Research resolves discrepancy in Greenland temperatures during end of last ice age

Study resolves discrepancy in Greenland temperatures during end of last ice age
Bo Vinther prepares an ice core for visual inspection. Credit: Christian Morel

A new study of three ice cores from Greenland documents the warming of the large ice sheet at the end of the last ice age – resolving a long-standing paradox over when that warming occurred.

Large ice sheets covered North America and northern Europe some 20,000 years ago during the coldest part of the , when global average temperatures were about four degrees Celsius (or seven degrees Fahrenheit) colder than during pre-industrial times. And then changes in the Earth's orbit around the sun increased the solar energy reaching Greenland. Beginning some 18,000 years ago, release of carbon from the deep ocean led to a graduate rise in atmospheric carbon dioxide (CO2).

Yet past analysis of ice cores from Greenland did not show any warming response as would be expected from an increase in CO2 and solar energy flux, the researchers note.

In this new study, funded by the National Science Foundation and published this week in the journal Science, scientists reconstructed by examining ratios of nitrogen isotopes in air trapped within the ice instead of isotopes in the ice itself, which had been used in past studies.

Not only did the new analysis detect significant warming in response to increasing atmospheric CO2, it documents a warming trend at a rate closely matching what climate change models predict should have happened as the Earth shifted out of its ice age, according to lead author Christo Buizert, a postdoctoral researcher at Oregon State University and lead author on the Science article.

"The Greenland isotope records from the ice itself suggest that temperatures 12,000 years ago during the so-called Younger Dryas period near the end of the ice age were virtually the same in Greenland as they were 18,000 years ago when much of the northern hemisphere was still covered in ice," Buizert said. "That never made much sense because between 18,000 and 12,000 years ago atmospheric CO2 levels rose quite a bit."

Study resolves discrepancy in Greenland temperatures during end of last ice age
Scientists use a sled to move equipment at the NEEM camp in northern Greenland. Credit: Christian Morel
"But when you reconstruct the history using nitrogen isotope ratios as a proxy for temperature, you get a much different picture," Buizert pointed out. "The nitrogen-based temperature record shows that by 12,000 years ago, Greenland temperatures had already warmed by about five degrees (Celsius), very close to what climate models predict should have happened, given the conditions."

Reconstructing temperatures by using water isotopes provides useful information about when temperatures shift but can be difficult to calibrate because of changes in the water cycle, according to Edward Brook, an Oregon State paleoclimatologist and co-author on the Science study.

"The water isotopes are delivered in Greenland through snowfall and during an ice age, snowfall patterns change," Brook noted. "It may be that the presence of the giant ice sheet made snow more likely to fall in the summer instead of winter, which can account for the warmer-than-expected temperatures because the snow records the temperature at the time it fell."

In addition to the gradual warming of five degrees (C) over a 6,000-year period beginning 18,000 years ago the study investigated two periods of abrupt warming and one period of abrupt cooling documented in the new ice cores. The researchers say their leading hypothesis is that all three episodes are tied to changes in the Atlantic meridional overturning circulation (AMOC), which brings warm water from the tropics into the high northern latitudes.

Past temperature in Greenland adjusted
The revised Greenland temperature history (black curve, grey uncertainties) for the period 18,000 to 10,000 before present. This temperature history is based on temperature interpretation from nitrogen measurements (green curve) and O18 diffusion measurements (red curve). The blue curve is from a previous study, based on nitrogen measurements. Credit: Niels Bohr Institute

The first episode caused a jump in Greenland's air temperatures of 10-15 degrees (C) in just a few decades beginning about 14,700 years ago. An apparent shutdown of the AMOC about 12,800 years ago caused an abrupt cooling of some 5-9 degrees (C), also over a matter of decades.

When the AMOC was reinvigorated again about 11,600 years ago, it caused a jump in temperatures of 8-, 11 degrees (C), which heralded the end of the ice age and the beginning of the climatically warm and stable Holocene period, which allowed human civilization to develop.

"For these extremely abrupt transitions, our data show a clear fingerprint of AMOC variations, which had not yet been established in the ice core studies," noted Buizert, who is in OSU's College of Earth, Ocean, and Atmospheric Sciences. "Other evidence for AMOC changes exists in the marine sediment record and our work confirms those findings."

