"We were able to use carbon signatures preserved in the tooth enamel to show that these mammals did not migrate or hibernate," said Eberle. "Instead, they lived in the high Arctic all year long, munching on some unusual things during the dark winter months." The study was funded by the National Science Foundation.
An analysis of oxygen isotopes from the fossil teeth helped determine seasonal changes in surface drinking water tied to precipitation and temperature, providing additional climate information, said Eberle. The results point to warm, humid summers and mild winters in the high Arctic 53 million years ago, where temperatures probably ranged from just above freezing to near 70 degrees Fahrenheit, Eberle said.
The environment on central Ellesmere Island, located at about 80 degrees north latitude, was part of a much larger circumpolar Arctic region at the time, she said. It probably was similar to swampy cypress forests in the southeast United States today and still contains fossil tree stumps as large as washing machines, Eberle said.
On central Ellesmere Island in today's high Arctic -- a polar desert that features tundra, permafrost, ice sheets, sparse vegetation and a few small mammals -- the temperature ranges from roughly minus 37 degrees F in winter to 48 degrees F in summer and is the coldest, driest environment on Earth. There is sunlight in the high Arctic between October and February, and the midnight sun is present from mid-April through the end of August.
The year-round presence of mammals such as the hippo-like Coryphodon, tapirs and brontotheres in the high Arctic was a "behavioral prerequisite" for their eventual dispersal across high-latitude land bridges that geologists believe linked Asia and Europe with North America, Eberle said. Their dietary chemical signatures, portly shapes and fossil evidence for babies and juveniles in the Arctic preclude the idea of long, seasonal migrations t
|Contact: Jaelyn Eberle|
University of Colorado at Boulder