Study links Greenland ice sheet collapse, sea level rise 400,000 years ago
CORVALLIS, Ore. – A new study suggests that a warming period more than 400,000 years ago pushed the Greenland ice sheet past its stability threshold, resulting in a nearly complete deglaciation of southern Greenland and raising global sea levels some 4-6 meters.
The study is one of the first to zero in on how the vast Greenland ice sheet responded to warmer temperatures during that period, which were caused by changes in the Earth’s orbit around the sun.
Results of the study, which was funded by the National Science Foundation, are being published this week in the journal Nature.
“The climate 400,000 years ago was not that much different than what we see today, or at least what is predicted for the end of the century,” said Anders Carlson, an associate professor at Oregon State University and co-author on the study. “The forcing was different, but what is important is that the region crossed the threshold allowing the southern portion of the ice sheet to all but disappear.
“This may give us a better sense of what may happen in the future as temperatures continue rising,” Carlson added.
Few reliable models and little proxy data exist to document the extent of the Greenland ice sheet loss during a period known as the Marine Isotope Stage 11. This was an exceptionally long warm period between ice ages that resulted in a global sea level rise of about 6-13 meters above present. However, scientists have been unsure of how much sea level rise could be attributed to Greenland, and how much may have resulted from the melting of Antarctic ice sheets or other causes.
To find the answer, the researchers examined sediment cores collected off the coast of Greenland from what is called the Eirik Drift. During several years of research, they sampled the chemistry of the glacial stream sediment on the island and discovered that different parts of Greenland have unique chemical features. During the presence of ice sheets, the sediments are scraped off and carried into the water where they are deposited in the Eirik Drift.
“Each terrain has a distinct fingerprint,” Carlson noted. “They also have different tectonic histories and so changes between the terrains allow us to predict how old the sediments are, as well as where they came from. The sediments are only deposited when there is significant ice to erode the terrain. The absence of terrestrial deposits in the sediment suggests the absence of ice.
“Not only can we estimate how much ice there was,” he added, “but the isotopic signature can tell us where ice was present, or from where it was missing.”
This first “ice sheet tracer” utilizes strontium, lead and neodymium isotopes to track the terrestrial chemistry.
The researchers’ analysis of the scope of the ice loss suggests that deglaciation in southern Greenland 400,000 years ago would have accounted for at least four meters – and possibly up to six meters – of global sea level rise. Other studies have shown, however, that sea levels during that period were at least six meters above present, and may have been as much as 13 meters higher.
Carlson said the ice sheet loss likely went beyond the southern edges of Greenland, though not all the way to the center, which has not been ice-free for at least one million years.
In their Nature article, the researchers contrasted the events of Marine Isotope Stage 11 with another warming period that occurred about 125,000 years ago and resulted in a sea level rise of 5-10 meters. Their analysis of the sediment record suggests that not as much of the Greenland ice sheet was lost – in fact, only enough to contribute to a sea level rise of less than 2.5 meters.
“However, other studies have shown that Antarctica may have been unstable at the time and melting there may have made up the difference,” Carlson pointed out.
The researchers say the discovery of an ice sheet tracer that can be documented through sediment core analysis is a major step to understanding the history of ice sheets in Greenland – and their impact on global climate and sea level changes. They acknowledge the need for more widespread coring data and temperature reconstructions.
“This is the first step toward more complete knowledge of the ice history,” Carlson said, “but it is an important one.”
Lead author on the Nature study is Alberto Reyes, who worked as a postdoctoral researcher for Carlson when both were at the University of Wisconsin-Madison. Carlson is now on the faculty in Oregon State’s College of Earth, Ocean, and Atmospheric Sciences.
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Earth’s orbit? Whatever. We all know it was the Neanderthals use of fire that caused the collapse
Mr. Abbott how much CO2 do we need to take out of the atmosphere to prevent a 5m sea level rise from orbital changes? Will that also make the dark, sooty snow less CO2ey?
James Abbott says:
So it might not be a good idea to keep increasing CO2 concentration in the atmosphere. How would we defend coastal cities from a 5m sea level rise ?
Non-sequitur. The two statements have no relationship. CO2 does not cause sea level rise.
More CO2 is a good thing, as demonstrated by a measurable GREENING of the earth from the current CO2 rise. There is no downside, because there is no evidence of any global harm from that beneficial trace gas. More is better.
If sea levels began to rise to 5 meters, it would mean most of the polar ice has to melt. Since there is no indication whatever that that is happening, Abbott’s statement comes across as a wild-eyed Chicken Little scare.
