Ancient ice melt unearthed in Antarctic mud

Jul 21, 2013

Global warming five million years ago may have caused parts of Antarctica's large ice sheets to melt and sea levels to rise by approximately 20 metres, scientists report today in the journal Nature Geoscience.

The researchers, from Imperial College London, and their academic partners studied mud samples to learn about ancient melting of the East Antarctic ice sheet. They discovered that melting took place repeatedly between five and three million years ago, during a geological period called Pliocene Epoch, which may have caused sea levels to rise approximately ten metres.

Scientists have previously known that the ice sheets of West Antarctica and Greenland partially melted around the same time. The team say that this may have caused sea levels to rise by a total of 20 metres.

The academics say understanding this glacial melting during the Pliocene Epoch may give us insights into how sea levels could rise as a consequence of current global warming. This is because the Pliocene Epoch had carbon dioxide concentrations similar to now and global temperatures comparable to those predicted for the end of this century.

Dr Tina Van De Flierdt, co-author from the Department of Earth Science and Engineering at Imperial College London, says: "The Pliocene Epoch had temperatures that were two or three degrees higher than today and similar levels to today. Our study underlines that these conditions have led to a large loss of ice and significant rises in in the past. Scientists predict that global temperatures of a similar level may be reached by the end of this century, so it is very important for us to understand what the possible consequences might be."

The East Antarctic ice sheet is the largest ice mass on Earth, roughly the size of Australia. The ice sheet has fluctuated in size since its formation 34 million years ago, but scientists have previously assumed that it had stabilised around 14 million years ago.

The team in today's study were able to determine that the ice sheet had partially melted during this "stable" period by analysing the chemical content of mud in sediments. These were drilled from depths of more than three kilometres below sea level off the coast of Antarctica.

Analysing the mud revealed a chemical fingerprint that enabled the team to trace where it came from on the continent. They discovered that the mud originated from rocks that are currently hidden under the ice sheet. The only way that significant amounts of this mud could have been deposited as sediment in the sea would be if the ice sheet had retreated inland and eroded these rocks, say the team.

The academics suggest that the melting of the ice sheet may have been caused in part by the fact that some of it rests in basins below sea level. This puts the ice in direct contact with seawater and when the ocean warms, as it did during the Pliocene, the ice sheet becomes vulnerable to melting.

Carys Cook, co-author and research postgraduate from the Grantham Institute for Climate Change at Imperial, adds: "Scientists previously considered the East Antarctic ice sheet to be more stable than the much smaller ice sheets in West Antarctica and Greenland, even though very few studies of East Antarctic ice sheet have been carried out. Our work now shows that the East Antarctic ice sheet has been much more sensitive to climate change in the past than previously realised. This finding is important for our understanding of what may happen to the Earth if we do not tackle the effects of climate change."

The next step will see the team analysing sediment samples to determine how quickly the East Antarctic ice sheet melted during the Pliocene. This information could be useful in the future for predicting how quickly the could melt as a result of .

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More information: Nature Geoscience DOI 10.1038/ngeo1889

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User comments : 21

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Shootist
1.6 / 5 (31) Jul 21, 2013
Funny, how the world survived Global Warming and all.
geokstr
1.3 / 5 (27) Jul 21, 2013
And there couldn't possibly have been anything else at work in the tens of thousands of interrelated and interconnected potential drivers that may have precipitated such a melt but the ones in the current computer models either.
runrig
4.4 / 5 (14) Jul 21, 2013
And there couldn't possibly have been anything else at work in the tens of thousands of interrelated and interconnected potential drivers that may have precipitated such a melt but the ones in the current computer models either.


Correct - there couldn't - namely orbital eccentrics, as described by Milankovitch cycles.
verkle
1.1 / 5 (28) Jul 21, 2013
Interesting how science continues to find things that correlate with a past world wide flood.

Perdido
1.4 / 5 (29) Jul 21, 2013
Well. How does the fact that the Antarctic has been increasing in ice volume these last few decades impact the newest predictions on CO2 and AGW?
Hint: Increases in CO2 volumes occur AFTER the warming, it is not the cause of it.
sennekuyl
4.4 / 5 (13) Jul 21, 2013
Verkle, the problem isn't world wide catastrophes, however the timing is a little off. Assuming you are implying a correlation with one of the many 'Noah's' ark stories, 5 million years ago, humans weren't exactly up to building massive wooden boats, let alone capable of containing all animal species (http://arstechnic...tinct/).

And there is the problem of water: it would need to be 9km all over the globe, not the sea level 20m higher. And then there is the problem of the catastrophes being too slow. It has been calculated @ 150 days before dry land was allegedly observed. I can't see a time frame for the length of time it would have been around, but I can't see it happening in less than a decade, though it probably lasted centuries.

EDIT: Article seems to indicate it was over 2 million years.
thermodynamics
4.5 / 5 (16) Jul 21, 2013
Verkle said:
Interesting how science continues to find things that correlate with a past world wide flood.


Sorry Verkle, as senne said, 20 meters will not cover the earth, only the low spots. There is no support for the fable of a worldwide flood. This article did not "find things that correlate with a past world wide flood."

Give up on trying to shoehorn your fables onto a sciences site.
thermodynamics
5 / 5 (16) Jul 21, 2013
Period: You said
Well. How does the fact that the Antarctic has been increasing in ice volume these last few decades impact the newest predictions on CO2 and AGW?
Hint: Increases in CO2 volumes occur AFTER the warming, it is not the cause of it.


Since you don't understand the interaction of the orbit of the earth, the role of the atmosphere, plants, human interactions with the world and CO2, I will spell this out again. Please take notes this time. Read the article below on Milankovitch cycles as a start.

http://en.wikiped...h_cycles

The article shows how cycles start and stop.

