The North Pole sinks in the dark winter 53 million years ago

The ancestors of tapirs and ancient relatives of rhinos above the Arctic Ring 53 million years ago lived in the darkness for 6 months each year with more mild weather conditions than today, according to a study. of the University of Colorado at Boulder.

CU-Boulder Professor Jaelyn Eberle said the study shows that some prehistoric mammals weigh about 1,000 pounds, living in an area that is now Ellesmere Island near Greenland. Their summer rations are plants with flowers, leaves and plants underwater, but in the winter they switch to food like twigs, green needles and mushrooms, according to Eberle, the fossilist in charge. Vertebrates at the Museum of Natural History, University of Colorado and also the team leader.

This study is important for understanding the distribution of ancient mammals along the strip of land connecting the polar regions with North America, as well as for the northern movement of animals that have Modern breast if the Earth's climate continues to warm up. An article on this topic, with co-author Henry Fricke of Colorado College in Colorado Springs and John Humphrey of the Colorado Mining School in Golden is published in the June issue of Geology.

The team used carbon isotope analysis and oxygen extracted from fossil teeth from three Ellesmere Island mammalian groups - a hippopotamus-like, half-aquatic animal called Coryphodon, a species. another is the ancestor of today's tapir, and the third is a rhino-like mammal called brontothere. Animal teeth are one of the most important fossils in the Arctic region, because they are difficult to survive the freezing and thawing cycles that occur each year.

Carbon isotope markers from the enamel layers that form in the teething period allow the team to determine the type of plants that these animals consume.

Eberle said: 'We use isotope signs in enamel to show that these mammals are not migrating or hibernating. Instead, they live in the high Arctic region throughout the year, eating strange foods during the winter months . ' The research is funded by the National Science Foundation.

Oxygen isotope analysis from fossil teeth helps determine seasonal changes in surface drinking water based on precipitation and temperature, providing additional climate information. The results indicate warm and humid summers and mild winters in the high Arctic region 53 million years ago , where temperatures range from a little above freezing to 70 degrees Fahrenheit, Eberle explained.

A hippopotamus mammal, called Coryphodon, is one of the ancient mammalian groups that live in the darkness in the Arctic 53 million years ago, according to a new study by the University of Colorado at Boulder. (Photo: American Museum of Natural History / D. Finnin).

The environment in the center of Ellesmere Island, located at 80 degrees north latitude, is part of a much larger Arctic circle at that time. It may be like the swamp forest of southeastern United States today, and contains fossil tree stumps as large as washing machines.

Ellesmere Island center is in the high Arctic region today - polar regions with tundra, permafrost, sparse vegetation and some mammals - temperatures ranging from minus 37 degrees Fahrenheit winter to 48 degrees F in summer, this is the coldest and driest environment on Earth. The sunshine only appears from October to February, and from mid-April to the end of August, this polar area is covered in darkness. The year-round occurrence of mammals like Coryphdon species like hippopotamus, tapirs and brontotheres in the high Arctic is a 'condition' for distribution along the high latitude strip that geologists believe connects. adjacent to Asia and Europe with North America. Dietary chemical indications, and fossil evidence deny the idea of ​​the seasonal migration of these animals to escape the winter night.

"In order to cover the distance along the strips of land that once connected the continents, these mammals must be able to live in the high Arctic year round," Eberle said .

Instead, these animals move southward for millions of years when climate changes. Eberle said: 'This study could give an explanation for how these groups of mammals such as ungulates - ancestors of horses and cattle today - and primates reach North America. '.

The surprising number of animals in the Arctic in the early Eocene period, which lasted 50 to 55 million years ago, was first unveiled in 1975 when a team under Mary's direction Dawson of the Carnegie Natural History Museum in Pittsburg discovered fossil bones of crocodiles. Since then, fossils of water turtles, giant tortoises, snakes, and even flying lemurs - one of the earliest forms of primates - have been discovered at Ellesmere Island.

The new study also signals the impact of global warming on Arctic plants and animals. The temperature in the Arctic is growing twice as fast as those in the middle latitude, because greenhouse gases are concentrated in the Earth's atmosphere from burning fossil fuels, and the air temperature in Greenland has increased. more than 7 degrees F since 1991.

Eberle said: 'We hypothesize that mammals in lower latitudes will migrate to the North, as temperatures continue to rise in the coming centuries. If the future temperature is equivalent to the Eocene century, it is very likely that there will be transcontinental migration of mammals. '

Because the oldest fossil fossil found in the Arctic, it is possible that some prehistoric mammals evolved from the Arctic arc and dispersed to Asia, Europe and North America, Eberle admitted. determined. 'We may very well have to reconsider the early Eocene world, when all the Arctic lands are connected to the continents'.