Arctic thawed in prehistoric global warming

A A A

The last time massive amounts of greenhouse gases were released into the atmosphere, the North Pole was an ice-free expanse of open ocean that was teeming with tropical organisms, a study has found.

Scientists have discovered that the complete disappearance of the Arctic sea ice, 55 million years ago, coincided with a dramatic increase in concentrations of carbon dioxide or methane in the atmosphere - which must have caused global warming.

After analysiing the sediments on the floor of the Arctic Ocean, an international team of researchers working for the Arctic Core Expedition (Acex) came to the conclusion that the region was once extremely warm, unusually wet, and ice-free.

The scientists also found that the Arctic is currently experiencing one of the fastest temperature rises on record, with more sea ice melting each summer than at any time in hundreds and possibly thousands of years.

The Acex research team drilled frozen sedimentary cores from the ocean floor, which can be dated to 55 million years ago, a period known as the palaeocene-eocene thermal maximum (PETM). Surface temperatures in some parts of the world were then 8C (15F) higher than now.

"Building a picture of ancient climatic events is a lot like putting together a jigsaw puzzle, and what Acex allowed us to do was fill in a black section of the PETM picture," said Gerald Dickens, a geochemist at Rice University in Houston, Texas.

"It's difficult to overestimate the importance of this kind of experimental evidence. The Acex cores clearly show that the Arctic got very warm and wet during the PETM. Even tropical marine plants thrived in the balmy conditions [of the Arctic]," he said. The ice cores were drilled from the Lomonosov Ridge, an under-sea mountain range that stretches from northern Greenland, across the Polar Sea, to Siberia in northern Russia.

The task involved three icebreaker ships: a drilling vessel and two further ice-breakers, which protected the drilling operation from being crushed by drifting ice floes and metre-thick pack ice. This was the first time that scientists have had access to sedimentary cores drilled deep from under the Arctic.

Dr Dickens said the fossils of some microscopic plants, which can trigger algal blooms, suddenly become commonplace in the parts of the cores that are about 55 million years old. These organisms lived only in the tropics prior to the PETM warm period, suggesting the Arctic was also warm and ice-free during this period.

Scientists are not sure what caused the warming, which occurred over a relatively rapid geological period of 100,000 years. But they think it may have been due either to the release of vast deposits of carbon-containing methane stored on the sea floor, or the massive release of carbon dioxide from volcanic eruptions.

"The magnitude of the carbon input at the PETM outset is truly enormous. If it were all volcanic, you'd need something like a Vesuvius-sized eruption each day for centuries, which seems very unlikely," Dr Dickens said.

Another possibility is that there was a sudden release of massive amounts of methane and carbon dioxide that had been locked away in the deep ocean in a frozen form known as ocean gas hydrates. Even today, it is estimated that there is more carbon locked away as ocean gas hydrates than all of the oil and gas reserves of the world combined.

The latest study suggests this huge reservoir of carbon has been released in the past with devastating effects on the climate.

Arts and Entertainment
Attenborough with the primates
tvWhy BBC producers didn't want to broadcast Sir David Attenborough's famed Rwandan encounter
News
Campbell: ‘Sometimes you have to be economical with the truth’
newsFormer spin doctor says MPs should study tactics of leading sports figures like José Mourinho
Sport
football
Life and Style
Agretti is often compared to its relative, samphire, though is closer in taste to spinach
food + drink
Have you tried new the Independent Digital Edition apps?
News
Kelly Osbourne will play a flight attendant in Sharknado 2
people
News
Down-to-earth: Winstone isn't one for considering his 'legacy'
people
News
The dress can be seen in different colours
i100
Sport
Wes Brown is sent-off
football
Voices
Lance Corporal Joshua Leakey VC
voicesBeware of imitations, but the words of the soldier awarded the Victoria Cross were the real thing, says DJ Taylor
Life and Style
Alexander McQueen's AW 2009/10 collection during Paris Fashion Week
fashionMeet the collaborators who helped create the late designer’s notorious spectacles
Latest stories from i100
Have you tried new the Independent Digital Edition apps?
iJobs Job Widget
iJobs General

Recruitment Genius: Bookkeeper / Office Co-ordinator

£9 per hour: Recruitment Genius: This role is based within a small family run ...

