Greenland’s melt mystery unfolds

Suddenly and without warning, the gigantic river of ice sped up, causing it to spit icebergs ever faster into the ocean off southeastern Greenland.

The Helheim Glacier nearly doubled its speed in just a few years, flowing through a rift in the barren coastal mountains at a stunning 100 feet (30 meters) per day.

Alarm bells rang as the pattern was repeated by glaciers across Greenland: Was the island’s vast ice sheet, a frozen water reservoir that could raise the sea level 20 feet (6 meters) if disgorged, in danger of collapse?

Half a decade later, there’s a little bit of good news