Ice sheet collapse triggered ancient sea level peak

Ice sheet collapse triggered ancient sea level peak: ANU media release
Speleotherms from Soreq Cave, Israel. Credit: Eelco Rohling

An international team of scientists has found a dramatic ice sheet collapse at the end of the ice age before last caused widespread climate changes and led to a peak in the sea level well above its present height.

The team found the events 135,000 years ago caused the planet to warm in a different way to the end of the most recent ice age about 20,000 to 10,000 years ago.

The findings will help scientists understand the processes that control Earth's dramatic climate changes, said the leader of the study, Dr Gianluca Marino of The Australian National University (ANU).

"We knew the sea level had overshot its present levels during the last interglacial period, but did not know why. Now we for the first time can explain the processes that caused the sea levels to exceed the present levels," said Dr Marino, from the ANU Research School of Earth Sciences.

"Ice-age cycles may superficially look similar to one another, but there are important differences in the relationships between melting of and global climate changes."

The team, which includes researchers from ANU as well as the Universities of Southampton and Swansea in the UK, has published their findings in Nature.

At the end of an ice age the continental ice sheets, ocean, and atmosphere change rapidly. Scientists have previously only been able to reconstruct in detail the changes at the end of the last ice age.

Ice sheet collapse triggered ancient sea level peak: ANU media release
Dr. Gianluca Marino and Dr. Katharine Grant load a sediment core into an X-ray fluorescence scanner. Credit: Stuart Hay, ANU

"We have compared the fluctuations at the end of an earlier ice age, and we found that the patterns were different," said co-author Professor Eelco Rohling, from both ANU and the University of Southampton.

"At the end of the older ice age, 135,000 years ago, we found that a dramatic collapse of the Northern Hemisphere ice sheets into the North Atlantic Ocean suppressed the ocean circulation and caused cooling in the North Atlantic."

"North Atlantic cooling was counterbalanced by Southern Ocean warming that then destabilised Antarctic land ice, causing a continuation of melting that eventually drove rise to several meters above the present," he said.

Ice sheet collapse triggered ancient sea level peak: ANU media release
Drilling aboard Joides Resolution research shi is shown. Credit: Markus Fingerle & IODP/TAMU

This is very different from the end of the last , said Dr Marino.

"The northern hemisphere collapse and did not occur at the same time, and that caused much less warming in Antarctica," he said.

The team used precisely-dated cave records and marine sediments from the Mediterranean region to reconstruct the sequence of changes in all critical parameters.


Explore further

Evolution of the Antarctic ice sheet

More information: Bipolar seesaw control on last interglacial sea level, Nature, DOI: 10.1038/nature14499
Journal information: Nature

Citation: Ice sheet collapse triggered ancient sea level peak (2015, June 10) retrieved 18 August 2019 from https://phys.org/news/2015-06-ice-sheet-collapse-triggered-ancient.html
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Jun 10, 2015
More pieces of info to be compiled into a more complete history of our Earth, and it appears that there is an alteration of N and S hemisphere involvement in the climate result of the time.

Jun 11, 2015
There is no information about the time scales of the collapse, the sealevel rise, the rapid changes involved. Tens of years, hundreds or thousands?

It is scandalous that public funded research of such global importance is locked up behind behind a pay wall. Its a shame.

Jun 11, 2015
It is scandalous that public funded research of such global importance is locked up behind behind a pay wall.

The paywall is because the PUBLISHERS are private companies that want to make a buck. They are not publicly funded.
If you want the article just ask the authors (nicely). I'm pretty sure they'll give you an electronic copy.
There is no information about the time scales of the collapse,

Look at the last image that is frely available on the link to the article.

And please - before you get all riled up about something in the future: make sure that you're raging against the right target.

Jun 11, 2015
Sorry, I did not name any target and did certainly not rile against the authors. Maybe its your assumption but not my intent. I also stated that THE RESEARCH IS PUBLICLY funded and I know that the publisher in question is a private company. I agree that publishers should be able to make money by publishing, but I don't agree with the way they do profit from public funded research. They neither pay the authors nor the peer reviewers and in many cases contribute little in editing and on top ask hefty subscription fees from the institutions paying the authors. I think that something is wrong here and and I'm certainly not alone in this.

No lecturing is needed here please, but thanks for the hint about the image. :-)

Jun 11, 2015
but I don't agree with the way they do profit from public funded research.

How is that different from any other publication?
If you buy an auto magazine then the publisher benefits from the research an development that went into the cars that they are reporting about - they don't pay for that, either.
You pay for the printing (i.e. making the stuff available to you in concentrated form) - not the subject matter. If you have an issue with that then you should probably have an issue with all paid for forms of information dissemination (pay TV, pay news-sites on the internet, .. ) .

A thing that is a legitimate gripe against publishers of scientific articles is: The authors of the papers aren't paid anything (and have to pay in some cases to have specialty wishes fulfilled - like color instead of black/white graphs). They do this on their own dime/time (including the formating, BTW).

Jun 11, 2015
A thing that is a legitimate gripe against publishers of scientific articles is: The authors....

Q.E.D. congratulations
and
http://en.wikiped...g_reform

Jun 11, 2015
First we have a "crusade" against the Element Chlorine ( ozone depletion....snicker, giggle). Now we have a "crusade" against Carbon ( CO2 induced Global Warming....guffaw). Now "ozone depletion" and the "greenhouse effect" are fighting one another. This is like the centuries-old feud between Sunni and Shia. And makes about as much sense. Religion from Medieval Times. Religion of the Modern Times (it ain't "Science"). In both cases, it's religion mixed with politics.