Relax, Abbott, it was only an acorn.
The last interglacial, the Eemian, was a couple degrees warmer than today for around 4,000 years, and yet the Greenland ice cap survived. I think we have some breathing room on this crisis.
so they sampling a sand bar and trying to claim they can tell how much ice was on Greenland 400,000 years ago … BS times 10 …
The southern third of Greenland is too far south to have glaciers. It only has glaciers today because the northern/central region has been accumulating ice for 2.5 million years. Gravity has pushed it down to cover the southern region. And then 100,000 year ice ages ensure it stays in the southern third …
… except when an interglacial period lasts more than 15,000 years. It just takes a certain amount of time to melt out all that ice at today’s temperature levels.
The interglacial at 400,000 years ago was 25,000 years long and temperatures were similar to today. Same with the interglacial 800,000 years ago. In both these interglacials, the southern third of Greenland melted out and small trees even grew there.
The current interglacial is projected to be the longest one yet. Lasting at least 52,000 years morel and, more likely, 125,000 years. Far northern summer solar insolation will decline by a tiny amount (0.5 W/m2) in the next 2,000 years, leaving it well above the limit needed to melt the snow in the summer on non-glaciated land. It will then go back up again and stay above the limit needed to melt the snow in the summer for the next 50,000 years after this. It will be touch and go at this time, but solar insolation will then increase again after this time, staying high until 125,000 years from now.
The southern third of Greenland will not have glaciers in about 2,000 or 3,000 years. The central part will melt out over the next 20,000 years.
It is just what the Milankovitch cycles project. We can be reasonably accurate about this for as much as 5 million years out after which there are too many uncertainties.
Nobody will be around to check this forecast, but it is what it is.
James Abbott asks, “How would we defend coastal cities from a 5m sea level rise ?” – if such a thing were to happen for whatever reason.
The answer to your question is “Dikes”. When I lived in Holland I was 8 metres below sea level, so it’s already existing technology.
Forget Milankovitch, the real problem is dark energy flux. Just divide by the square root of minus 1. Get a term that is equal even though it differs over a range of 2. Mathematics is the art of making two different things the same.
“…as temperatures continue rising”???
Shouldn’t that be if or when?
This was an exceptionally long warm period between ice ages that resulted in a global sea level rise of about 6-13 meters above present.
So let’s get this straight.
Longer duration of an interglacial means more sea level rise.
So it is normal to see sea level rise throughout an interglacial.
BUT [scary organ music in background]
Current sea level rise is different.
It is not natural.
Oh no.
It is because of our SINS! [Wails of religious angst and self-loathing]
It can only be CO2.
Human activity is the only possible cause of climate change.
How long will these mendacious morons get away with peddling this crap?
James Abbott says:
June 25, 2014 at 5:09 pm
Vercigenitorex – very true. But we have some control over whether the planet continues to warm over the coming centuries
Oh oh the man behind the curtain has appeared. and how do we have control over the climate then James ?? You have some magic extremely high powered control machine do you ?
Oh sorry your second name is Jesus. Which lunatic asylum did you escape from ?
How long will these mendacious morons get away with peddling this crap?
For as long as the other mendacious morons in government need the taxes to spend.
I would like to chime in with others who have noted that this is a misuse of the word “collapse.” Correct usage of the word suggests speed and suddenness, in its primary definition: “To break apart and fall down suddenly.” It is a stretch to use it for something that takes thousands of years to happen.
You have to scratch your head in wonder, when a worst-case scenario is a rise of a couple inches in a lifetime. I have built sand castles at the beach that could withstand waves that tall.
I think we’re witnessing the ‘collapse’ of the CAGW cult.
Ok…well more like it’s agonisingly slow decline!
its agonisingly slow decline…tsk.
Bill Illis says:
June 25, 2014 at 9:47 pm
…
The current interglacial is projected to be the longest one yet. Lasting at least 52,000 years morel and, more likely, 125,000 years. Far northern summer solar insolation will decline by a tiny amount (0.5 W/m2) in the next 2,000 years, leaving it well above the limit needed to melt the snow in the summer on non-glaciated land. It will then go back up again and stay above the limit needed to melt the snow in the summer for the next 50,000 years after this. It will be touch and go at this time, but solar insolation will then increase again after this time, staying high until 125,000 years from now.
