Antarctic Ice Sheet unstable at end of last ice age, new study finds

May 28, 2014
This is one of many icebergs that sheared off the continent and ended up in the Scotia Sea. Credit: Michael Weber, University of Cologne

A new study has found that the Antarctic Ice Sheet began melting about 5,000 years earlier than previously thought coming out of the last ice age – and that shrinkage of the vast ice sheet accelerated during eight distinct episodes, causing rapid sea level rise.

The international study, funded in part by the National Science Foundation, is particularly important coming on the heels of recent studies that suggest destabilization of part of the West Antarctic Ice Sheet has begun.

Results of this latest study are being published this week in the journal Nature. It was conducted by researchers at University of Cologne, Oregon State University, the Alfred-Wegener-Institute, University of Hawaii at Manoa, University of Lapland, University of New South Wales, and University of Bonn.

The researchers examined two sediment cores from the Scotia Sea between Antarctica and South America that contained "iceberg-rafted debris" that had been scraped off Antarctica by moving ice and deposited via icebergs into the sea. As the icebergs melted, they dropped the minerals into the seafloor sediments, giving scientists a glimpse at the past behavior of the Antarctic Ice Sheet.

Periods of rapid increases in iceberg-rafted debris suggest that more icebergs were being released by the Antarctic Ice Sheet. The researchers discovered increased amounts of debris during eight separate episodes beginning as early as 20,000 years ago, and continuing until 9,000 years ago.

The melting of the Antarctic Ice Sheet wasn't thought to have started, however, until 14,000 years ago.

French Research Vessel Marion Dufresne II that recovered sediment cores. Credit: Michael Weber, University of Cologne

"Conventional thinking based on past research is that the Antarctic Ice Sheet has been relatively stable since the last , that it began to melt relatively late during the deglaciation process, and that its decline was slow and steady until it reached its present size," said lead author Michael Weber, a scientist from the University of Cologne in Germany.

"The sediment record suggests a different pattern – one that is more episodic and suggests that parts of the ice sheet repeatedly became unstable during the last deglaciation," Weber added.

The research also provides the first solid evidence that the Antarctic Ice Sheet contributed to what is known as meltwater pulse 1A, a period of very rapid that began some 14,500 years ago, according to Peter Clark, an Oregon State University paleoclimatologist and co-author on the study.

The largest of the eight episodic pulses outlined in the new Nature study coincides with meltwater pulse 1A.

This is Calypso corer onboard the Marian Dufresne II research vessel and iceberg in Scotia Sea in background. Researchers used this tool to uncover the first evidence for massive and abrupt iceberg calving in Antarctica, dating back 19,000 to 9,000 years ago. Credit: Michael Weber

"During that time, the sea level on a global basis rose about 50 feet in just 350 years – or about 20 times faster than sea level rise over the last century," noted Clark, a professor in Oregon State's College of Earth, Ocean, and Atmospheric Sciences. "We don't yet know what triggered these eight episodes or pulses, but it appears that once the melting of the began it was amplified by physical processes."

The researchers suspect that a feedback mechanism may have accelerated the melting, possibly by changing ocean circulation that brought warmer water to the Antarctic subsurface, according to co-author Axel Timmermann, a climate researcher at the University of Hawaii at Manoa.

"This positive feedback is a perfect recipe for rapid rise," Timmermann said.

Some 9,000 years ago, the episodic pulses of melting stopped, the researchers say.

"Just as we are unsure of what triggered these eight pulses," Clark said, "we don't know why they stopped. Perhaps the sheet ran out of ice that was vulnerable to the physical changes that were taking place. However, our new results suggest that the Antarctic Ice Sheet is more unstable than previously considered."

Today, the annual calving of icebergs from Antarctic represents more than half of the annual loss of mass of the Antarctic Ice Sheet – an estimated 1,300 to 2,000 gigatons (a gigaton is a billion tons). Some of these giant icebergs are longer than 18 kilometers.

Explore further: West Antarctic ice sheet formed earlier than thought

More information: Paper: Millennial-scale variability in Antarctic ice-sheet discharge during the last deglaciation, dx.doi.org/10.1038/nature13397

add to favorites email to friend print save as pdf

Related Stories

Sediment wedges not stabilizing West Antarctic Ice Sheet

Sep 03, 2013

The stability of the West Antarctic Ice Sheet is uncertain as climate changes. An ice sheet such as the West Antarctic Ice Sheet that is grounded well below sea level on a bed that slopes toward the interior of the sheet ...

