Blue and Green: Far beneath the flat, tranquil surface of northern Greenlands ice sheet, scientists have discovered vast ice structures as tall as skyscrapers and as wide as the island of Manhattan.
The formations are caused when ice at the base of the glacier melts and refreezes over hundreds of years, in a process that may be quickening the glaciers slide into the sea.
Using radar from airborne surveys, researchers found that the structures, which cover about a tenth of northern Greenland, are made not...