12.5 trillion tonnes gone: Greenland and Antarctica reveal a frightening shift

Ice vanishes

Since 1979, Greenland and Antarctica have together shed roughly 12.5 trillion tonnes of ice, according to a study drawing on 27 satellite missions. The scale is almost difficult to picture: spread across the United States, the vanished ice would form a layer roughly five feet deep.

Ocean culprit

The biggest surprise lies beneath the surface. Researchers estimate around 84% of the ice loss came not from warm air melting the surface, but from warmer ocean water attacking glaciers from below and around their edges, helping huge masses of ice accelerate towards the sea.

Flood multiplier

The lost ice has already added about 3.1 cm to global sea levels. Study co-author Andrew Shepherd said the ice-sheet contribution to rising seas has put an additional 60 million to 90 million people at risk of coastal flooding, showing how seemingly small centimetres can carry enormous consequences.

 Loss accelerates

Greenland was losing around 60 billion tonnes of ice annually in the 1980s; by the 2010s, that figure had climbed to roughly 264 billion tonnes. Antarctica also saw losses accelerate sharply, while glaciers such as Jakobshavn Glacier are retreating by as much as 50 metres a day.