Operation IceTower had some initial successes. There's a 10-story 20x21 near the shore, so I got ambitious. It's all made of ice. If you dig when it's too warm in the year you "salty water" instead of ice boulders, and they also melt in transit. So my ice tower 100 squares in-shore has to rely on the creek. So now I am digging a 50x50 pit, and filling it with the biggest tower dwarvenly possible can. First priority is to get the five under-sea-ever stories done so that it is water-tight, because the freeze/unfreeze cycle will destroy many constructions (especially bridges). Others (such as stairs) disappear, but when you re-mine out the square they come back.
However there are two unexpected problems:
1) I ran out of booze. It's a freezing biome, and there were 130ish of the little twerps, so they're dying of thirst. Solution: work like the dickens until the great unfreezing for the purpose of Dwarven science, then save-scum and do something about the booze sit before half my starting seven die. I may be forced to interact with the caverns.
2) I just got invaded by a Wereass. This is a nice change for my militia, whose previous victims were a giant crab and a handful of kobolds, but it will screw up the timeline.
EDIT Down to 20 guys, and still no thaw, but even with the death of the entire labor force I gor a good 35% done. So if I figure out the water situation this should be very viable.