Ice Age thaw signalled 1,000 years earlier

The Atlantic Ocean at mid-depths may have given out early warning signals - 1,000 years in advance - that the last Ice Age was going to end, says a study.

Scientists had earlier thought that at the end of the last Ice Age, around 14,700 years ago, major changes occurred to the Atlantic Ocean in a period known as the Bolling-Allerod interval.

Since glaciers melted and the earth warmed during that period, the currents of Atlantic Ocean at its deepest levels changed direction.

Researchers have analysed the chemistry of 24 ancient coral fossils from the North Atlantic Ocean to learn more about the circulation of its waters during the last Ice Age.

"The coral fossils we have studied are showing us that the North Atlantic Ocean at mid-depths was undergoing changes up to 1,000 years earlier than we had expected. The tantalising prospect is that this high variability may have been a signal that the last Ice Age was about to end," said David Wilson at Imperial College London.

The corals recorded a high variability in the currents of the Atlantic Ocean at mid-depths, around two km below the surface, up to 1,000 years prior to the Bolling-Allerod interval.

These changes gave an early warning that the world was to switch from its glacial state to the warmer world we know today, said the team.

The team studied fossil corals from a species called Desmophyllum dianthus, that typically live for 100 years. This gave the team a rare insight into what was happening to the ocean's currents during this relatively brief time.

The study appeared in the journal Paleoceanography.