Why do my ice cubes do this?

Factual Questions
1

For the first time in 32 years I am observing an unusual occurence in my ice cube trays. My ice cubes are developing reverse icicles (for lack of a better term) Thin verticle spikes of frozen water protrude from my typically docile ice cube tray.

Only one explanation occurs to me: My freezer is very cold and as I make fresh ice, the water freezes rapidly and cracks, causing extremely cold water to shoot skyward, instantly freezing into the abovementioned formations.

Any ideas?

2

I think you have it pegged.

The thing that makes a difference is bubbles on the surface. These will be weak spots. The surface hardens, the center expands, and the bubble points provide an escape valve.

3

We’ve discussed this before in this thread