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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So that’s what happened to Atlantis, them and their dirty carbon fuel habits.
At least they are now talking about the cores being a LOCAL record. The quality of the research is now getting better thanks to some very smart people taking the bad science to the woodshed.
So much for the overuse of the word “unprecedent” in AGW scaremonging headlines.
I have commented on this blog before about the super-interglacial of ~400,000 years ago, in which the southern dome of the Greenland Ice Sheet largely disappeared. Same apparently happened some 800,000 years ago. Scientists disagree as to whether the current interglacial, the Holocene, will last as long as MIS 11. I went round the mulberry bush with Lord Monckton on the issue of the likely time remaining for the Holocene.
Based upon orbital parameters, the now ~11,000 year-old Holocene could go super, like MIS 11’s tens of thousands of years in duration, but against that forecast is the fact that for at least the past 3000 years, earth’s climate has been in a cooling trend, which if simply extrapolated would get us back to glacial conditions in a few thousand years.
But IMO this study is misleading to speak of “collapse”, if that is its actual language. The melting occurred over a very long period of temperatures higher than now. It was a gradual diminution, not a prompt collapse due to suddenly elevated temperature.
If the Holocene lasts as long as MIS 11, then the southern dome will probably melt at least as much, ie partially, as it did during the previous interglacial, the Eemian of MIS 5, which was warmer & lasted longer than the Holocene has to date, but not as long as MIS-11.
milodonharlani says:
June 25, 2014 at 1:55 pm
………
But IMO this study is misleading to speak of “collapse”, if that is its actual language. The melting occurred over a very long period of temperatures higher than now. It was a gradual diminution, not a prompt collapse due to suddenly elevated temperature.
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I believe we remember a recent similar situation resulting from the particular meaning of that same word at the other end of the planet.
Gosh darn that Neanderthal man and his Flintstonemobiles!
Greenland is one of my favourite anti-CAGW examples.
Greenland had a permanent Viking settlement for over 500 years (during the medieval warm period), and there are remains of graveyards and structures under ice sheets today.
They were driven out by (you guessed it!) Climate Change.
spdrdr says:
June 25, 2014 at 2:51 pm
Dunno about under ice sheets, but still under permafrost, yeah, you betcha!
““This may give us a better sense of what may happen in the future as temperatures continue rising,” Carlson added.”
Like over the past 17 years, Anders? No, temps have fallen. 80 years? No, temps have fallen. How about over the past 1000 years? Fallen. 2000 years? Fallen. 3300 years? Fallen. 8000 years? Fallen. The entire interglacial period up to the present day? A >10,000 year cooling trend, the warm periods becoming progressively cooler, and the intervening cooler periods, progressively colder still, the last one the coldest the planet has been since the last glacial period.
Kenw says:
June 25, 2014 at 2:13 pm
“Collapse” has joined the unprecedented lexicon of how to lie using words as well as statistics.
Taphonomic says:
June 25, 2014 at 2:25 pm
Gosh darn that Neanderthal man and his Flintstonemobiles!
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We have the previously unnoticed Neanderthal Industrial Age to blame for partial GIS melting during the Eemian, and it’s H. heidelbergensis’ fault for turning forests into spears and burning them down to cook Irish elk and for warmth without tailored (or maybe any) clothing for the total meltdown of MIS 11. And 800,000 years ago more archaic Homo subspecies had recently invaded Europe. Coincidence? I think not!
Sorry, it is permafrost. I cannot tell the difference between permafrost and an ice sheet, being a tropical sun-lover…
spdrdr says:
June 25, 2014 at 3:12 pm
Good on ya, then!
Color and consistency are give aways, should you ever chose to visit Arctic climes.
Just tell them that Leif and Willis don’t reckon the ‘sun’ has any impact on the earth’s climate.
That should put them in their place!
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 ?
James Abbott says:
June 25, 2014 at 4:18 pm
So far CO2 increase has been a very good thing. Another 100 ppm or so would be even better for plants & other living things.
