An iceberg twice as big as Samoa is poised to break off Antarctica.
A rift has emerged in the Larsen C ice shelf near the continent's northernmost point.
Scientists say the 5000km square piece is hanging on by a 20km thread of ice.
The rift began nearly a decade ago, but has sped up in recent weeks. In only two weeks in December, the 100m-wide rift grew 18km.
The Larsen C ice shelf is about 350m thick, and floats on the ocean. If it breaks off, scientists fear the entire ice shelf could collapse.
"If it doesn't go in the next few months, I'll be amazed," Prof Adrian Luckman of Swansea University told BBC News.
When it happens, it'll be one of the biggest icebergs ever recorded. The biggest, known as B-15, had a surface area of 11,000 square kilometres - about the same size as Jamaica or Qatar.
In comparison, the iceberg that sunk the Titanic covered about 0.01 square kilometres.
Its loss will make it easier for glaciers to slip into the ocean, contributing to rising sea levels.
2016 was the warmest ever recorded.