[CedarDave]

Once that water is cooled, it falls to the bottom again, and the ice can't re-form.

That doesn't make a lot of sense. Salt water freezes at a lower temperature than fresh water. With the saltier water at the bottom It would seem that the fresher water at the surface would refreeze.

[MosesKnows]

That doesn't make a lot of sense.

I tried to make it make sense.

First of all I was not aware sea water was saltier at depths.

Accepting that;
the saltier water combines with less salty water to create saltier water nearer the surface which is then unable to re-form ice.

More questions. Was the ice there as part of the winter ice and then opened up or did it remain open when the winter ice came? I'm asking because the article said the ice can’t re-form.