West Antarctic ice sheet formed earlier than thought

Oct 09, 2013

About 34 million years ago, Earth transitioned from a warm "greenhouse" climate to a cold "icehouse" climate, marking the transition between the Eocene and Oligocene epochs. This transition has been associated with the formation ...

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.

Recommended for you

Asian monsoon much older than previously thought

9 hours ago

The Asian monsoon already existed 40 million years ago during a period of high atmospheric carbon dioxide and warmer temperatures, reports an international research team led by a University of Arizona geoscientist.

Rules of thumb for climate change turned upside down

9 hours ago

With a new analysis of land regions, ETH climate researcher are challenging the general climate change paradigm that dry regions are getting drier and wet regions are getting wetter. In some regions they ...

Tropical Storm Odile taken on by two NASA satellites

Sep 12, 2014

As Tropical Storm Odile continues to affect Mexico's west coast and stir up dangerous surf, NASA's TRMM and Aqua satellites provided forecasters information on clouds and rainfall in the coast-hugging storm. ...

User comments : 18

Adjust slider to filter visible comments by rank

Display comments: newest first

katesisco
1.5 / 5 (17) May 28, 2014
Well, there is that Fermi bubble(s) sprouting from the galactic core. Perhaps this energy was responsible for 'warming up' our dying magnetar Sol. Sol's response could have been a colossal CME that explains the strange delay in our progressive ice ages noticed by Miles Mathis. See Miles Mathis Ice Ages
thermodynamics
4 / 5 (16) May 28, 2014
Well, there is that Fermi bubble(s) sprouting from the galactic core. Perhaps this energy was responsible for 'warming up' our dying magnetar Sol. Sol's response could have been a colossal CME that explains the strange delay in our progressive ice ages noticed by Miles Mathis. See Miles Mathis Ice Ages


Are you, by any chance, the love child of Rygg2 and Cantdrive?
c_bankson
4.3 / 5 (8) May 28, 2014
I suspect that global warming is caused by all those millions of cappuccino machines chugging away all over the planet.

Nothing that a meteor or a supervolcano can't fix though...
Maggnus
3.5 / 5 (11) May 28, 2014
Well, there is that Fermi bubble(s) sprouting from the galactic core. Perhaps this energy was responsible for 'warming up' our dying magnetar Sol. Sol's response could have been a colossal CME that explains the strange delay in our progressive ice ages noticed by Miles Mathis. See Miles Mathis Ice Ages


Are you, by any chance, the love child of Rygg2 and Cantdrive?
Don't hold me to it, but I think this is yet another reincarnation of Zephir.
Maggnus
3.9 / 5 (11) May 28, 2014
full-diaper gave me a one rating for that, so maybe he knows it isn't zephir? I still think it is though - let's see where the little moron ranks this one lol!!
thermodynamics
4 / 5 (12) May 28, 2014
full-diaper gave me a one rating for that, so maybe he knows it isn't zephir? I still think it is though - let's see where the little moron ranks this one lol!!


Maggy: How do you tell who is rating the posts now. I used to be able to go into my profile and see who was ranking what. However, I don't see that option anymore. I lost that ability when I lost the PM capability.
thermodynamics
3.7 / 5 (9) May 28, 2014
full-diaper gave me a one rating for that, so maybe he knows it isn't zephir? I still think it is though - let's see where the little moron ranks this one lol!!


Maggy: How do you tell who is rating the posts now. I used to be able to go into my profile and see who was ranking what. However, I don't see that option anymore. I lost that ability when I lost the PM capability.


I got it now. Truck Captain set me straight...
Vietvet
3.9 / 5 (11) May 28, 2014
@thermodynamics

I just went to your profile page, clicked see all and a new page opened showing who has voted on your comments.
thermodynamics
3.7 / 5 (9) May 28, 2014
@thermodynamics

I just went to your profile page, clicked see all and a new page opened showing who has voted on your comments.


Thanks VietVet. I appreciate the tip. Truck Captain also set me straight. Who were you with and where in Vietnam if you don't mind? I spent my time on both coasts on a gasoline tanker and a small boat repair ship. Mostly brown water. I knew the coast from Da Nang to Cua Viet pretty well.
Maggnus
3.8 / 5 (10) May 28, 2014
full-diaper gave me a one rating for that, so maybe he knows it isn't zephir? I still think it is though - let's see where the little moron ranks this one lol!!


