Researchers look to the Southern Ocean for an explanation of the 'Last Glacial Maximum'

Jun 02, 2014 by Genevieve Wanucha
An artist's rendering of ice age Earth at glacial maximum. Credit: Ittiz/Wikimedia Commons

The paleoclimate record for the last ice age—a time 21,000 years ago called the "Last Glacial Maximum" (LGM)—tells of a cold Earth whose northern continents were covered by vast ice sheets. Chemical traces from plankton fossils in deep-sea sediments reveal rearranged ocean water masses, as well as extended sea ice coverage off Antarctica. Air bubbles in ice cores show that carbon dioxide in the atmosphere was far below levels seen before the Industrial Revolution.

While ice ages are set into motion by Earth's slow wobbles in its transit around the sun, researchers agree that the solar-energy decrease alone wasn't enough to cause this glacial state. Paleoclimatologists have been trying to explain the actual mechanism behind these changes for 200 years.

"We have all these scattered pieces of information about changes in the ocean, atmosphere, and ice cover," says Raffaele Ferrari, the Breene M. Kerr Professor of Physical Oceanography in MIT's Department of Earth, Atmospheric and Planetary Sciences, "and what we really want to see is how they all fit together."

Researchers have always suspected that the answer must lie somewhere in the oceans. Powerful regulators of Earth's climate, the oceans store vast amounts of organic carbon for thousands of years, keeping it from escaping into the atmosphere as CO2. Seawater also takes up CO2 from the atmosphere via photosynthesizing microbes at the surface, and via circulation patterns.

In a new application of ocean physics, Ferrari, along with Malte Jansen PhD '12 of Princeton University and others at the California Institute of Technology, have found a new approach to the puzzle, which they detail in this week's Proceedings of the National Academy of Sciences.

Lung of the ocean

The researchers focused on the Southern Ocean, which encircles Antarctica—a critical part of the carbon cycle because it provides a connection between the atmosphere and the deep ocean abyss. Ruffled by the winds whipping around Antarctica, the Southern Ocean is one of the only places where the deepest carbon-rich waters ever rise to the surface, to "breathe" CO2 in and out.

The modern-day Southern Ocean has a lot of room to breathe: Deeper, carbon-rich waters are constantly mixing into the waters above, a process enhanced by turbulence as water runs over jagged, deep-ocean ridges.

But during the LGM, permanent covered much more of the Southern Ocean's surface. Ferrari and colleagues decided to explore how that extended sea ice would have affected the Southern Ocean's ability to exchange CO2 with the atmosphere.

Shock to the system

This question demanded the use of the field's accumulated knowledge of ocean physics. Using a mathematical equation that describes the wind-driven ocean circulation patterns around Antarctica, the researchers calculated the amount of water that was trapped under the sea ice by currents in the LGM. They found that the shock to the entire Earth from this added ice cover was massive: The ice covered the only spot where the deep ocean ever got to breathe. Since the sea ice capped these deep waters, the Southern Ocean's CO2 was never exhaled to the atmosphere.

The researchers then saw a link between the sea ice change and the massive rearrangement of ocean waters that is evident in the paleoclimate record. Under the expanded sea ice, a greater amount of upwelled deep water sank back downward. Southern Ocean abyssal water eventually filled a greater volume of the entire midlevel and lower ocean—lifting the interface between upper and lower waters to a shallower depth, such that the deep, carbon-rich waters lost contact with the upper ocean. Breathing less, the ocean could store a lot more carbon.

A Southern Ocean suffocated by sea ice, the researchers say, helps explain the big drop in atmospheric CO2 during the LGM.

Dependent relationship

The study suggests a dynamic link between sea-ice expansion and the increase of water insulated from the atmosphere, which the field has long treated as independent events. This insight takes on extra relevance in light of the fact that paleoclimatologists need to explain not just the very low levels of atmospheric CO2 during the last , but also the fact that this happened during each of the last four glacial periods, as the paleoclimate record reveals.

Ferrari says that it never made sense to argue that independent changes drew down CO2 by the exact same amount in every ice age. "To me, that means that all the events that co-occurred must be incredibly tightly linked, without much freedom to drift beyond a narrow margin," he says. "If there is a causality effect among the events at the start of an ice age, then they could happen in the same ratio."

