That would be a LOT of weight removed from the land, and the land would RISE up from the sea level with all that mass removed.
Yes, the mechanism is called "isostatic rebound." It's happening right now in the Great Lakes region and other places around the world where former vast ice sheets have retreated due to natural "global warming." But it's a very slow process happening over thousands of years. It would be barely measurable in a normal human lifetime.