Key Antarctic ice shelf is within years of failure.

The article discusses the dangers of Antarctic ice shelf melting. Topics including crackup has begun at the foot of Antarctica's vulnerable Thwaites Glacier, whose melt water is already responsible for about 4% of global sea level rise; sign of impending failure is a set of diagonal fractures that nearly span the entire shelf; and incursions of warm ocean water beneath the shelf, which expedition scientists detected with a robotic submersible.