The world is all messed up and the effects of global warming are everywhere except (for the most part) Antarctica. The combination of the circumpolar current and the winds that feed it (and feed off of it) insulates it. Global warming is unstoppable but it will proceed in drastic discrete stages with Antarctic melting last. Why not do it altogether for a smoother transition? What would it take to slow down the current in the
Drake passage? (800 km long and 4000 meters deep).. I guess trawler
nets are out of the question. But how about vertical tethered carbon
fiber ropes? Fiber slightly lighter than water (or with a balloon on
top) and of course an anchor on bottom. Or it could be steel rope, anchor on the bottom, buoy on top. And it does not need to reach the top of the water (4 km is a lot!) They would swing back and
forth a little in the current The idea is to slow the momentum
slightly, create eddy currents and warm the water slightly that
comes from the south pacific to the south Atlantic. I think as a
species, we need to let the antarctic ice sheet melt and get on with our
migration north and south. Slowing the current a little bit might be
enough to break the dynamic of the circumpolar winds and circumpolar
current. They feed off each other. It might be better to start on the
Antarctic side. Just do the cold half. Even a remote fraction of a degree of warming, and the slightest slowing of the current would have an effect. And with the slight warming, on the cold side, the winds that drive the current would be slightly abated too. So 400 km of (say 1000 meter) wire ropes with anchor on bottom and buoy on top. What would it cost? How long before it slowed the flow? Would it warm Antarctica or would it bring more moisture (to the driest continent on earth) and lower sea levels? And if it works too well or too badly, we can always "pop" the buoys and drop the ropes to the sea bottom. Any thoughts? I think this is counter intuitive but it would also be the cheapest geo-engineering project going. 
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