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  BBC 31 May 06
Arctic's tropical past uncovered
By Rebecca Morelle Science reporter, BBC News

ENN 1 Jun 06
Scientists Say Arctic Once Was Tropical
 By Seth Borenstein, Associated Press

WASHINGTON: Scientists have found what might have been the ideal ancient vacation hotspot with a 74-degree Fahrenheit average temperature, alligator ancestors and palm trees. It's smack in the middle of the Arctic.

First-of-its-kind core samples dug up from deep beneath the Arctic Ocean floor show that 55 million years ago an area near the North Pole was practically a subtropical paradise, three new studies show.

The scientists say their findings are a glimpse backward into a much warmer-than-thought polar region heated by run-amok greenhouse gases that came about naturally.

Skeptics of man-made causes of global warming have nothing to rejoice over, however.

The researchers say their studies appearing in Thursday's issue of Nature also offer a peek at just how bad conditions can get. "It probably was (a tropical paradise) but the mosquitoes were probably the size of your head," said Yale geology professor Mark Pagani, a study co-author.

And what a watery, swampy world it must have been.

"Imagine a world where there are dense sequoia trees and cypress trees like in Florida that ring the Arctic Ocean," said Pagani, a member of the multinational Arctic Coring Expedition that conducted the research.

Millions of years ago the Earth experienced an extended period of natural global warming. But around 55 million years ago there was a sudden supercharged spike of carbon dioxide that accelerated the greenhouse effect.

Scientists already knew this "thermal event" happened but are not sure what caused it. Perhaps massive releases of methane from the ocean, the continent-sized burning of trees, lots of volcanic eruptions.

Many experts figured that while the rest of the world got really hot, the polar regions were still comfortably cooler, maybe about 52 degrees Fahrenheit. But the new research found the polar average was closer to 74 degrees.

So instead of Boston-like weather year-round, the Arctic was more like Miami North. Way north.

"It's the first time we've looked at the Arctic, and man, it was a big surprise to us," said study co-author Kathryn Moran, an oceanographer at the University of Rhode Island. "It's a new look to how the Earth can respond to these peaks in carbon dioxide."

It's enough to make Santa Claus break into a sweat. The 74-degree temperature, based on core samples which act as a climatic time capsule, was probably the year-round average, but because data is so limited it might also be just the summertime average, researchers said.

What's troubling is that this hints that future projections for warming, several degrees over the next century, may be on the low end, said study lead author Appy Sluijs of the Institute of Environmental Biology at Utrecht University in the Netherlands.

Also it shows that what happened 55 million years ago was proof that too much carbon dioxide -- more than four times current levels -- can cause global warming, said another co-author Henk Brinkhuis at Utrecht University.

Purdue University atmospheric sciences professor Gabriel Bowen, who was not part of the team, praised the work and said it showed that "there are tipping points in our (climate) system that can throw us to these conditions."

And the new research also gave scientists the idea that a simple fern may have helped pull Earth from a hothouse to an icehouse by sucking up massive amounts of carbon dioxide.

Unfortunately, this natural solution to global warming was not exactly quick: It took about a million years. With all that heat and massive freshwater lakes forming in the Arctic, a fern called Azolla started growing and growing. Azolla, still found in warm regions today, grew so deep, so wide that eventually it started sucking up carbon dioxide, Brinkhuis theorized. And that helped put the cool back in the Arctic.

Bowen said he has a hard time accepting that part of the research, but Brinkhuis said the studies show tons upon tons of thick mats of Azolla covered the Arctic and moved south. "This could actually contribute to push the world to a cooling mode," Brinkhuis said, but only after it got hotter first and then it would take at least 800,000 years to cool back down. It's not something to look forward to, he said.

BBC 31 May 06
Arctic's tropical past uncovered
By Rebecca Morelle Science reporter, BBC News

Fifty-five million years ago the North Pole was an ice-free zone with tropical temperatures, according to research.