The southern dome thawed over tens of thousands of years of elevated temperature. A century of at most one degree higher than during 1977 to 2006 won’t do it.
milodonharlani you put your faith in a rise of only 1C.
We have warmed 0.6C in the last 40 years (NASA GISS).
Also, why do you assume that the elevated temperature will only last a century ?
Yes if the Greenland Ice sheet or Antarctica melted it would be catastrophic. It would also be catastrophic if there were another Toba event or a large asteroid struck the planet.
” They acknowledge the need for more widespread coring data and temperature reconstructions.”
…as always, more funding required.
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.
http://nsidc.org/greenland-today/
James Abbott says:
June 25, 2014 at 4:35 pm
We have warmed 0.6C in the last 40 years (NASA GISS).
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James..we warmed for the first 30 years because NASA/GISS erased the cooling trend and used a different set of temperature numbers to show temps rising…they did that in 2000…we have not warmed at all since they did that….
..since 2000 there has been no global warming
Jam Abbot says:
“But we have some control over whether the planet continues to warm over the coming centuries”
Yes, “Settled Science”.
More Justification Needed for Limiting CO2 Emissions
The scientific basis for limiting CO2 emissions is summarized by two sentences in the “Summary for Policymakers” of the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4). Both are in a paragraph from Section 2, “Causes of change” of AR4.
“During the past 50 years, the sum of solar and volcanic forcings would likely have produced cooling. Observed patterns of warming and their changes are simulated only by models that include anthropogenic forcings.”
The term “forcings” is the climatologist’s way to quantify the impact of potential contributors to global temperatures in their computer models. Positive and negative forcings denote global warmers and global coolers respectfully.
The first sentence reflects the IPCC climatologist’s assessment that the combination of the sun and volcanic activity would have reduced global temperatures. When they used their estimated “cooling” forcings in the computer model the results, not surprisingly, predicted slight declines in global temperatures over the last 50 years.
As the second sentence explains, rather than “adjust” the sun and volcanic activity forcings, the climatologists assumed the computer model failure was due to a lack of “anthropogenic” green house gases (GHG) primarily CO2 forcings. Raising the computer model “predicted” temperatures to the measured levels required GHG forcings 10 times climatologists estimates for the Sun. It is this level of forcings that makes global temperatures so sensitive to increased GHG emissions and has led to billions spent attempting to reduce their emissions.
It’s not clear why climatologists concluded any potential warming from the Sun was “likely” more than offset by the cooling effects of volcanic ash during the last 50 years. The combination of the two has been largely responsible for many warming and cooling periods for hundreds of thousands of years. Global temperatures during the Medieval Warming Period in 1000-1100 AD were at least as high as current levels. The MWP was followed by cooling, presumably due to some combination of reduced energy from the sun and/or more volcanic ash that lasted until the end of the Little Ice Age of the mid 1800’s.
Much of the temperature increase after 1850 occurred prior to significant GHG emissions. What led climatologists to conclude the combination of the Sun and volcanic activity would reduce rather than increase global temperatures during the last 50 years? Why assume the increase was due to relatively small changes to atmospheric CO2 levels from ~ .031% to .036% during that time period? Particularly since subsequent increases to ~.040% recently haven’t resulted in any significant additional global warming?
The only link between atmospheric CO2 levels and global temperatures was an early assessment (Al Gore (?)) showing global temperatures tended to increase, purportedly in response to higher CO2 levels. However, an article recently published in “Climate of the Past” about East Antarctic ice core studies showed CO2 levels lagged temperature changes by 500 to 5000 years. Obviously increasing CO2 can’t cause global warming if it occurs after the increase.
In conclusion, the hundreds of billions already spent limiting GHG will be dwarfed by the costs associated with future efforts. Climatologists need to do more to justify the need to do so beyond “During the past 50 years, the sum of solar and volcanic forcings would likely have produced cooling.”
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.
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Given sufficient time –say on the order of decades that you warmists wail about– we most assuredly CAN prevent an asteroid strike.
How many billions are you willing to sacrifice to your CO2 monster?