I came across this while browsing [1]. That thread has a lot of interesting information about glacial rebound in it, something I had never heard of before. Apparently there's so much ice in Antarctica and Greenland that it has pushed the bedrock below sea level. However, if it all melted, the rock would rebound back _above_ sea level.
[1]: https://www.reddit.com/r/MapPorn/comments/oehe66/antarctica_...