In their study, the scientists examined three ice cores from Greenland and looked at the gases trapped inside the ice for changes in the isotopic ration of nitrogen, which is very sensitive to temperature change. They found that temperatures in northwest Greenland did not change nearly as much as those in southeastern Greenland – closest to the North Atlantic – clearly suggesting the influence of the AMOC.

"The last deglaciation is a natural example of global warming and climate change," Buizert said. "It is very important to study this period because it can help us better understand the climate system and how sensitive the surface temperature is to atmospheric CO2."

"The warming that we observed in Greenland at the end of the ice age had already been predicted correctly by climate models several years ago," Buizert added. "This gives us more confidence that these models also predict future temperatures correctly."


Explore further

Sun's activity influences natural climate change

More information: "Greenland temperature response to climate forcing during the last deglaciation," by C. Buizert et al. Science, www.sciencemag.org/lookup/doi/ … 1126/science.1254961
Journal information: Science

Citation: Research resolves discrepancy in Greenland temperatures during end of last ice age (2014, September 4) retrieved 27 June 2019 from https://phys.org/news/2014-09-discrepancy-greenland-temperatures-ice-age.html
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Sep 04, 2014
We are in a war. I am brave. You are too. Whatever the price, I shall defend our island planet, whatever the cost may be, I shall fight on the beaches, I shall fight on the landing grounds, I shall fight in the fields and in the streets, I shall fight in the hills; we shall never surrender to the fossil fuel foe. It is no use saying, 'We are doing our best.' You have got to succeed in doing what is necessary. This is our ultimate challenge, the stuff that epic history is made of. Don't stay home and watch it on the tellie. Be there and share. Be among the brave.

People's Climate March: NYC 9.21.14

Sep 04, 2014
Ice cores from both arctic circles and fossilized plants clearly show that CO2 has trailed temps by about 800 years. It also shows that our temps and CO2 levels are at very low levels and that the temps climbed to a high point 10,000 years then dropped significantly.

When modern life evolved over 500 million years ago, CO2 was more than 10 times higher than today, yet life flourished at this time. Then an ice age occurred 450 million years ago when CO2 was 10 times higher than today. The fact that we had both higher temperatures and an ice age at a time when CO2 emissions were 10 times higher than they are today fundamentally contradicts the certainty that human-caused CO2 has any tangible cost.

Since the year of the Hockey Stick (1998) when ppm CO2 levels are lower than they are now, warming as leveled off , proof that CO2 sequestration will have no tangible effects on GW.

Sep 04, 2014
Benni, thanks for illustrating why, exactly, this time it is definitively human-caused. In all the past events, warming added CO2 to the atmosphere gradually over geologic timescales. In the present, CO2 is being added rapidly and is *leading* temperature increase. Thus it must be that humans, adding CO2 to the atmosphere, are driving the current warming trend observed. This warming then, through natural feedback processes, is adding additional CO2 (and methane) to the atmosphere causing reinforcement of the warming pattern.

But you demonstrate precisely the logic that shows us the modern pattern is remarkably different than previously in history. Good on you for seeing anthropogenic climate change for what it is.

(also it might be worth noting that one can't exactly call 500 million years ago "modern" life. "Modern" life, as in the species on the Earth presently, are only adapted to the climate as it has been more recently in geologic history)

Sep 04, 2014

When modern life evolved over 500 million years ago, CO2 was more than 10 times higher than today, yet life flourished at this time. Then an ice age occurred 450 million years ago when CO2 was 10 times higher than today. The fact that we had both higher temperatures and an ice age at a time when CO2 emissions were 10 times higher than they are today fundamentally contradicts the certainty that human-caused CO2 has any tangible cost.



Nothing alive today is remotely like anything alive 500 million years ago, idiot. How were the temperatures in the Ordovician? Well, the seas were about 45 deg. C, which would kill pretty much everything alive in the ocean today.

Oh, and that end of Ordovician ice age? How'd that work out again? The 2nd worst mass extinction event in Earth history? Yeah, climate change is awesome, fucktard.

Sep 04, 2014
..........and it's the ones who are the most challenged by a differential equation they can't solve who have the least trouble with profanity & vulgarity.

