Researchers analysed fossils found on a cliff face in New Zealand
New research suggests Antarctica 40 million years ago had a warmer climate than previously thought with little or no ice.
Cardiff University researchers analysed fossils from sediments on a cliff in South Island, New Zealand.
New Zealand was around 1,100km further south 40 million years ago, so was much closer to Antarctica.
The surface sea temperature would have been around 23-25C (73-77F), higher than off the South African coast today.
The research has been published in the journal Geology this week by a team of scientists from the university.
Antarctica is the coldest place on Earth
98% is covered by ice
Antarctica is divided in two by the Transantarctic Mountains
The highest peak is 4,892 metres
Antarctica is home to more than 70 lakes that lie below the continental ice sheet
Emilio Marcos Palma was the first person born on the Antarctic mainland, at Base Esperanza in 1978
"This is too warm to be the Antarctic water we know today," said Cat Burgess, who led the study.
"And the sea water chemistry shows there was little or no ice on the planet."
The research came from analysis of fossils of marine micro-organisms found in rocks.
"Because the fossils are so well preserved, they provide more accurate temperature records," said Miss Burgess.
"Our findings demonstrate that the water temperature these creatures lived in was much warmer than previous records have shown."
She added that several studies had suggested that greenhouse gases 40 million years ago were similar to those forecast for the end of this century and beyond.
This could provide clues about how temperatures may change in the future.
"Our work provides another piece of evidence that, in a time period with relatively high carbon dioxide levels, temperatures were higher and ice sheets were much smaller and likely to have been completely absent," she said.