Once heating starts due to orbital change it starts driving CO2 out of the oceans and land and into the atmosphere. The additional CO2 driven into the atmosphere provides feedback for more heating. Or, that was the way it worked before humans started pumping CO2 into the atmosphere. (continued)
thermodynamics
4.8 / 5 (17) Jul 21, 2013
Continued: in the past CO2 responded to the heating by releasing mire CO2 and water vapor and then started providing increased heating due to feedback. Now we are at the start of an unprecedented event where humans are changing the concentration of CO2 in the atmosphere.

The beginning of oxygen producing organisms was the only compable change in the atmosphere by biological organisms.

The change in CO2 has started heating the Earth this time. Now, even though there is no heating favoring Milankovich cycles, the CO2 is leading the heating.

Do you understand that it is exactly this fact, that CO2 used to follow, and is now leading that is one of the strongest signals of the anthropogenic contribution to global warming?

If I need to use smaller words, let me know. Many of us have explained this simple concept on this site before.
meBigGuy
4.8 / 5 (16) Jul 22, 2013
It is so sad to see people raise the issue of CO2 lagging warming and their inability to see that the lagging increase in CO2 in the past is a powerful indicator of positive feedback. Seems we are discovering more and more positive feedback mechanisms, not the negative ones I would hope for.

Also, hearing idiots say "the world will survive" ..... They are simply off topic. The survival issues are about the economies and civilization as they currently exist, not the Earth.
NikFromNYC
1.2 / 5 (21) Jul 22, 2013
Well. How does the fact that the Antarctic has been increasing in ice volume these last few decades....


Indeed the ICESat satellite found that exactly half of overall ice mass loss in Greenland, which is along the edges despite a growing central mass, was compensated by mass gains in Antarctica. Bad solder joints on the altimetry lasers only allowed five years of data though but it is strong support of a simple model of ice in which all those scare headlines about ice breaking off are due to everyday ice mass growth in a mildly warming and thus more humid world.
katesisco
1 / 5 (20) Jul 23, 2013
I too have read that the increase in co2 comes after the warming. I have been considering how this would happen when I read WORLD WITHOUT ICE national geo 2011 regarding the heating event 9 million years after the 65 my extinction event of the dinos. It is not known what caused it but the carbon increase is suspected to be from the melting of the methane hydrates. The article states it took 150,000 years to sequester this carbon saturation. Several species of foraminerafera living on the sea floor went extinct. Mammals shrunk in body size. Leaves were perhaps less nutritious so maybe that means there were less mineral content--all over. Maybe stress due to radiation.
antigoracle
1.2 / 5 (23) Jul 23, 2013
And there couldn't possibly have been anything else at work in the tens of thousands of interrelated and interconnected potential drivers that may have precipitated such a melt but the ones in the current computer models either.


Correct - there couldn't - namely orbital eccentrics, as described by Milankovitch cycles.

Nah, according to AGW Alarmist Cult scripture it has to be CO2, so my guess is whales breathing and farting too much.
deepsand
3.1 / 5 (19) Jul 24, 2013
Well. How does the fact that the Antarctic has been increasing in ice volume these last few decades impact the newest predictions on CO2 and AGW?
Hint: Increases in CO2 volumes occur AFTER the warming, it is not the cause of it.

Not only d increases in CO2 not always follow warming, but also precede it, but those that do follow warming only serve to increase such warming.

Next time get all of the facts before speaking.
deepsand
2.9 / 5 (19) Jul 24, 2013
And there couldn't possibly have been anything else at work in the tens of thousands of interrelated and interconnected potential drivers that may have precipitated such a melt but the ones in the current computer models either.


Correct - there couldn't - namely orbital eccentrics, as described by Milankovitch cycles.

Nah, according to AGW Alarmist Cult scripture it has to be CO2, so my guess is whales breathing and farting too much.

Given your fascination with anal orifices we'll take your word re. whale farts.
deepsand
3.1 / 5 (19) Jul 24, 2013
Well. How does the fact that the Antarctic has been increasing in ice volume these last few decades....

Indeed the ICESat satellite found that exactly half of overall ice mass loss in Greenland, which is along the edges despite a growing central mass, was compensated by mass gains in Antarctica.

What the hell has Greenland to do with Antarctica?
antigoracle
1.2 / 5 (20) Jul 24, 2013
And there couldn't possibly have been anything else at work in the tens of thousands of interrelated and interconnected potential drivers that may have precipitated such a melt but the ones in the current computer models either.


Correct - there couldn't - namely orbital eccentrics, as described by Milankovitch cycles.

Nah, according to AGW Alarmist Cult scripture it has to be CO2, so my guess is whales breathing and farting too much.

Given your fascination with anal orifices we'll take your word re. whale farts.

Well, every bit of ignorant filth you speak, comes out of an anal orifice and your abject stupidity does facinate me.
deepsand
3 / 5 (18) Jul 28, 2013
Wherein Mr. Anal Orifice himself describes what he sees when he looks into a mirror.
VendicarE
4.6 / 5 (10) Jul 28, 2013
"How does the fact that the Antarctic has been increasing in ice volume " - DildoBilbo

When you start a question off with a lie, expect to be treated like a moron, BilboDildo
VendicarE
4.3 / 5 (11) Jul 28, 2013
"What the hell has Greenland to do with Antarctica?" - DeepSand

North, South, here, there, Up, Down, it is all the same to the mentally diseased, Denialist brain.

Death is the only cure.
full_disclosure
1 / 5 (12) Jul 31, 2013
"What the hell has Greenland to do with Antarctica?" - DeepSand

North, South, here, there, Up, Down, it is all the same to the mentally diseased, Denialist brain.

Death is the only cure.


Idiot