"This study is an elegant, straightforward explanation that pulls all these pieces together into one place like no one has managed to do before," says Daniel Sigman, a professor of geological and geophysical sciences at Princeton, who was not involved in the study.
Sigman, who tries to understand carbon fluxes in the last ice age, says that this new framework narrows his focus to a smaller range of possibilities. "What it really does is tune me in to the sea ice and biochemical conditions that I need to see at the Southern Ocean's surface for the full CO2 drop to be realized."

Explore further: Study suggests large waves may have bigger role in breaking up polar sea ice than thought

More information: "Antarctic sea ice control on ocean circulation in present and glacial climates," by Raffaele Ferrari et al. www.pnas.org/cgi/doi/10.1073/pnas.1323922111

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User comments : 26

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ubavontuba
1.4 / 5 (11) Jun 02, 2014
LOL, I can't help but think that top image, of an icebound earth, looks like an AGWite's dream come true.

Maggnus
4.3 / 5 (11) Jun 02, 2014
This article gives a good account of the opposite problem we face now, too much co2 being drawn out of the atmosphere. It is interesting that they detail the exchange occurring in the southern oceans, given there is evidence a similar mechanism is going on in the same area now, only involving heat transport to the deep ocean.

Interestingly enough, Ubamoron actually brought that particular study to my attention, although as usual he really didn't understand it nor its implications. I don't suppose you remember and could maybe repost that one could you stupid? Probably not, you probably have no clue what I'm talking about, given you actually had no clue what the article you linked to said.

This site is pretty good: http://oceans.mit..._134.pdf The current "record" sea ice extent probably can't extend to the area of greatest overturning due to those very strong winds.
ubavontuba
1.1 / 5 (11) Jun 03, 2014
Maggnus, you aren't a very nice person, are you?

It appears the failure of your doomsday cult prophecies is likely inducing a defensive stress hysteria, which subsequently traps you in a deviancy amplification spiral. That is, the more the facts line up against you, the worse you get as a human being!

Maggnus typifies the AGWite deviancy amplification spiral.

Now try asking again in a civilized fashion, and maybe I'll give you what you asked for.

ubavontuba
1.7 / 5 (11) Jun 03, 2014
...or maybe not. It depends on how civil you can be.
rockwolf1000
3.7 / 5 (9) Jun 03, 2014
...or maybe not. It depends on how civil you can be.


Provide proof that you deserve to be treated with civility.
ryggesogn2
2 / 5 (8) Jun 03, 2014
the deep ocean abyss.

How deep is that?
I have been trying to find the median depth of the ocean, but all that I have found on-line is mean.
full_disclosure
1.4 / 5 (10) Jun 03, 2014
Maggnus, you aren't a very nice person, are you?

It appears the failure of your doomsday cult prophecies is likely inducing a defensive stress hysteria, which subsequently traps you in a deviancy amplification spiral. That is, the more the facts line up against you, the worse you get as a human being!

Maggnus typifies the AGWite deviancy amplification spiral.

Now try asking again in a civilized fashion, and maybe I'll give you what you asked for.



Sorry I down voted you Uba…was accidental…Maggnus is Vendicar….just too frightened to post under that name these days…decapitation must be a no no under the new management.
Maggnus
4.5 / 5 (8) Jun 03, 2014
Sorry I down voted you Uba…was accidental…Maggnus is Vendicar….just too frightened to post under that name these days…decapitation must be a no no under the new management.

Ah, little full-diaper has decided to come out of the shadows! And now I am Vendicar too! Let's see now, I 've been accused of being so many other people, I lose track. Deepsand, Caliban and Vendicar all in the last week.

How about you toddle off again little full-diaper, the adults here (I even include Ubamoron in that group) are trying to have a conversation. Thats a good little moron!
Maggnus
4.5 / 5 (8) Jun 03, 2014
the deep ocean abyss.

How deep is that?
I have been trying to find the median depth of the ocean, but all that I have found on-line is mean.
It varies a lot, such that the mean is usually given when you search for an overall number. Average depth is about 2.65 miles (4.3KM). This gives an overview: http://oceanservi...pth.html
Caliban
4.5 / 5 (8) Jun 03, 2014
LOL, I can't help but think that top image, of an icebound earth, looks like an AGWite's dream come true.


And it WOULD BE a dream come true for you, ubybooby --and your very fondest, too!

But dreams are dreamt to be shatterd, ubybooby, as this is a perfect example of the NEGATIVE correlation between atmospheric CO2/GHG content and average global temperatures.

By the way --how's that Northern Hemisphere snow and ice increase looking these days?

Have you recently visited the NSIDC?