Jun 11, 2015
Q.E.D. congratulations

Sure. I'd like to see the publication channels to be organized differently (as I have been subject to that problem first hand).
There are some approaches (arxiv, open science, etc.). They are laudable, but there are some things that still need to be addressed which haven't been conclusively figured out:

1) Peer review. Who organizes peer review and makes sure that crank papers are thrown out? While not prefect this is something the publishers of scientific articles currently do (the organization - not the peer review itself. That is done by peers in the field. Again for no pay, BTW. Which has its up and down sides. Upside: you get to see papers as a peer reviewer way earlier than anyone else. Downside: you have to find time to do peer review. It's a quite time consuming process).

2) Projects funded jointly with industry partners (which, today, is basically all projects). The clear cut case of "public funding - public data" is a very small minority.

Jun 11, 2015
( CO2 induced Global Warming....guffaw)
@richard
by all means, please show the studies which have refuted the known details and physics of the CO2/WV feedback cycle (measured, observed, modeled and validated by numberous other studies)

science follows the evidence, dick... it is not about "belief" or "faith" in any way, shape or form

your arguments about AGW are all linked to politics, religion and conspiracy - you have NOT shown a scientific basis for your disbelief

this is demonstrated in your comments

now, i am not saying that political parties aren't trying to utilize the science for their personal benefit - politicization of the science

that will happen REGARDLESS of what is being done
(example- see: creationists - their argument is designed to gain political favor so that they can get into the education program because there is NO science involved - even the court can see that: McLean vs Arkansas)

Jun 11, 2015
The earth has been cooling since 1980.
My proof?
Texas weather. There has never been a warmer summer in my life (58 years).
Last year was routed as the warmest ever. Not.
Why isn't global warming global?
Heat transfer and thermodynamics do not allow something to become colder because it is warmer. Heat flows like water. From high energy to low. There has been no global warming for almost twenty years now. Throwing out the data one doesn't like does not improve the arguments for warming. The climate of the Earth changes. All things perish. Humanity is nature. Want to change it? Reduce the multitudes of humanity. Exercise some control on breeding. Not likely. We are humans. When we no longer behave the way we do there shall be no more humans. The solution to 'saving' the world is human extinction. To 'preserve' it requires controls over human behavior that the race shall not accept. Control builds resentment builds revolt. It is inevitable. The elite doom themselves.

Jun 11, 2015
The earth has been cooling since 1980
@odin
except that we can prove the EARTH has been warming

http://www.woodfo...60/trend

There has been no global warming for almost twenty years now
debunked with the above link
that is before the data noise was reduced

continuing to repeat a lie ad nauseum doesn't make it any more true the last time as it was the first time

you were proven wrong before, a basic search of historical temps proves you wrong now

(unless, of course, you use Koch sponsored anti-science sites or political arguments. there is NO SCIENTIFIC evidence supporting your conjecture - even the noisy data says you are wrong)

Jun 11, 2015
Why isn't global warming global?
@odin
1- you are confusing WEATHER with CLIMATE
2- global temps are taken from (yup- you guessed it: the GLOBE! Everywhere!) and then the average is taken from the data
3- global warming can also produce localised cooling in winter: see Francis et al in the following links:

http://marine.rut..._pub.pdf

http://iopscience...4005.pdf

Francis 40 min video:
https://www.youtu...m9JAdfcs

Francis short but sweet vid:
https://www.youtu...wJg4Ebzo

The climate of the Earth changes. All things perish. Humanity is nature
and we also know that humans CAN change the climate (Lacis et al)
we can differentiate between natural and man-made CO2

http://www.bitsof...ng-5732/


Jun 15, 2015
So why is man being blamed now for something that has happened many times in the past before modern man. It sure seems like climate changes are a natural part of Earths history.

If a shop owner sees someone stealing and that person says "This is my first day in this town, you surely have had thousands of thefts from your shop before and it was never me, so you have no reason to accuse me now", would you accept that argument?

Many events have multiple possible causes. People have died from many causes, but none have died yet from someone hacking into a self-driving car. That doesn't mean such hacking can't cause death. The same applies to global warming. That global warming can happen without human intervention doesn't prevent human intervention from being a possible cause. And the reason why human activity is being blamed this time round is that there is evidence.

Jun 15, 2015
The earth has been cooling since 1980.
I offer you a bet on that. If you are sure the Earth is cooling, you should be willing to bet on the next 10 to 20 years being cooler on average than the previous 20. What do you think of $1000 invested in a joint account to which only the winner will have access when the time is up? I have offered that bet twice before on this site when people claimed the Earth was cooling, but nobody took me up on it.

Jun 16, 2015
Just a word on dating. Including warmer interstadia, the latest ice-age is generally placed between 12,000 and about 115,000 yr BP. We live in the closing stages of the latest interglacial period, somewhat cooler than the previous interglacial between about 115,000 and 130,000 years ago. This study confirms what ice-cores have suggested: that the last interglacial differed from the current by virtue of more ice-sheet melting, higher ocean levels, and altered ocean circulation. In that interglacial, much of the Greenland ice-sheet was ablated and a Greenland summer would actually have been green.

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