THE frigid waters of the Arctic Ocean were once warm enough to swim in, according to an analysis of mud drilled from the ocean floor.
Fossil leaves from tropical plants and the remains of a cold-blooded crocodile-like reptile have previously been found in the Arctic, hinting at a warmer past. But because of the ice that blankets the ocean, few cores have been drilled from the seabed and none had yielded any data on past temperatures.
When Hugh Jenkyns of the University of Oxford examined a mud core that had been drilled in 1970, but lay wrapped in plastic in…