Sep 04, 2014
Nothing alive today is remotely like anything alive 500 million years ago, idiot. How were the temperatures in the Ordovician? Well, the seas were about 45 deg. C, which would kill pretty much everything alive in the ocean today.
--supaturd
Wow!! Were you dropped as a baby, or just born special?

Sep 05, 2014
Benni, thanks for illustrating why, exactly, this time it is definitively human-caused. In all the past events, warming added CO2 to the atmosphere gradually over geologic timescales. In the present, CO2 is being added rapidly and is *leading* temperature increase..

Exactly! During the previous long timescales that earth's natural temperature fluctuations occurred, enough CO2 would be eventually released during warming phases to then sustain the warm cycle for extended periods. That's how it worked before we came along.

Now we're jump-starting the effect, with the obvious result of an unprecedented rate of warming. This is NOT how it naturally happened in the past.

Sep 05, 2014
Nothing alive today is remotely like anything alive 500 million years ago, idiot. How were the temperatures in the Ordovician? Well, the seas were about 45 deg. C, which would kill pretty much everything alive in the ocean today.
--supaturd
Wow!! Were you dropped as a baby, or just born special?


There you go ignoracle! You figured out how to use question marks! Awesome.

At this rate your IQ should be in the double digits in 10,000 years or less.

Keep up the good work!

Sep 05, 2014
Oh! If it ain't rockturd.
I can't believe your mummy let you out of your cesspool 2 days in a row.
I guess she came to terms with leaving the baby at the hospital and bringing the turd home.

Sep 05, 2014
Oh! If it ain't rockturd.
I can't believe your mummy let you out of your cesspool 2 days in a row.
I guess she came to terms with leaving the baby at the hospital and bringing the turd home.


Feel free to believe whatever you wish if it bolsters your fragile and ephemeral ego!

Have you ever considered seeing a mental health professional to address your obsession with shit? Perhaps it's just another symptom of your brain wasting disease?

Sep 05, 2014
@full_disclosure

Are you certain you don't have 5 or 6 words of wisdom to share with us as you normally do or does it take you a few days to process those short sentences?

Sep 06, 2014
Now I'm going to try to turn off the comments again because I am sick of them. The comments here are exactly why this site has been ruined by lack of oversight. They won't stay turned off when I set them to 'off'. They also won't stay at 5. Eventually I will find another science site, if there is no way to keep them turned off. Too bad. I've read this one for years. The comments used to be informative. They added a lot to the articles. But by now, with trolling and insults out of control, they are a prime example of how sites devolve, and cheap bad stuff drives out good quality.

Sep 06, 2014
and it's the ones who are the most challenged by a differential equation they can't solve who have the least trouble with profanity & vulgarity.
@Benni
and it is fascinating that a nuclear engineer with such competent math skills would be unable to comprehend the complex climate science as it is a simple matter of sitting down with the study and working out the math and showing where it is wrong in the study...
something which you have yet to be able to accomplish

now quit sticking your nose into the air and feigning mathematical superiority while being incapable of reading a study that is widely available http://www.scienc...full.pdf

and if you cannot read the study, create a throwaway gmail/yahoo/hotmail or other e-mail account and post it and I will SEND it to you from AAAS (which is SAFE if you have anti-virus, anti-malware etc and use the e-mail's anti-virus as well)


Sep 06, 2014
But by now, with trolling and insults out of control, they are a prime example of how sites devolve, and cheap bad stuff drives out good quality
@dollymop
Whereas you have a point about cheap bad stuff driving out the good...

you also have the power to help FIGHT AGAINST anti-science posts as well

Antigorical regularly trolls... how often do you downvote or report his posts?

Benni makes grandiose claims but refuses to provide links/proof from reputable peer reviewed sources which impact the subject at hand...
Zephir, cantdrive, the EU acolytes etc posts pseudoscience
Verkle ignores all science for faith

you have the ability to correct the problem by at least voting etc if you are not comfortable refuting science
And the ones posting real science like Runrig deserve an upvote
You can also talk to the site management with the CONTACT link below (at the bottom of every page)

don't just leave... try to actively support the site and get rid of the trolls/pseudoscience

Sep 06, 2014
@ dollymop.... Why does it matter if the comments are on or off...They are at the bottom of the page after the related stories section, does your computer force you to read them ?? If you don' like them, don't read them ! I am not saying I agree with the comments, but to me its like some one complaining they do not like a certain radio station or TV channel, you have the option of avoiding !

