It may be freezing cold and covered in ice now, but 70 million years ago the Arctic Ocean was as tepid as the Mediterranean.
In a past greenhouse world, the frigid north would have been balmy, judging from evidence in a core drilled in an ice island drifting over a ridge on the ocean floor.
Hugh Jenkyns, of the University of Oxford in England, and scientists from the Royal Netherlands Institute for Sea Research analyzed organic material in mud in the core and calculated that the mean sea surface temperature of the Arctic Ocean was 59 degrees Fahrenheit (15 degrees Celsius) about 70 million years ago.
“Further back in time if would have been even warmer, so it would have been a good place to swim,” said Jenkyns, who reported the findings in Thursday's issue of the journal Nature.
Twenty million years earlier, it could have reached 68 degrees F (20 degrees C).
“It was certainly very much a greenhouse world,” he told Reuters.
Although the scientists don’t know why it was so warm, they suspect it may have been due to high concentrations of atmospheric carbon dioxide, the greenhouse gas blamed for contributing to current global warming.
In a commentary in the journal, Christopher Poulsen of the University of Michigan, said the levels of carbon dioxide were probably three to six times what they are today, which contributed to a “super-greenhouse climate.”
“For a region blanketed in darkness for half of the year, the Arctic Ocean was astoundingly warm,” said Poulsen.