Recruitment Genius: Designer - Print & Digital

£28000 - £32000 per annum: Recruitment Genius: This Design and marketing agenc...

Recruitment Genius: Quantity Surveyor

£46000 per annum: Recruitment Genius: This property investment firm are lookin...

Recruitment Genius: Telesales / Telemarketing Executive - OTE £30k / £35k plus

£18000 - £35000 per annum: Recruitment Genius: This company specialises provid...

Day In a Page

War with Isis: Fears that the looming battle for Mosul will unleash 'a million refugees'

The battle for Mosul will unleash 'a million refugees'

Aid agencies prepare for vast exodus following planned Iraqi offensive against the Isis-held city, reports Patrick Cockburn
Yvette Cooper: We can't lose the election. There's too much on the line

Yvette Cooper: We can't lose the election. There's too much on the line

The shadow Home Secretary on fighting radical Islam, protecting children, and why anyone in Labour who's thinking beyond May must 'sort themselves out'
A bad week for the Greens: Leader Natalie Bennett's 'car crash' radio interview is followed by Brighton council's failure to set a budget due to infighting

It's not easy being Green

After a bad week in which its leader had a public meltdown and its only city council couldn't agree on a budget vote, what next for the alternative party? It's over to Caroline Lucas to find out
Gorillas nearly missed: BBC producers didn't want to broadcast Sir David Attenborough's famed Rwandan encounter

Gorillas nearly missed

BBC producers didn't want to broadcast Sir David Attenborough's famed Rwandan encounter
Downton Abbey effect sees impoverished Italian nobles inspired to open their doors to paying guests for up to €650 a night

The Downton Abbey effect

Impoverished Italian nobles are opening their doors to paying guests, inspired by the TV drama
China's wild panda numbers have increased by 17% since 2003, new census reveals

China's wild panda numbers on the up

New census reveals 17% since 2003
Barbara Woodward: Britain's first female ambassador to China intends to forge strong links with the growing economic superpower

Our woman in Beijing builds a new relationship

Britain's first female ambassador to China intends to forge strong links with growing economic power
Courage is rare. True humility is even rarer. But the only British soldier to be awarded the Victoria Cross in Afghanistan has both

Courage is rare. True humility is even rarer

Beware of imitations, but the words of the soldier awarded the Victoria Cross were the real thing, says DJ Taylor
Alexander McQueen: The catwalk was a stage for the designer's astonishing and troubling vision

Alexander McQueen's astonishing vision

Ahead of a major retrospective, Alexander Fury talks to the collaborators who helped create the late designer's notorious spectacle
New BBC series savours half a century of food in Britain, from Vesta curries to nouvelle cuisine

Dinner through the decades

A new BBC series challenged Brandon Robshaw and his family to eat their way from the 1950s to the 1990s
Philippa Perry interview: The psychotherapist on McDonald's, fancy specs and meeting Grayson Perry on an evening course

Philippa Perry interview

The psychotherapist on McDonald's, fancy specs and meeting Grayson Perry on an evening course
Bill Granger recipes: Our chef recreates the exoticism of the Indonesian stir-fry

Bill Granger's Indonesian stir-fry recipes

Our chef was inspired by the south-east Asian cuisine he encountered as a teenager
Chelsea vs Tottenham: Harry Kane was at Wembley to see Spurs beat the Blues and win the Capital One Cup - now he's their great hope

Harry Kane interview

The striker was at Wembley to see Spurs beat the Blues and win the Capital One Cup - now he's their great hope
The Last Word: For the good of the game: why on earth don’t we leave Fifa?

Michael Calvin's Last Word

For the good of the game: why on earth don’t we leave Fifa?
HIV pill: Scientists hail discovery of 'game-changer' that cuts the risk of infection among gay men by 86%

Scientists hail daily pill that protects against HIV infection

Breakthrough in battle against global scourge – but will the NHS pay for it?