The West Antarctic ice sheet is collapsing, and there's nothing we can do about it. The collapse has been reported by two different teams of scientists - in the journals of Science and Geophysical Research Letters.

The Thwaites Glacier on the West Antarctic Ice Sheet. Credit: NASA

The New York Times explains:
The basic problem is that much of the West Antarctic ice sheet sits below sea level in a kind of bowl-shaped depression [in] the earth. As Dr. Mercer outlined in 1978, once the part of the ice sheet sitting on the rim of the bowl melts and the ice retreats into deeper water, it becomes unstable and highly vulnerable to further melting
It means an inevitable 10-foot rise in sea level. We are now in the Danger Zone. [Science and NASA via New York Times]