Tzedakis in his 2012 paper said that:
“The glacial inception during Marine Isotope sub-Stage 19c, a close analogue for the present interglacial, occurred near the summer insolation minimum, suggesting that the interglacial was not prolonged by subdued radiative forcing.” (my bold)
http://www.nature.com/ngeo/journal/v5/n2/abs/ngeo1358.html
This contradicts your assertion that “subdued radiation forcing” will prolong the current interglacial.
Its a nonlinear system. The absolute values of insolation are not the be-all-and-end-all that you make them out to be.
Note also – why did the MPR happen? We are over the long term in a period of deepening glaciation. From no glaciation, to interglacials with 40k year spacing, to 100k year spacing, to predictably a future of uninterrupted glaciation.
A 125k year interglacial is very unlikely in this context.
Ignoring dbstealey’s C18th take on science…
Tsk Tsk you say
“Given sufficient time –say on the order of decades that you warmists wail about– we most assuredly CAN prevent an asteroid strike.”
Tell us how please ?
Also, we know the orbits of all the large asteroids. Work is ongoing on tracking the smaller ones now – and those would not cause a global disaster. The bigger immediate danger is comets. We might have just a few years warning of an impact from a newly discovered large comet coming in from the outer solar system.
But the risk of that is very small compared to the risk of just allowing CO2 concentration to keep increasing. Stephen Richards – we have control over that – which is my point. Or do you think the rise in concentration since the Industrial Revolution is natural ?
James Abbott:
I am genuinely curious.
At June 26, 2014 at 3:07 am you assert
Please explain
1.
What is the “risk of just allowing CO2 concentration to keep increasing”?
2.
Whether or not the rise in concentration since the Industrial Revolution is natural, how do we “have control over that” when “no systematic analysis has published on the relationship between mitigation and baseline scenarios”?
3.
The fact that nobody knows the relationship between mitigation and baseline scenarios was published by the IPCC in Chapter 2 from Working Group 3 in the IPCC’s Third Assessment Report (2001). Nobody has made such a publication since, so how do you know “we have control over that” when nobody else does?
4.
Why have you not published your unique knowledge of how “we have control over that” when you claim there is “risk of just allowing CO2 concentration to keep increasing” unless – of course – you think the “risk” is trivial?
Thanking you in anticipation of your clarifications
Richard
There seems to me to be a big gap between the atmospheric CO2 “causing” Climate Change, & proving it. The only argument seems to be “but what else can it be?” which has much to be desired on a scientific front, especially when NOBODY has described what the natural variability of climate actually is! Who will hold these AGW/CC idiots to account in the long run, or will they just be handsomely pensioned off into oblivion to be forgotten with the “best available science at the time” meme ringing in our ears? This reminds me of crying witch! Better get the ducking stool ready along with some bundles of sticks for the fire!
James Abbott says:
June 25, 2014 at 5:09 pm
Vercigenitorex – very true. But we have some control over whether the planet continues to warm over the coming centuries but no control at all over a major volcanic eruption or an asteroid strike.
Who is we James? ISIS? The Chinese? Subsaharan Africans? The Yanomami? Popol Vuh? Global Warming is a First World problem dreamed up by half educated socialist globalists who are totally blind to the second and thiird world social, economic, nationalist and religious extremist threats staring them squarely in the face.
“Ah. . . Clem ”
perhaps I am the only other one who knows where that name comes from…..
Reblogged this on This Got My Attention and commented:
Whoa, Nelly! The Greenland icesheet collapsed WITHOUT man-caused global warming 400,000 years ago. How will the alarmists work this into their models?
It would have been illuminating if they had shown data for other interglacials so as to judge the MIS 11 sedimentation events comparatively. To refer to MODELS of anything just diminishes further what they have to say. Who reviewed this for Nature – where all the trouble starts. How long before the politicians latch on to this as “evidence” for a catastrophic future. 0 out of 10 I`m afraid, and hardly scientific.
Teriffic! Now we have empirical data regarding the consequences of global warming and a global MSL rise both 400,000 Ya and 125,000 Ya – two periods remarkable in the fossil record for a complete dearth of global catastrophe and the mass extinction of absolutely nothing.
So the AGW alarmists want us to invest trillions of dollars/euros/yuan/shekels/kroner/etc. in a futile effort to prevent – nothing.
James Abbott says:
June 26, 2014 at 3:07 am
Or do you think the rise in concentration since the Industrial Revolution is natural ?
+++++++++
No, I think the rise of CO2 since the Industrial Revolution is meaningless, except as noted for the added growth of plants.