Or have they fallen out of favor with you, since the yearly, seasonal(aka, "weather") average and extent data can no longer be claimed by you as support for a downward surface temperature trend?

Are the Colorado glaciers still growing in mass and extent?

Tell us, O ubybooby -please?

Maggnus
4.2 / 5 (10) Jun 03, 2014
Are the Colorado glaciers still growing in mass and extent?

Tell us, O ubybooby -please?

Hahah I forgot about this one! He argued for DAYS that that one year where the mass loss was less than the yearly mass lost in each of the previous 10 years was a sign of temperatures turning around.The fact it was still losing mass and that it was the amount of mass it lost was what was less completely flew over his head! I still laugh at that one!

Don't forget though, Uba thinks we can grow food in deserts! The fact that we can irrigate some small areas of desert means, in his mind, that deserts are open for cultivation. Hope he's right for the sake of the SW US.

I wish he would move into the middle of one with a few seeds for a year. I'll even pitch in a 3 month supply of water.
ryggesogn2
1 / 5 (4) Jun 03, 2014
the deep ocean abyss.

How deep is that?
I have been trying to find the median depth of the ocean, but all that I have found on-line is mean.
It varies a lot, such that the mean is usually given when you search for an overall number. Average depth is about 2.65 miles (4.3KM). This gives an overview: http://oceanservi...pth.html

I already know this.
What's most important is the median. Half the water is below this depth.
I you want to use the mean, then half the ocean is below 4 km.
What is the mass of water that does NOT circulate?
Maggnus
4.1 / 5 (9) Jun 03, 2014
I already know this.
What's most important is the median. Half the water is below this depth.
I you want to use the mean, then half the ocean is below 4 km.
What is the mass of water that does NOT circulate?
You could work it out if you really want to. I'm curious though, what do you think the median is going to tell you considering the huge range of depths in the ocean? Challenger is something like 8 miles deep, whereas areas of the northern Indian ocean are barely a mile.

There is no mass of water that does not circulate. There are areas of faster or slower circulation, (mostly, but not entirely, to do with the topography of the ocean floor) but the oceans waters are constantly circulating.
thermodynamics
4.5 / 5 (8) Jun 03, 2014
the deep ocean abyss.

How deep is that?
I have been trying to find the median depth of the ocean, but all that I have found on-line is mean.
It varies a lot, such that the mean is usually given when you search for an overall number. Average depth is about 2.65 miles (4.3KM). This gives an overview: http://oceanservi...pth.html

I already know this.
What's most important is the median. Half the water is below this depth.
I you want to use the mean, then half the ocean is below 4 km.
What is the mass of water that does NOT circulate?


Rygg2: I did the unusual and searched Google for "median ocean depth." I know, who woulda thunk that would work. The 4th entry in my search is a PDF called "00observations.pdf" and it has a graphic with the mean at 3734 m and the median at 4093 m. That should give you something to work with. The paper is: OBSERVATIONS RELATED TO PLATE TECTONICS from UCSD.
ubavontuba
1.7 / 5 (6) Jun 04, 2014
...or maybe not. It depends on how civil you can be.


Provide proof that you deserve to be treated with civility.
I'm human.
Maggnus
4 / 5 (8) Jun 04, 2014
Provide proof that you deserve to be treated with civility.
I'm human.
Wow Uba, resorting to the fallacy of Special Pleading. Except, we have been down this road before.

What's the matter, has your handbook of denialist slogans run dry? Why don't you put up your cherry picked chart and restate your false claim that a measure of the surface temperatures means the heat budget of the planet is not skewed, or the cherry-picked chart of sea surface temperatures and claim that this somehow means the oceans are not heating. Surely you can still find an article about that one single glacier in Alaska that is growing while the thousands of others are shrinking, then claim that means glaciers are not melting.

You are treated with scorn and disdain because you have earned it. You wear your ignorance and denialism like a badge of honor. You treat scientists like enemies, then cry foul when they return the favour. You reap exactly what you have sown.

rockwolf1000
4.5 / 5 (8) Jun 04, 2014
...or maybe not. It depends on how civil you can be.


Provide proof that you deserve to be treated with civility.
I'm human.


And? You think that counts for something? You're in the business of spreading BS which directly impacts my quality of life and the prospects of my offspring to have a high quality of life. The planet we depend on is in peril from pollution and greed and human sprawl and you continually interject your contrarian opinions to support your world view. You continually suggest that adding CO2 or burning other fossil fuels is ok yet this is the very same atmosphere I breathe and you have no right to suggest it's ok to pollute it further. Moreover you incessantly make ridiculous suggestions such as:

"I can't help but think that top image, of an icebound earth, looks like an AGWite's dream come true."