A sediment core excavated from 400m (1,300ft) below the seabed of the Arctic Ocean has enabled scientists to delve far back into the region's past. An international team has been able to pin-point the changes that occurred as the Arctic transformed from green house to ice house. The findings are revealed in a trio of papers published in the journal Nature.

Unlocked secrets

Until now, our understanding of the Arctic's environmental history has been limited because of the difficulties in retrieving material from the harsh, ice-covered region. But in 2004, the Arctic Coring Expedition (Acex) used ice-breaking ships and a floating drilling rig to remove 400m-long cylinders of sediment from the bottom of the ocean floor. The cores were taken from the 1,500km (930 mile) long Lomonosov Ridge, which stretches between Siberia and Greenland.

The core holds layer upon layer of compressed fossils and minerals, which when studied can tell the story of millions of years of the Arctic's history.

The bottom end of the cylinder helped scientists to uncover what had happened to the Arctic during a dramatic global event known as the Palaeocene/Eocene Thermal Maximum, which occurred about 55 million years ago.

"This time period is associated with a very enhanced green house effect," explained Appy Sluijs, a palaeoecologist from Utrecht University in the Netherlands, and the lead author on one of the papers. "Basically, it looks like the Earth released a gigantic fart of green house gases into the atmosphere - and globally the Earth warmed by about 5C (9F).

"This event is already widely studied over the whole planet - but the one big exception was the Arctic Ocean." The core revealed that before 55 million years ago, the surface waters of the Arctic Ocean were ice-free and as warm as 18C (64F). But the sudden increase in greenhouse gases boosted them to a balmy 24C (75F) and the waters suddenly filled with a tropical algae Apectodinium .

When current climate models were applied to this period of the Earth's history, said Dr Sluijs, they predict North Pole temperatures to be about 15C (27F) lower than the core shows.

Blanket layers

The second of the three papers, led by paleaoecologist Henk Brinkhuis, also from Utrecht University, reports that the Arctic Ocean underwent another transformation about 50 million years ago.

The water changed from salty to fresh, and the ocean became covered with a thick layer of freshwater fern, called Azolla .

"We assume from climate models from the early Eocene Period that there was lots of fresh water coming into the basin via precipitation and giant Canadian and Siberian river run-offs," said Professor Brinkhuis. "And at a certain point this gave rise to this whopping great growth of Azolla ." He believes the prolific growth of this fern, may be linked to the later drops in temperature in the area. "When you have so much of this plant in this giant sea, you have a mechanism to pump out carbon dioxide from the atmosphere. It is sort of an anti-green house effect," he said. "We argue that this sits right on the break from the really warm hot house period into the time when the ice house begins."

Future predictions

Further up the core, the first evidence of ice formation emerges.

"Five hundred thousand years above where the Azolla was found, we found the first drop stones," explained Professor Brinkhuis, who is also a co-author on the third paper which details Arctic ice-formation. "These are little stones that come from icebergs, icesheets or sea ice. So it must have been cold enough to have ice."

"Before we did this it was thought that the ice field in the Northern hemisphere only began about three million years ago, but now we have pushed that back to 45 million years ago."

Although the data tells us how the world changed from one with green house conditions to one with ice house conditions millions of years ago, it may also help scientists to predict what will result from the present changes in climate.

Appy Sluijs points out that the data reveals that some of the climate models used to detail the Arctic's history got things wrong, and as they are the same models that predict our future climate they may need adjusting.

Kate Moran, lead author of one the papers and professor of oceanography and ocean engineering at University of Rhode Island, agrees: "We anticipate that our data will be used by climate modellers to give us better information about how climate change occurs and possibly where global climate might be leading.

"Today's warming of the Arctic can, in all likelihood, be attributed to mankind's impact on the planet, but as our data suggest, natural processes operating in the past have also resulted in a significant warming and cooling of the Arctic."
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