The Great Barrier Reef suffered five "death events" over the past 30,000 years as sea levels rose and fell, forcing corals to migrate land or seaward to survive, according to decade-long work by a team of international scientists.

Researchers extracted samples from as deep as 50 metres below the seabed at sites near Mackay and Cairns off the Queensland coast to reveal how the reef has fared during abrupt changes in climate since before the last ice age.

Drilling deep into the history of the Great Barrier Reef. Credit:European Consortium for Ocean Research Drilling/International Ocean Drilling Program.

The drilling sites identified similar patterns and timing of this "natural experiment" despite being about 600 kilometres apart, said Jody Webster, an associate professor at Sydney University's School of Geosciences and lead author of a paper published in Nature Geoscience on Tuesday.

The corals shifted laterally with each sea-level change, becoming "not a barrier but a fringing reef attached to the edge of the continental shelf" during the "Last Glacial Maximum" about 20,000 years ago, he said.