From the National Science Foundation: Press Release 14-081
Ancient ocean currents may have changed pace and intensity of ice ages
Climate scientists have long tried to explain why ice-age cycles became longer and more intense some 900,000 years ago, switching from 41,000-year cycles to 100,000-year cycles.
Slowing of currents may have flipped switch
About 950,000 years ago, North Atlantic currents, Northern Hemisphere ice sheets underwent changes. |
June 26, 2014
Climate scientists have long tried to explain why ice-age cycles became longer and more intense some 900,000 years ago, switching from 41,000-year cycles to 100,000-year cycles.
In a paper published this week in the journal Science Express, researchers report that the deep ocean currents that move heat around the globe stalled or may have stopped at that time, possibly due to expanding ice cover in the Northern Hemisphere.
“The research is a breakthrough in understanding a major change in the rhythm of Earth’s climate, and shows that the ocean played a central role,” says Candace Major, program director in the National Science Foundation (NSF)’s Division of Ocean Sciences, which funded the research.
The slowing currents increased carbon dioxide (CO2) storage in the oceans, leaving less CO2 in the atmosphere. That kept temperatures cold and kicked the climate system into a new phase of colder, but less frequent, ice ages, the scientists believe.
“The oceans started storing more carbon dioxide for a longer period of time,” says Leopoldo Pena, the paper’s lead author and a paleoceanographer at Columbia University’s Lamont-Doherty Earth Observatory (LDEO). “Our evidence shows that the oceans played a major role in slowing the pace of the ice ages and making them more severe.”
The researchers reconstructed the past strength of Earth’s system of ocean currents by sampling deep-sea sediments off the coast of South Africa, where powerful currents originating in the North Atlantic Ocean pass on their way to Antarctica.
How vigorously those currents moved can be inferred by how much North Atlantic water made it that far, as measured by isotope ratios of the element neodymium bearing the signature of North Atlantic seawater.
Like tape recorders, the shells of ancient plankton incorporate these seawater signals through time, allowing scientists to approximate when currents grew stronger and when weaker.
Over the last 1.2 million years, the conveyor-like currents strengthened during warm periods and lessened during ice ages, as previously thought.
But at about 950,000 years ago, ocean circulation slowed significantly and stayed weak for 100,000 years.
During that period the planet skipped an interglacial–the warm interval between ice ages. When the system recovered, it entered a new phase of longer, 100,000-year ice age cycles.
After this turning point, deep ocean currents remained weak during ice ages, and ice ages themselves became colder.
“Our discovery of such a major breakdown in the ocean circulation system was a big surprise,” said paper co-author Steven Goldstein, a geochemist at LDEO. “It allowed the ice sheets to grow when they should have melted, triggering the first 100,000-year cycle.”
Ice ages come and go at predictable intervals based on the changing amount of sunlight that falls on the planet, due to variations in Earth’s orbit around the sun.
Orbital changes alone, however, are not enough to explain the sudden switch to longer ice age intervals.
According to one earlier hypothesis for the transition, advancing glaciers in North America stripped away soils in Canada, causing thicker, longer-lasting ice to build up on the remaining bedrock.
Building on that idea, the researchers believe that the advancing ice might have triggered the slowdown in deep ocean currents, leading the oceans to vent less carbon dioxide, which suppressed the interglacial that should have followed.
“The ice sheets must have reached a critical state that switched the ocean circulation system into a weaker mode,” said Goldstein.
Neodymium, a key component of cellphones, headphones, computers and wind turbines, also offers a good way of measuring the vigor of ancient ocean currents.
Goldstein and colleagues had used neodymium ratios in deep-sea sediment samples to show that ocean circulation slowed during past ice ages.
They used the same method to show that changes in climate preceded changes in ocean circulation.
A trace element in Earth’s crust, neodymium washes into the oceans through erosion from the continents, where natural radioactive decay leaves a signature unique to the land mass from which it originated.
When Goldstein and Lamont colleague Sidney Hemming pioneered this method in the late 1990s, they rarely worried about surrounding neodymium contaminating their samples.
The rise of consumer electronics has changed that.
“I used to say you could do sample processing for neodymium analysis in a parking lot,” said Goldstein. “Not anymore.”
-NSF-
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‘The slowing currents increased carbon dioxide (CO2) storage in the oceans, leaving less CO2 in the atmosphere.’
Which meant that the oceans became acidic and all the sea shells dissolved, or not as the case may be.
This quote gives me pause: “The ice sheets must have reached a critical state that switched the ocean circulation system into a weaker mode,” said Goldstein.
They make a lot of claims from a rather weakly related proxy — they can be pretty sure about neodymium ratios but there may be more reasons than “strength of ocean currents” to explain their rise and fall off the coast of South Africa. Assuming a proxy is the equivalent of just the “thing” your group is looking for is not necessarily sound science — sorta like tree rings are a thermometer.
