to break off. I’m always amazed at the doomsayers who seem to think it should continue to the equator.
Ice on land is different but the same. The sheer weight forces it to flow. Eventually another force, temperature, is going to prevent the ice from covering the globe. It might be interesting for scientists to study what affect the increase in freshwater runoff has on climate.
1960's-era "World Book" encyclopedias contain references to ice floes the size of Delaware; giant floes/bergs are by no means a modern phenomenon.