If that's how your brain works it speaks volumes about your opinions.

If you really are partially retarded I do apologise however.
ubavontuba
1.5 / 5 (8) Jun 04, 2014
LOL, I can't help but think that top image, of an icebound earth, looks like an AGWite's dream come true.
And it WOULD BE a dream come true for you, ubybooby --and your very fondest, too!

But dreams are dreamt to be shatterd, ubybooby, as this is a perfect example of the NEGATIVE correlation between atmospheric CO2/GHG content and average global temperatures.

By the way --how's that Northern Hemisphere snow and ice increase looking these days?
Northern sea ice looks okay. A bit below average, but nothing to panic over. Of course the counter balance is the Antarctic is well above average.

http://nsidc.org/...icenews/

Have you recently visited the NSIDC?
Personally? No. But I view the website from time to time.

Or have they fallen out of favor with you, since the yearly, seasonal(aka, "weather") average and extent data can no longer be claimed by you as support for a downward surface temperature trend?
I haven't used them for surface temperatures, have I? When? Where?

I used them a few times for ice and snow data, but I generally prefer The Cryosphere Today.

Are the Colorado glaciers still growing in mass and extent?
I don't know. Did I make this claim? When?

I can't find much information either way. But glaciers have been retreating in North America for a long time (long before the supposed AGW), as we've relatively recently come out of the Little Ice Age.

But glaciers grow and glaciers shrink. It must be this way, or the world would be covered in ice.

ubavontuba
1.5 / 5 (8) Jun 04, 2014
Hahah I forgot about this one! He argued for DAYS that that one year where the mass loss was less than the yearly mass lost in each of the previous 10 years was a sign of temperatures turning around.The fact it was still losing mass and that it was the amount of mass it lost was what was less completely flew over his head! I still laugh at that one!
What are you talking about. I use temperatures to show that temperatures have turned around.

http://www.woodfo....3/trend

Don't forget though, Uba thinks we can grow food in deserts! The fact that we can irrigate some small areas of desert means, in his mind, that deserts are open for cultivation. Hope he's right for the sake of the SW US.
Ooh, Maggnus is still smarting over this one. I guess he's such a moron he can't admit he was wrong, even after viewing images like these:

Desert Agriculture

He probably still thinks there is no agriculture in Nevada.

I wonder, has Maggnus has never even seen a Prickly Pear? You know, the cactus fruit?

http://upload.wik...seup.jpg

Yes, Maggnus. People really eat them.

I wish he would move into the middle of one with a few seeds for a year. I'll even pitch in a 3 month supply of water. What, maybe you think they don't have internet access in the desert either?

ubavontuba
1.5 / 5 (8) Jun 04, 2014
Provide proof that you deserve to be treated with civility.
I'm human.
Wow Uba, resorting to the fallacy of Special Pleading. Except, we have been down this road before.

What's the matter, has your handbook of denialist slogans run dry? Why don't you put up your cherry picked chart and restate your false claim that a measure of the surface temperatures means the heat budget of the planet is not skewed, or the cherry-picked chart of sea surface temperatures and claim that this somehow means the oceans are not heating.
So you're saying you don't beieve in empirical data? Are you just living in an AGWite fantasy now, where temperatures don't matter?

You are treated with scorn and disdain because you have earned it. You wear your ignorance and denialism like a badge of honor. You treat scientists like enemies, then cry foul when they return the favour. You reap exactly what you have sown.
I only cry foul when I smell foul.

Some science is particularly good, and I have stated so - often. But the AGWite "science" is rife with lazy "scientists" only bothering to search for evidence to support their preconceptions.

It's so bad, the "mainstream science" has veered almost entirely away from the atmospheric temperatures which are at the very heart of the definition for Global Warming:

"global warming
n.
An increase in the average temperature of the earth's atmosphere, especially a sustained increase sufficient to cause climatic change."

...and opt instead to discuss unverifiable kinetic energy effects.

