That ocean currents switch flipping thing again

earth seen from outer space showing the North Atlantic currentsFrom 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

earth seen from outer space showing the North Atlantic currents
About 950,000 years ago, North Atlantic currents, Northern Hemisphere ice sheets underwent changes.
Credit and Larger Version

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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53 thoughts on “That ocean currents switch flipping thing again

  1. ‘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.

  2. 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.

  3. 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.

  4. 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.

  5. 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

  6. 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”

  7. 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.

  8. 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.

  9. 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?

  10. @ 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.

  11. 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?

  12. “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.

  13. Following my earlier comment i suppose subsequent warming could have been triggered by errupting volcanoes. Does this sound feasible?

  14. The assumption that the surface is generally in equilibrium without man made ghg’s is a poor assumption.

  15. “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?

  16. 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?

  17. ” Philip says:
    June 30, 2014 at 11:46 am

    What is this fixation with CO2???”

    Ceterum censeo carbon dioxide esse delendum!

  18. 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?

  19. 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.

  20. 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

  21. 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

  22. Eliza
    Thanks for the link to the DOn Easterbrook presentation, as you say a must watch.

    Don Easterbrook
    Thank you for the presentation.

  23. I don’t see any CO2 data presented in the paper.

    But I have detailed CO2 numbers and temperature estimates which will make this issue much clearer (about how fuzzy it is that is).

    All CO2 estimates available from reliable methods (14 sources) and Global temperature estimates from three different sources (which are remarkably similar). Global temperature estimates from the Antarctic ice core composites, do18 isotopes global temperature estimate from Lisiecki Raymo 2009 from cores in the North Atlantic, and Zachos 2001 do18 isotopes global temperature estimate which come from cores all over the world’s oceans). Didn’t know they were so similar.

    First 1.8 million years ago to today. Pretty hard to see the transition to the 100,000 year ice age cycles and one wouldn’t blame a CO2 drawdown for anything.

    And then a better zoom-in on the supposed transition timeline of 900,000 years ago covering 1.3 Mya to 0.6 Mya. I don’t see it. Scientists working from pre-conceived ideas again.

  24. “Climate scientists have long tried to explain.” Explaining the past does much less harm than predicting the future. Three cheers to climate scientists!

  25. This is a good read on the mid pleistocene revolution (MPR) i.e. the switch from 41000 to 100000 year periodicity of interglacials:

    http://andy.seao2.info/pubs/manuscript_maslin_and_ridgwell.pdf

    It is polluted by CO2 but nonetheless interesting e.g. in background information about glacial-interglacial cycling.

    The important message is that in the long term glaciation is deepening. From interglacials at 41k year intervals, to 100 k year intervals, to – if the trend continues – a future of uninterrupted glaciation with no interglacials – for a few tens of millions of years.

    An interesting question from this is – is this period of a few million years with interglacials a transition that always happens as the major glaciations develop? For instance the Cryogenian, 650-800 million years ago, and the Saharan-Andean, 420-460 million years ago: when these were just starting, did they also have an initial transitional period during which interglacials occured? It would be interesting to find records from those times with enough time resolution, maybe hard that long ago.

  26. “they showed that changes in climate preceded the changes in ocean circulation”

    Well yes that’s because its the changes in the jet stream / trade winds/ weather patterns that is the cause of the change in the ocean current. lt was not the ice sheets slowing the current down, it was the changes in the weather patterns at the time which slowed down the gulf stream so allowing the ice sheets to expand.

  27. A breakthrough. Why does such vapid stuff get called a breakthrough? Nd isotopes are a different mix in the different ocean basins because of differences in source rock eroded. I get that.

    http://www.onafarawayday.com/Radiogenic/Ch4/Ch4-5.htm

    I also get the value of oxygen isotopes in temp. But with a 3 parts per trillion Nd concentration in sea water (it is selectively absorbed into manganese nodules in the sea floor taking it out of solution). Nd does co-precipitate with Ca in shells – they have that correct (I have had trouble in design of ore processing of rare-earth ores because of this propensity with Ca, the major element in the ore), but I would like to know what the concentration is in the shells, what the variation in the isotope mix. What mix is considered significant and indicative of their hypothesis.

    Another thing is that when you are in an ice age, chemical weathering and erosion is reduced down strongly and river flow is a trickle. Additions of elements into solution are therefore much reduced. Most of it may come from re-erosion of exposed sea bed sediments. These are all confounding factors to a geochemist’s simple picture. Three parts per trillion and variability is a big problem all by itself. The changing geochemical environment with the ice cover, lower sea level, induced drought, reduced influx of Nd from the land and likely other factors, in my view make picking out the signal a hapless task. Surely the reduced Arctic meltwater during much of the glacial period could be a factor and possibly interference with the flow around South Africa by expansion of Antarctica ice (currently only 25 degrees latitude apart). This definitely a ceteris paribus type of analysis doesn’t apply here.

  28. Wouldn’t the oceans currents slow down and perhaps shift from the sea level dropping? There would be pressure changes all through the ocean basins.

  29. phlogiston says:
    June 30, 2014 at 3:39 pm

    The previous glaciation was during the Mesozoic, at the Jurassic/Cretaceous boundary, but it was weak. The most recent glaciation comparable to the current Cenozoic one occurred on the southern supercontinent Gondwana in the Carboniferous & Permian Periods of the Paleozoic.

    http://jgs.lyellcollection.org/content/169/2/119.abstract

    Its onset occurred at the “earliest Asbian (~337.5 million years ago) and the mid-Brigantian (late Visean) (c. 331 Ma)” (dates not in the original). The Visean is in the Mississippian or Early Cretaceous. The glaciation lasted until at least the middle of the Permian Period, perhaps 80 million years.

