Warm waters run very deep.
A huge iceberg is set to break free from Antarctica. While the iceberg isn't hugely concerning, it could herald the breakup of the entire Larsen C ice shelf, which could trigger more sea-level rise.
Polar ice isn't all the same - it can be divided roughly into "land ice" and "sea ice". What matters most for sea levels is how much ice slides off the land and melts in the sea.
Researchers find that ice around Antarctica shrank quickly last decade, raising concerns over this buttress against melting land-based ice and future sea-level rise.