There are a whole bunch of things that've happened over the last 10 milliion years. The closing of Panama is probably the biggest, but the rest of South America formed and the various lakes and large inlets were filled in or lifted up.
North America rotated to begin enclosing the Arctic, and when that's done we're back to Snowball Earth where there really isn't any circulation of water currents between the equator and the poles.
The Leftwingtards will undoubtedly object to the use of nuclear energy to "restore circulation" claiming that this will disturb the ecological balance (of that time).
Well, by then they'll be back to screaming about global cooling. Will they demand we all buy SUV’s to try to stave off the cold???