So please explain the theory behind this magical transformation from the CO2/Greenhouse Heat Trapping Theory to the CO2/Kinetic Energy Trapping Theory. What are the mechanisms? How does it work? Why isn't the CO2/Greenhouse Heat Trapping Theory working?

ubavontuba
1.5 / 5 (8) Jun 04, 2014
...or maybe not. It depends on how civil you can be.
Provide proof that you deserve to be treated with civility.
I'm human.
And? You think that counts for something? You're in the business of spreading BS which directly impacts my quality of life and the prospects of my offspring to have a high quality of life. The planet we depend on is in peril from pollution and greed and human sprawl and you continually interject your contrarian opinions to support your world view. You continually suggest that adding CO2 or burning other fossil fuels is ok yet this is the very same atmosphere I breathe and you have no right to suggest it's ok to pollute it further.
You exhale CO2, moron.

Moreover you incessantly make ridiculous suggestions such as:

"I can't help but think that top image, of an icebound earth, looks like an AGWite's dream come true."

If that's how your brain works it speaks volumes about your opinions.

If you really are partially retarded I do apologise however.
No, a ridiculous suggestion is that the globe is warming, when it isn't, or the ice melting is a bad thing, when cold has historically killed many times the people that warm temperatures have.

Why do the AGWites desire destruction?

runrig
4.1 / 5 (9) Jun 04, 2014
...or maybe not. It depends on how civil you can be.


Provide proof that you deserve to be treated with civility.
I'm human.
And? You think that counts for something? You're in the business of spreading BS which directly impacts my quality of life and the prospects of my offspring to have a high quality of life. The planet we depend on is in peril from pollution and greed and human sprawl and you continually interject your contrarian opinions to support your world view. You continually suggest that adding CO2 or burning other fossil fuels is ok yet this is the very same atmosphere I breathe and you have no right to suggest it's ok to pollute it further. Moreover you incessantly make ....

If you really are partially retarded I do apologise however..

Worth a 10 rock
rockwolf1000
4.5 / 5 (8) Jun 04, 2014
@ ubamoron

"You exhale CO2, moron."

Wow, aren't you smart?
But I don't exhale mercury, uranium, thorium, arsenic, and other heavy metals, which is what goes into the air when fossil fuels are burnt. You think I only care about AGW? How did you become so simple? We have had 350 consecutive months of above normal temperatures globally, the oceans are getting warmer and the glaciers and the ice caps continue to lose mass. Ergo the planet is getting warmer as a whole. Can you not add? Your continued suggestion the planet has been cooling for 17 y is directly refuted by the receding glaciers. When temperatures are cool glaciers grow. They are not growing. I have 20 year old maps that show access points to glaciers and ice fields and the toe of the glacier is nowhere near where the map shows. Climbing route descriptions that state Bergshrund sizes at 2-3' are actually a gaping 20-30' across and bottomless. Un-passable. You think this would be happening on a cooling planet? Beyond stupid!
Maggnus
4.1 / 5 (9) Jun 04, 2014
Northern sea ice looks okay. A bit below average, but nothing to panic over. Of course the counter balance is the Antarctic is well above average.
Wow, you really are stupid! Like , mind-numbingly, off the chart, stupid. The Arctic sea ice levels are trending BELOW the record setting pace of 2012. This, from YOUR OWN CITE!

Pigeon chess.

What are you talking about. I use temperatures to show that temperatures have turned around.
That you don't understand is of no surprise. That you continue to display how incredibly stupid you are is also of no surprise.

Caliban
4 / 5 (8) Jun 04, 2014
Hahah I forgot about this one! He argued for DAYS that that one year where the mass loss was less than the yearly mass lost in each of the previous 10 years was a sign of temperatures turning around.The fact it was still losing mass and that it was the amount of mass it lost was what was less completely flew over his head! I still laugh at that one!


What are you talking about. I use temperatures to show that temperatures have turned around.


And sure you do, ubybooby --and only the finest, cherry-picked ones, to be sure.

Of course, as you well know, maggnus was referring to your oft-repeated claims of only a couple of years ago that (especially) North American seasonal ice/snow cover extent was at record amounts --and therefore AGW was a sham.

But you weren't satisfied with that preposterous assertion, and felt compelled to go further, and claim that the glaciers of Glacier National Park were in fact Growing.

Therefore, you are a lying, prevaricating, moron troll.

Egleton
not rated yet Jun 08, 2014
If my powers of comprehension haven't failed completely I undertand the article to suggest that the oceans could not get rid of their CO2. Surely they would have been more acidic. And if so how did the Coccolithophores tolerate the acidic environment? The bottom of the web of life is more important than the top.
I am hopeful that this is evidence that the Coccolithophores can survive the acidification.
I am not all that partial to jellyfish soup.