Robot Made of Ice Can Repair and Rebuild Itself

More specifically, imagine ships sailing around the Arctic circle just before the water freezes in winter, dropping sawdust (or newspaper for "super Pykrete") in their wake.

Since sawdust comes from trees, it's sequestered carbon. Once you put it in the water, it's not going to burn down and release its carbon like a tree in Australia or California might.

Since it floats, it should stay near the top of the water until the water freezes. Pack ice with sawdust frozen in it will last longer and reflect the sun's light back for a longer period of the year. There's a risk of the albedo being affected negatively--perhaps using light-colored wood for the sawdust would help with this.

Hopefully, even after the Pykrete melted, the sawdust would stay in the ocean near the surface, and re-freeze next year so you get Pykrete every year. (A potential downside here is that the sawdust could be difficult to remove if we ever realized this plan was backfiring somehow. Maybe we'd prefer some sort of sawdust which eventually sinks for that reason.)

Another idea is to bioengineer some kind of organism which reproduces in the Arctic ocean and changes the consistency of the water so that when it freezes it behaves more like Pykrete. Perhaps some kind of algal bloom (apparently you can trigger algal blooms by seeding water with iron?) To be safe, before releasing this organism into the environment, we could bioengineer some other organism which feeds on this and nothing else, so we have a way to reverse the experiment if it goes wrong.

Hey, I don't think it is much more harebrained than other geoengineering ideas I have seen floated :)