But the hoover dam just drops the water, what, a few hundred meters? We'd need to transport the water many km from the oceans to the middle of the antarctic continent, and lift it a couple km, to the tops of the glacier. So it's way more than 15 hoover dams.
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...