If you make a sturdy frame over the pond, or part of it, stretch 6mil plastic (better still two layers) over the area you may find the 'cold frame' may salvage the situation. Some folk nickname the technique 'solar cover' for ponds

When the sun makes the temperature within rise you can get quite a thaw going. Through the night, the cold frame will contribute by retaing ground warmth

You may well find the entire area enclosed completely thaws out in a couple of days and ice stops forming...

Regards, andy
http://www.members.aol.com/abdavisnc/swglist.html