One way to get water with these characteristics, said Jahren, is for that water to have traveled large distances over land. As water travels over land, she explained, the heavier oxygen is removed as it rains.
The only route allowing moisture laden air to travel thousands of kilometers over land before reaching Axel Heiberg would be across North America, possibly from the Gulf of Mexico, said Jahren. "This idea is compelling because it would supply water rich in oxygen 16 and supply warm air to this very northern region"warm enough to nurture a forest.
Different Weather Patterns
Jahren finds this model of water transport intriguing "because this weather pattern is radically different from today." Current weather systems over North America tend to travel from west to east. In the Eocene epoch, a much warmer period when the poles were free of ice, weather systems could shift from south to north, said Jahren.
But there is another possible interpretation of Jahren's findings, cautioned Scott Wing, a paleontologist at the Smithsonian Institution in Washington, D.C.
"Water from snowfall also contains low quantities of oxygen 18, thus matching the water profile from the wood," he said. He suggested the possibility that snow, formed over the then ice-free Arctic Ocean, may have supplied the island with water. This would indicate that the northern regions were actually much colder than Jahren suggests.
"Isotope levels are very difficult to interpret, and there are lots of questions remaining," Wing said.
If Axel Heiberg were actually colder, it would imply that animals such as alligators, which were known to live at these latitudes, as well as plants must have been tolerant of the cold.
Whether Axel Heiberg actually received waters originating from equatorial regions is "still up for debate," said Wing.
But there are other questions left to answer. "These forests had four months of daylight and four months of complete darkness. Finding trees that could survive under these conditions is as flabbergasting as finding humans that live underwater," said Jahren.
Uncovering ancient weather patterns provides greater understanding of how ecosystems work, opening a window into the Earth's capabilities. It also offers new ideas about the kind of conditions that plants and animals might be able to survive in.
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