Antarctica, the world's coldest place, had a balmy, subtropical climate 53 million years ago, a team of international scientists said Friday on returning from a 57-day sojourn in the Southern Ocean, DPA reported.
The team, whose research ship docked in Hobart, Tasmania, drilled 1,000 metres into the ocean floor to extract 3,000 cores that are testimony to the changing climate.
They drilled into the ocean floor rather than on Antarctica itself because they could go deeper - and so further back in time.
Dutchman Henk Brinkhuis, co-leader of the expedition along with Spain's Carlota Escutia, said they expected to reach back 37 million years but actually managed to delve into rocks, fossils and microbes more than 50 million years old.
"We had some spectacular finds," Brinkhuis told Hobart's Mercury newspaper. "What we're doing is basically reading a history book that's been written in some really weird language."
He said studying the cores could help explain why the ice arrived - and how climate change could alter the ice sheet that covers 95 per cent of Antarctica.
"It's like a movie that you play backwards," Brinkhuis said. "Why did the earth cool down? And it cooled down and cooled down and cooled down. And at some point, it was just cold enough to begin to grow your first ice sheets."
The 143-metre JOIDES Resolution, which had 50 scientists and 65 crew on board, is a US-registered drilling vessel owned by the Joint Oceanographic Institutions for Deep Earth Sampling.