Sue, you'd be amazed at how fast the ice melts once the system is turned on.
I did the same thing that he did a few years ago, installing a system thru the ice. But, the ice was only 6", not a foot. I left the hose on top of the ice and it sank when everything thawed in the Spring.
The hole in the ice went from 2' square to almost 20' diameter in a day.