Say the temperature swings between 31° and 33°F. Which part of an icicle has the most recent water?

Factual Questions
1

See subject. I’ve been thinking about this off and on all night, and I keep coming up with different answers.

So far I’ve thought that following variables must be figured in: amount of time at 31°, 32°, and 33°; wind speed; length of icicle; surface tension; condensation; and rates of melting and freezing in air and on ice.

2

The outside.

3

This reminds me about the one with the 10x10x10 cube, with a lightbulb in the center of the top. When the light is turned on, which part of the cube gets light first? last? When the light is turned off, which part of the cube gets dark first? last?