Recent climate, glacier changes in Antarctica at the 'upper bound' of normal

Apr 14, 2013
This photo from December 2010 shows a one-meter long section of the West Antarctic Ice Sheet Divide core, with a dark layer of volcanic ash visible. Credit: Heidi Roop

In the last few decades, glaciers at the edge of the icy continent of Antarctica have been thinning, and research has shown the rate of thinning has accelerated and contributed significantly to sea level rise.

New ice core research suggests that, while the changes are dramatic, they cannot be attributed with confidence to human-caused global warming, said Eric Steig, a University of Washington professor of Earth and space sciences.

Previous work by Steig has shown that rapid thinning of was accompanied by rapid warming and changes in near the coast. His research with Qinghua Ding, a UW research associate, showed that the majority of Antarctic warming came during the 1990s in response to El Niño conditions in the tropical Pacific Ocean.

Their new research suggests the '90s were not greatly different from some other decades – such as the 1830s and 1940s – that also showed marked temperature spikes.

"If we could look back at this region of Antarctica in the 1940s and 1830s, we would find that the would look a lot like it does today, and I think we also would find the glaciers retreating much as they are today," said Steig, lead author of a paper on the findings published online April 14 in Nature Geoscience.

The researchers' results are based on their analysis of a new ice core from the West Divide that goes back 2,000 years, along with a number of other ice core records going back about 200 years. They found that during that time there were several decades that exhibited similar as the 1990s.

The most prominent of these in the last 200 years – the 1940s and the 1830s – were also periods of unusual El Niño activity like the 1990s. The implication, Steig said, is that rapid ice loss from Antarctica observed in the last few decades, particularly the '90s, "may not be all that unusual."

The same is not true for the , the part of the continent closer to South America, where rapid ice loss has been even more dramatic and where the changes are almost certainly a result of human-caused warming, Steig said.

But in the area where the new research was focused, the West Sheet, it is more difficult to detect the evidence of human-caused climate change. While changes in recent decades have been unusual and at the "upper bound of normal," Steig said, they cannot be considered exceptional.

"The magnitude of unforced natural variability is very big in this area," Steig said, "and that actually prevents us from answering the questions, 'Is what we have been observing exceptional? Is this going to continue?'"

He said what happens to the Ice Sheet in the next few decades will depend greatly on what happens in the tropics.

The is made up of layers of ice, greatly compressed, that correspond with a given year's precipitation. Similar to tree rings, evidence preserved in each layer of ice can provide climate information for a specific time in the past at the site where the ice core was taken.

In this case, the researchers detected elevated levels of the isotope oxygen 18 in comparison with the more commonly found oxygen 16. Higher levels of oxygen 18 generally indicate higher air temperatures.

Levels of oxygen 18 in samples from the 1990s were more elevated than for any other time in the last 200 years, but were very similar to levels reached during some earlier decades.

Explore further: NASA's HS3 mission spotlight: The HIRAD instrument

More information: Paper: DOI: 10.1038/ngeo1778

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antigoracle
2.1 / 5 (22) Apr 14, 2013
New ice core research suggests that, while the changes are dramatic, they cannot be attributed with confidence to human-caused global warming, said Eric Steig, a University of Washington professor of Earth and space sciences

And so the AGW Alarmist lie and agenda crumbles.
TheBoss
1.4 / 5 (11) Apr 14, 2013
Now you people have to remember we do have an impact on the environment. We don't even have an understanding of how complex earths weather systems can be. It's always changing and we're left in the dark.
NikFromNYC
2.3 / 5 (18) Apr 14, 2013
"In the last few decades, glaciers at the edge of the icy continent of Antarctica have been thinning, and research has shown the rate of thinning has accelerated and contributed significantly to sea level rise."

Lies point to scientific fraud at work. Antarctic ice is increasing steadily, not declining, not melting, growing. This is established, non-controversial, peer reviewed basic data, basic facts of the case.

Sea level is rising at *exactly* the same rate now going on 150 years of real worldwide tide gauge data:

http://s10.postim...mage.jpg

The small inset graph is the standard Church & White average of tide gauges, and shows utterly no high CO2 era (post 1945 industrial boom) trend change.
runrig
4.2 / 5 (15) Apr 14, 2013
New ice core research suggests that, while the changes are dramatic, they cannot be attributed with confidence to human-caused global warming, said Eric Steig, a University of Washington professor of Earth and space sciences

And so the AGW Alarmist lie and agenda crumbles.


Rather selective of you I feel....

"The same is not true for the Antarctic Peninsula, the part of the continent closer to South America, where rapid ice loss has been even more dramatic and where the changes are almost certainly a result of human-caused warming, Steig said.
runrig
4 / 5 (12) Apr 14, 2013
"In the last few decades, glaciers at the edge of the icy continent of Antarctica have been thinning, and research has shown the rate of thinning has accelerated and contributed significantly to sea level rise."

Lies point to scientific fraud at work. Antarctic ice is increasing steadily, not declining, not melting, growing. This is established, non-controversial, peer reviewed basic data, basic facts of the case.


Err - this is talking about ice-sheet, as in land based ice. Not sea-ice, which as we all know has the variable of salinity involved.
ScooterG
2.3 / 5 (18) Apr 14, 2013
More and more rats are jumpin' the AGW ship, cuz she's headed down.
gmarster
1 / 5 (8) Apr 15, 2013
Why do scientists interact with the public with apprehension. Because the public isn't interested in the scientific process. Give an answer right now and if latter that answer was wrong you were either incompetent or LYING! Scientific "consensus" starts looking a lot like scientists who would disagree just moving on to other issues they won't get harassed for.
antigoracle
1.6 / 5 (14) Apr 15, 2013
Why do scientists interact with the public with apprehension. Because the public isn't interested in the scientific process. Give an answer right now and if latter that answer was wrong you were either incompetent or LYING! Scientific "consensus" starts looking a lot like scientists who would disagree just moving on to other issues they won't get harassed for.

In other professions, let's say medicine, when you are wrong people die, and you pay the consequences. In research science the peer review process is meant to protect researchers from what you described. However, in recent times, the AGW Alarmist Cult has dishonored this process and science as a whole, just to get their greedy hands on the lucrative grant. Climate studies have forever been tarnished by them, and what's particularly disturbing is that these people are still at their "jobs" doing more harm. In any other scientific discipline these "scientist" would be outcasts.
Dug
1 / 5 (5) Apr 15, 2013
Somewhat contradictory articles in the same newsletter:
http://phys.org/n...tml#nwlt
Dug
2.3 / 5 (9) Apr 15, 2013
NikFromNYC - It isn't exactly a secret, just basic facts ignored by the public - that satellite elevation accuracy is /- 20mm, but they are trying to measure single or even fractional mm increments - and the constant disagreement with tidal gauge measurement results reflect this inaccuracy. It's another well known fact that orbit decay also affects satellite sea level measurement accuracy requiring frequent "corrections" of data - also an another opportunity to adjust for consensus. The satellite elevation error problem used to have it's own discussion section in Wikipedia's Current Sea Level Rise article:

(http://en.wikiped...urement)

but it's now buried within and near the bottom of the article - and though the error is discussed, it is no longer under a separate topic title of "satellite seal level error." This is our new democratized "science." One where "consensus" is more important than fact.