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Posted on 06/01/2009 12:37:02 PM PDT by decimon
Ancestors of tapirs and ancient cousins of rhinos living above the Arctic Circle 53 million years ago endured six months of darkness each year in a far milder climate than today that featured lush, swampy forests, according to a new study led by the University of Colorado at Boulder.
CU-Boulder Assistant Professor Jaelyn Eberle said the study shows several varieties of prehistoric mammals as heavy as 1,000 pounds each lived on what is today Ellesmere Island near Greenland on a summer diet of flowering plants, deciduous leaves and aquatic vegetation. But in winter's twilight they apparently switched over to foods like twigs, leaf litter, evergreen needles and fungi, said Eberle, curator of fossil vertebrates at the University of Colorado Museum of Natural History and chief study author.
The study has implications for the dispersal of early mammals across polar land bridges into North America and for modern mammals that likely will begin moving north if Earth's climate continues to warm. A paper on the subject co-authored by Henry Fricke of Colorado College in Colorado Springs and John Humphrey of the Colorado School of Mines in Golden appears in the June issue of Geology.
The team used an analysis of carbon and oxygen isotopes extracted from the fossil teeth of three varieties of mammals from Ellesmere Island -- a hippo-like, semi-aquatic creature known as Coryphodon, a second, smaller ancestor of today's tapirs and a third rhino-like mammal known as brontothere. Animal teeth are among the most valuable fossils in the high Arctic because they are extremely hard and better able to survive the harsh freeze-thaw cycles that occur each year, Eberle said.
Telltale isotopic signatures of carbon from enamel layers that form sequentially during tooth eruption allowed the team to pinpoint the types of plant materials consumed by the mammals as they ate their way across the landscape through the seasons, Eberle said.
"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 to escape the winter darkness, she said.
"In order for mammals to have covered the great distances across land bridges that once connected the continents, they would have required the ability to inhabit the High Arctic year-round in proximity to these land bridges," Eberle said.
Instead, the animals likely made their way south from the Arctic in minute increments over millions of years as the climate shifted. "This study may provide the behavioral smoking gun for how modern groups of mammals like ungulates -- ancestors of today's horses and cattle -- and true primates arrived in North America," said Eberle, also an assistant professor in CU-Boulder's geological sciences department.
The surprising menagerie of Arctic creatures during the early Eocene epoch, which lasted from roughly 50 million to 55 million years ago, first became evident in 1975 when a team led by Mary Dawson of the Carnegie Museum of Natural History in Pittsburg discovered fossil alligator jaw bones. Since then, fossils of aquatic turtles, giant tortoises, snakes and even flying lemurs -- one of the earliest forms of primates -- have been found on Ellesmere Island, said Eberle.
The new Geology study also foreshadows the impacts of continuing global warming on Arctic plants and animals, Eberle said. Temperatures in the Arctic are rising twice as fast as those at mid-latitudes as greenhouse gases build up in Earth's atmosphere from rising fossil-fuel burning, and air temperatures over Greenland have risen by more than 7 degrees F since 1991, according to climate scientists.
"We are hypothesizing that lower-latitude mammals will migrate north as the temperatures warm in the coming centuries and millennia," she said. If temperatures ever warm enough in the future to rival the Eocene, there is the possibility of new intercontinental migrations by mammals."
Because the oldest known tapir fossils are from the Arctic, there is the possibility that some prehistoric mammals could have evolved in the circumpolar Arctic and then dispersed through Asia, Europe and North America, said Eberle. "We may have to re-think the world of the early Eocene, when all of the Arctic land masses were connected in a supercontinent of sorts," she said.
If it was that warm then the seas really would be much higher. A bit warmer than it is now would be fine with me.
Sorry if I misread the article. I thought it said the animals fed on the plants/leaves? I can see the plants going dormant for 6 months, but if they did, did the animals hibernate? Or just starve? LOL
I think you got it, hibernate or starve. If you can’t fish or kill seals, you are really out of luck.
The interesting thing to me is how warm it used to be around the Arctic Ocean. About 220,000 years ago, brown bears made there way up there, and liked the seal fishing so much they stayed, turned white, took up Olympic swimming and became polar bears. Yep, true story, polar bears are brown bears dyed white, so the seals can’t see them, with a longer nose for sniffing the seals out when they pop up in their blow holes..
Just because it is now, does not mean that is how it always was, nor will always be.
I think i read something once that said the poles used to be reversed. That would make more sense than saying that there used to be tropical plants in an arctic area.:)
The magnetic poles, and earth's resultant magnetosphere, while they play a big part in shielding earth from the solar wind and help deflect cosmic rays, they don't have anything to do with climate. Well, unless the magnetic field drops off even more, then it could be big trouble for earth.
IMHO, climate is sun, rotation/orbit and cosmic ray dependent. It also is effected by what our solar system travels through in our journey in, around and with the Milky Way galaxy. Those influences are so big they overwhelm anything else.
Rays and particles play big parts in energy transfer when it comes to space.
One thing for sure, like with climate, we simply don't know what the magnetic poles are up to.
Ocean front property in Arizona!
Although I think the sea level rise has as much hype as globull warming.
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Thanks decimon. Another one I'd planned to post, thanks for doing the work! |
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If you mean the current scare stories then I agree.
there are plenty of plants in the arctic right now that survive a long darkness.
True? 7 degree rise since 1991? first i heard of that.
anyone know if its true?
I think climate scientist degrees are like dog years.
I understand that, but they’re adapted- and not tropical plants. Three rainy days with little sun and they start yellowing and dropping leaves, even in a greenhouse.
If the poles reverse, wouldn’t that make the north and south poles move, as well as the equator? I’m confused.
Yep, but the surf sure would be grand.
Darned Global Warming caused Global Cooling resulting in an Ice Age that killed all these holy critters and injured Mother Earth’s feelings.
Evil SUV’s held at fault for climate change.
The north magnetic pole would go where the south magnetic pole is and vice versa. The equator shouldn't be much if at all affected.
Remember that the magnetic poles are not the same as the physical poles.
One at a time, rotational spin axis first:
Spin axis is fixed, caused by earth's spin and rotation around the sun. The spin axis, as the name implies is an imaginary line through the earth at the center of rotation.
The rotational spin axis, ie north and south due to orientation of the physical earth in relation to the sun is ‘relatively’ constant and does not change much. It wobbles a little, tilts a little, these are called Milankovitch cycles, and are generally driven by sun-earth-moon orbital dynamics, taking into account the center of mass of our solar system and other variables.
Now the magnetic poles:
The magnetic poles, compass readings, are separate from the spin axis. So when they swap, the only real change is going to be your compass turns upside down, and the solar wind is going to change it's impingement direction on the earth's now reversed magnetosphere. It's only the magnetic polarity that is involved — Physically, the earth still spins the same and in relation to the sun's rotation, the north is still north, the Arctic is still in the same physical place.
The rotational dynamics of the spinning earth keeps the magnetic poles generally on the parts of the earth near where the spin axis meets the earth's surface. It is generally thought that earth's rotating liquid iron core generates it's magnetic field.
Only your compass, and particles coming from the sun, see any changes when the magnetic poles swap polarity. The weird thing is compass north does not have to point to the Arctic.
When the big magnetic switchover comes:
So what really happens when the poles swap magnetic polarity — No one knows since no human has ever observed such and event and been able to tell. One possible tough spot is if the magnetic field goes to zero and stays for any length of time, like maybe years, the solar wind is going to play havoc with earth's atmosphere, since the earth's protective magnetosphere will have collapsed. This could be really bad — We can envision how bad that might be for life on earth, but have no real way of knowing for sure.
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