What is this fixation with CO2???
All hat needs to be said is that slowing or stopping currents transporting warm equatorial water towards the poles to keep the ice caps at bay, allowed them to expand even further.
They always have to mention co2 in some way which takes away from the article
They had to throw CO2 into the paper to get it published I guess, eh? I doubt that CO2 had much to do with stopping or starting glaciation episodes, although their point about the thermohaline currents slowing down is a rather obvious one. Of course these would slow down during a glaciation period. Everything slowed down except the rush to the nearest trading post to get a thicker parka.
Just amazing how that tiny little gas up there in the sky controls nearly everything.
Then there is that stuff that horses do in paddocks after a big feed of oats….what’s it called again? I know…..horse$h*t
My hero a must see confirms everything Goddard has said
Prof Don Easterbrook
Especially the NOAA data tampering bit. He showed this in 2013.
In particular the “earlier adjusments”
They need the CO2 statement to get through peer review more quickly. If they left it out, a reviewer would probably suggest they add it in or tack modern temperature data on the end.
If glacial periods are so predictable due to orbital changes, when is the next one due?
And what became of the theory that only Earth core temp changes due to playing out of nuclear fuel were great enough to explain massive temp drops. And how does the Earth ever manage to get out of a glacial period, according to these guys? Pretty superficial article.
methinks that with all that CO2 being dissolved in the ocean, there would not have been much atmospheric CO2 to support photosynthesis. How was the plant life in the tropics during this CO2 starvation?
Slowing currents increased CO2 transfer???
@ur momisugly Col Mosby
“If glacial periods are so predictable due to orbital changes, when is the next one due?”
That is a good question. If the control of these periods is by the three Milankovitch cycles, at the current time, only one of these cycles is standing in the gap between this interglacial and the next glaciation period; and that one, obliquity, will be going into the bottom end of its 41,000 year cycle in about 850 years. Neither of us will be around to see it, but then, it is only theory we are talking about. It could come tomorrow, or, 5,000 years from now. Regardless, glaciation will come and will last for 85,000 to 90,000 years as it has done so for 10 times already in the last million years.
Mark Wagner
Plants in general don’t seem to do very well when CO2 is lowest…
http://www.climatedata.info/Impacts/Impacts/dust.html
If ,as suggested the climate cooled because all the CO2 was taken out of circulation, how the hell did it warm again with all the vegetation virtually dead? Surely the ice age must have been self pepetuating?
“The slowing currents increased carbon dioxide (CO2) storage in the oceans, leaving less CO2 in the atmosphere. That kept temperatures cold and kicked the climate system into a new phase of colder, but less frequent, ice ages, the scientists believe.”
Oh my, that had to get CO2 into it somewhere, even if their research had nothing to do with CO2. I don’t give a flying fox what scientists “believe”. What is relevant is what their research shows, not personal “beliefs”.
So what their research actually showed is that ocean currents are a determinant factor in climate change. On the contrary their research does NOT show that CO2 amplified that or played any role whatsoever.
Following my earlier comment i suppose subsequent warming could have been triggered by errupting volcanoes. Does this sound feasible?
The assumption that the surface is generally in equilibrium without man made ghg’s is a poor assumption.
(energy budget)
“The slowing currents increased carbon dioxide (CO2) storage in the oceans, leaving less CO2 in the atmosphere. That kept temperatures cold and kicked the climate system into a new phase of colder, but less frequent, ice ages, the scientists believe.”
What utter nonsense! What part of CO2 ALWAYS lags temperature in ice cores don’t they get? On top of that, ocean currents don’t determine the amount of CO2 in the oceans–the water/air temperatures do. On top of that, what possible physical CO2 process would make subsequent ice ages less frequent?
Now that continental drift is accepted (took a while for the ‘experts’ to change their consensus on that one), what effect did this have on ocean currents 1,000,000 years ago?
Was this factored into their analysis?
” Philip says:
June 30, 2014 at 11:46 am
What is this fixation with CO2???”
Ceterum censeo carbon dioxide esse delendum!
It is a bit surprising that CO2 which has explained so little of current temperatures is still used to explain just about everything in the past. When will they ever learn?
Are climate scientist deficient in imagination?
Even with their bow to CO2 they are still admitting that it was a natural process, which is, in itself, quite an amazing admission. Of course their cause and effect is still questionable relative to the more simple warm water conveyor north being disturbed.
Mark Twain may have been speaking about climate science when he said “One gets such wholesale returns of conjecture out of such a trifling investment of fact”
cn
Londo says:
June 30, 2014 at 1:54 pm
It is a bit surprising that CO2 which has explained so little of current temperatures is still used to explain just about everything in the past. When will they ever learn?
Are climate scientist deficient in imagination?
————————————–
I believe I once heard someone say: when all you’ve got is a hammer, everything starts to look like a nail.
cn