Maggy: How do you tell who is rating the posts now. I used to be able to go into my profile and see who was ranking what. However, I don't see that option anymore. I lost that ability when I lost the PM capability.
On your own profile, go to "All" and click it.

AAANNDDDD Too Seeked!
verkle
1.6 / 5 (13) May 28, 2014
Can we please have comments related to the article, and not jabber and babbling.

Interesting to note the rapid rise of of ocean several thousand years ago.
How do we know that it was antarctic ice melt, rather than intense rain and a global flood?

InterestedAmateur
4.7 / 5 (12) May 28, 2014
Can we please have comments related to the article, and not jabber and babbling.

Interesting to note the rapid rise of of ocean several thousand years ago.
How do we know that it was antarctic ice melt, rather than intense rain and a global flood?



Wow - you have raised hypocrisy to a whole new level, it's going to be hard for anyone to top that...
thermodynamics
4.3 / 5 (12) May 28, 2014
Can we please have comments related to the article, and not jabber and babbling.

Interesting to note the rapid rise of of ocean several thousand years ago.
How do we know that it was antarctic ice melt, rather than intense rain and a global flood?



Wow - you have raised hypocrisy to a whole new level, it's going to be hard for anyone to top that...


And you have raised humor to a very high level tonight. I would have loved to have given you a 10 for this comment but I have to remain satisfied with a mere 5. Great job.
Captain Stumpy
4.4 / 5 (13) May 28, 2014
And you have raised humor to a very high level tonight. I would have loved to have given you a 10 for this comment but I have to remain satisfied with a mere 5. Great job.
@THermo
I Second this... darn near cost me a brand new laptop spitting my coffee all over it!
I think this is yet another reincarnation of Zephir
@Maggnus
I doubt it. IMHO- I could be wrong, but the syntax seems off as well. and normally Z is pretty easy to spot with his stilted style
rather than intense rain and a global flood
@verkle
because the science and facts do not support the biblical conjecture http://www.talkor...ark.html just for back-of-the-envelope calculations that show the impossibility of the act...
Nor does the spread of known species as well as diversity/location/speed-of-spreading allow for a repopulation from a single source/landing point from the biblical accounts (see Madagascar, Australia populations etc) <=strongest proof yet that flood didn't happen
Vietvet
4.2 / 5 (5) May 30, 2014
@thermodynamics

I just went to your profile page, clicked see all and a new page opened showing who has voted on your comments.


Thanks VietVet. I appreciate the tip. Truck Captain also set me straight. Who were you with and where in Vietnam if you don't mind? I spent my time on both coasts on a gasoline tanker and a small boat repair ship. Mostly brown water. I knew the coast from Da Nang to Cua Viet pretty well.


This will be somewhat redundant for readers of another thread after rggy challenged my being a vet.

As a Marine I served from Oct 66- Dec 69. Except for a month at Vietnamese language school at China Beach in Da Nang my first 13 months were spent in northern I Corps----Dong Ha, Con Thien, Cam Lo, Khe Sahn, Laos(briefly), and a lot of ground in between.

In Jan. 68 I got the transfer I had hoped for to 3rd Combined Action Group in Phu Bai. Our AO streched from Hue to Phu Loc and I got to know that area quite well over the next 23 months.

Vietvet
5 / 5 (3) May 30, 2014
Edit

I spent my first 14 months in northern I Corps, not 13.

@Thermo
The view of the South China Sea and Da Nang harbor from Hai Ban was spectacular, how was your view from the water? And when did you serve?
ccr5Delta32
2.3 / 5 (3) May 31, 2014
Climate change is the best thing to ever to humanity ' Probability of extinction not zero
thermodynamics
5 / 5 (2) May 31, 2014
Edit

I spent my first 14 months in northern I Corps, not 13.

@Thermo
The view of the South China Sea and Da Nang harbor from Hai Ban was spectacular, how was your view from the water? And when did you serve?


I served two tours in-country from 69-71. The view from the water was amazing. I got to watch Puff work out at Cua Viet often. I had the amazing experience of having the New Jersey fire over my head from a quarter of a mile off our starboard side. I got to see the ocean in all conditions for two years. As I always said, I had it a lot better than anyone not on ships. You ground pounders had the tough part.