Sep 06, 2014
Now I'm going to try to turn off the comments again because I am sick of them. The comments here are exactly why this site has been ruined by lack of oversight. They won't stay turned off when I set them to 'off'. They also won't stay at 5. Eventually I will find another science site, if there is no way to keep them turned off. Too bad. I've read this one for years. The comments used to be informative. They added a lot to the articles. But by now, with trolling and insults out of control, they are a prime example of how sites devolve, and cheap bad stuff drives out good quality.

You can set a mark point to screen the idiots out ... then just read the likes of me, capt, Thermo, How, etc for sensible, scientific comments.

Sep 07, 2014
@dollymop
I agree with the Captain, stay and fight back to push the pseudoscience fanboys off the site or at least point and laugh at them...

Sep 07, 2014
Nothing alive today is remotely like anything alive 500 million years ago, idiot. How were the temperatures in the Ordovician? Well, the seas were about 45 deg. C, which would kill pretty much everything alive in the ocean today.

Oh, and that end of Ordovician ice age? How'd that work out again? The 2nd worst mass extinction event in Earth history? Yeah, climate change is awesome, fucktard.


You realize the temperatures then were caused by the fact the radiological energy from inside the Earth was greater by about 8 kelvin or so relative to the present day sub-surface equilibrium point from solar input vs geological inputs? This point is currently several hundred feet underground in most places, but if it was 8 kelvin hotter, the equilibrium point might will be at the surface nearly everywhere.

Increased temperatures would have very little relationship to Carbon Dioxide if the internal temperature was that much warmer (you can do some math with decay rates, etc).

Sep 07, 2014
I thnk the fields of Paleontology and Geology could benefit if they made a rule that temporarily banned all papers from drawing upon any present-day so-called "knowledge" of the field, and required everyone to start back over from a point of presumed ignorance, with no prior knowledge or assumptions. After at least several decades, or a generation or two, we could then compare notes to the last time around for the field, and see if the "new geology" says the same thing as the "old geology".

Facts are facts, but interpretations of facts are another thing.

Today, most "facts" are actually not facts at all, but rather "interpretations" of other facts, or interpretations of other interpretations.

For example, in the article above, they found the data did not agree with the carbon model, so they went back and found some "facts" (nitrogen record based on present day assumptions relative to the... carbon model) to support the ...carbon model.

Circular reasoning =/= facts.

Sep 08, 2014

You can set a mark point to screen the idiots out ... then just read the likes of me, capt, Thermo, How, etc for sensible, scientific comments.

Best joke I've read on physorg.... sensible, scientific comments...ha..ha...good one. Thanks runrig, me thinks someone missed their calling.

Sep 09, 2014

You can set a mark point to screen the idiots out ... then just read the likes of me, capt, Thermo, How, etc for sensible, scientific comments.

Best joke I've read on physorg.... sensible, scientific comments...ha..ha...good one. Thanks runrig, me thinks someone missed their calling.


Anti: I should have just said "scientific comments".

Sep 09, 2014

You can set a mark point to screen the idiots out ... then just read the likes of me, capt, Thermo, How, etc for sensible, scientific comments.

Best joke I've read on physorg.... sensible, scientific comments...ha..ha...good one. Thanks runrig, me thinks someone missed their calling.


It looks like its you who missed your calling.
http://en.wikiped...plewhite

NOM
Sep 09, 2014
Antigorical regularly trolls... how often do you downvote or report his posts?

What good does reporting do?

I think physorg has decided to encourage the trolls, rather than remove them. Otherwise how could Zephyr still be openly posting his AWK crap?
verkle trolls anything that mentions evolution with his fundy drivel, cantthink85 trolls anything that mentions the word plasma with his EU nonsense, rygtard and freefromthinking troll anything and everything with their political rubbish, Lex Talonis uses the word "fuck" as punctuation. There are countless other posting nothing but pseudoscience. Yet all ofo this is supposedly against the site terms of use.

Reporting these posts hasn't changed anything. So I thnk physorg has decided to be a pseudoscience and anti-science site.

Sep 09, 2014
"Reporting these posts hasn't changed anything. So I thnk physorg has decided to be a pseudoscience and anti-science site."

Physorg is interested in as much traffic as they can garner. The trolls are click bait.


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