It's as though a compulsive recycler used them once and put them back for another round. Your ice cubes have been sublimating. . Sublimation is no mean feat. It's not exactly against the laws of chemistry, but it's not the normal progression. Set an ice cube on the counter and you'll see how an obedient substance warms up.
Gravity drags the loosened molecules into a pool around the ice.
The molecules, getting warmer still, speed up enough to break free and disperse in the air. When you add wind, that allows more of the gaseous molecules to leave the mother ship. In your freezer, the extra wind is a rather recent innovation designed to combat normal household humidity. Bits of water vapor are always invading iceboxes. Each time you open the door, damp air rushes in.