That’s a new geoengineering idea I haven’t seen, designed for a custom problem. I would put such a thing in the category of megastructures, even the simplest version of a barrier. I have to wonder how much additional emissions we’d have just from the efforts. It’s always better to sharply reduce existing emissions and deal with the problems that will cause than to pretend we can keep going and find a magic remedy. Also, like any other geoengineering, once in place it must be maintained to keep the continuing warming rate down, otherwise things would spike. In this case a curtain that suddenly drops or deteriorates from lack of maintenance means the water temperatures and flow that was held back suddenly is present in greater amounts and differences. Carry that picture to its conclusion.

We will geoengineer where we can when things get desperate. It’ll be the last ditch effort to preserve the 1% way of life at the cost of everything else, and something will go wrong eventually. Murphy was an optimist.