That's a really good question. Maybe we could pump it to a colder area of Antarctica? Or pump a corresponding amount of ocean water to a cold area of Antarctica.
Surface area of Earth = 510 million km^2 = 5.10e14 m^2.
~70% is water, so 3.57e14 m^2.
Multiply that by 3mm (3e-3 m) = 1.07e12 m^3.
1.07 trillion tonnes of water. Per year.
Or 33,907 tonnes per second!
Actually the Hoover dam streams 2000 tons per second [1]. So we may not be far off!
Basically build 15 Hoover dams worth of nuclear plants in Antarctica and their plumbing.
Expensive? Yes. But also quite doable especially compared to cost of losing coastal cities.
1. https://www.nps.gov/nr/travel/ReclamationDamsIrrigationProje...
It would require a lot of energy, but all remedies to climate change require that.
Where does all the energy go if it does not go into raising the temperature?
The Gulf Stream does exactly what is suggestion, moving massive amounts of warm water north and it's effect on winter temperatures in Western Europe is massive.