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MMM SEMINAR NCAR

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Ice Cube Spikes

Charles Knight

NCAR

“Ice cube spikes” are spike-like ice projections from the tops of ice cubes, several mm in diameter and up to several cm long. While quite rare, they are a frequent subject of questions in popular science. They have not been studied systematically until very recently. Two recent papers confirm the “Bally-Dorsey hypothesis,” that they form as the ice cube freezes from the outside in, squeezing water out of a hole in the ice shell, up the center of the hollow spike, freezing continually at its tip. Actually, this was obvious to start with, and can be confirmed simply by watching the spikes grow. That might be thought to be the end of the story.

Here, however, it’s the start of the story. Why are they rare? What are the other responses to the 10% expansion during the freezing of an ice cube, and what selects between them and spike formation? Some of the answers were fairly easy to find, but were unexpected. (Partial answers, rather; like many topics research topics motivated by curiosity, this one leads farther than one is inclined to follow. I followed it until the curiosity embodied in the initial questions was satisfied).

Thursday, 12 August 2004, 3:30pm

Refreshments 3:15pm

NCAR - Foothills Laboratory

3450 Mitchell Lane

Bldg. 2, Main Auditorium (Room 1022)