Weird Instant Slush Phenomenon

This evening when I poured myself a pepsi over ice, I noticed the weirdest thing.  As I poured, the liquid, once it hit the ice cubes, immediately turned to pepsi slush.  I'd never seen that happen before, but I think I know what happened.  Where we keep the soda in the refrigerator is a compartment that has a cooling vent that blows cold air into it. I imagine this is there because things on the door of a fridge don't get as cold as those in the center and back of the fridge.  For some reason, and perhaps it has to do with the changing weather and drop in humidity, the soda has been getting colder than it had been.  Perhaps it's temperature is below freezing--the CO2, I think, lowers the freezing point of a liquid.  So when I poured the really cold liquid over the ice, it instantly began to freeze.  I thought I was going mad, but I searched the web and found a really cool video that shows this phenomenon.  This video shows a more drastic version of what I experienced.  Have a look:

Supercooling Experiment #4 - Instant Slush - The top video clips of the week are here