    The Cenozoic glaciation started about 38 million years ago with Antarctic ice sheet formation following the opening of deep channels between that continent, South America & Australia. Northern hemisphere ice sheets were added after the formation of the Isthmus of Panama about three million years ago.

  30. Col Mosby says:
    June 30, 2014 at 12:02 pm

    If glacial periods are so predictable due to orbital changes, when is the next one due?

    The next one has already started if you examine curves of temperature proxies beginning about 10 KYA. The planet finishes exiting the Younger Dryas over the following 2 KY reaches a temperature maximum from which the temperature has trended downward to the present. More to the point though, the ice age periodicity is the only unequivocal periodicity in climate data. There are no undebateable periodicities at any shorter term until we get down to annual patterns. That doesn’t mean there are none, simply that no one has pulled any out the data that is really convincing outside the discoverer and associates.

  31. Rather than the neo concentrations being controlled by the changing of the currents, it could also be explained by changing rainfall on the continents, varying the run off into the oceans.

  32. Surely during ice-ages, increased yearly sea ice formation plus increased katabatic winds from vast northern continents of ice would increase yearly deep water formation? increasing total ocean overturning–even if we cant recognise the structure of that circulation at present! This would increase co2 release from the oceans.

  33. This does not make sense to me. If the ocean currents slow down or stall that means the colder, deep ocean water stays at the bottom of the oceans longer while the warmer water stays on the surface longer. This should allow the surface water to be warmed by the sun. Since the top of the ocean and the atmosphere are generally in equilibrium, I would think this should warm the climate and outgas more CO2 into the atmosphere. What am I missing?

  34. Another interesting hypothesis on the MPT.

    The fly in the climate change soup known as CO2 has the largest problem of all. Assume for a moment that the alarmists are right about CO2. Now find a source of CO2 that reliably erupts at 100,000 year intervals (eccentricity) and 41,000 years (obliquity), close to the glacial maximum large enough to drive us out of an ice age? There’s not a whole heck of a lot kicking around after maybe 70-80kyrs, including humans. Not volcanoes. And not the glacial maximum oceans. Remember CO2 dissolves much better in cold water.

    So, if the alarmists are somehow right about CO2 being the thermostat, then it is even worse than THEY think. The two 800lb gorillas in the climate change room with them is where on earth (literally) do you get enough CO2 to cause obliquity/eccentricity paced ~400-foot sea level changes, and what could we do about it assuming we knew what that was? The larger gorilla is when we live, at a half-precession old interglacial. OK alarmists, let me get this straight, you want to remove CO2 from the late Holocene atmosphere BECAUSE it might be a good enough “climate security blanket” capable of delaying glacial inception? Or do you even know what epoch you live in and how big a difference that should make in your deliberations?

    If alarmists are right about CO2 that means Ruddiman is also right in his Early Anthropogenic Hypothesis,

    “The possible explanation as to why we are still in an interglacial relates to the early anthropogenic hypothesis of Ruddiman (2003, 2005). According to that hypothesis, the anomalous increase of CO2 and CH4 concentrations in the atmosphere as observed in mid- to late Holocene ice-cores results from anthropogenic deforestation and rice irrigation, which started in the early Neolithic at 8000 and 5000 yr BP, respectively. Ruddiman proposes that these early human greenhouse gas emissions prevented the inception of an overdue glacial that otherwise would have already started.”

    http://folk.uib.no/abo007/share/papers/eemian_and_lgi/mueller_pross07.qsr.pdf

    It doesn’t take a lot of marbles to realize that advocating for removal of CO2 from the late Holocene atmosphere could tip us into that “overdue glacial”. So even if alarmists are right about CO2, you would have to be shy a few marbles to even fantasize about removing it! So even if you are right about CO2/GHGs, you are wrong about what to do about it precisely of because of when you want to do it, at the now 11,717 year old Holocene.

    Even a caveman would get this.

    I have to leave it to the oceanographers as to how much this study contributes to our understanding of climate change. There are a lot of hypotheses regarding the MPT and ocean currents. And there are a lot of them that look at a host of other variables. I’m not sure we have the whole picture yet,

    The authors have built a case for the MPT. And skipping an interglacial is bad ju-ju. But Fred Hoyle probably stated it best in an essay published on CCNet back in 1999:

    “This is why the past million years has been essentially a continuing ice-age, broken occasionally by short-lived interglacials. It is also why those who have engaged in lurid talk over an enhanced greenhouse effect raising the Earth’s temperature by a degree or two should be seen as both demented and dangerous. The problem for the present swollen human species is of a drift back into an ice-age, not away from an ice-age.”

  35. Further to the above.The increase in co2 release from the oceans due to increased ocean overturning is more than offset by a decrease in ocean temperature which causes a net effect of increasing the ocean sink of co2

  36. Ocean currents by themselves change climate, since the oceans are where most climate heat resides. There is no need to invoke the agency of CO2.

  37. “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.”

    Yeah temperature going up or down leads CO2 with aprox 6-800 years. That means there is some sort of time teleconnection at work? The CO2 increase in 6-800 years is the cause for “today’s” temperature increase?
    What is next?

  38. “Yeah temperature going up or down leads CO2 with aprox 6-800 years. ”

    Actually the lead is much larger at the beginning of ice ages. More like a couple of thousand years.

    Another thing: the shift from 41 Ka to 100 Ka ice-ages also meant that the ice ages became markedly colder. But it also meant that interglacials became markedly warmer. I wonder how that is explained by this new shiny theory?

  39. The Post is really just the PR release about proposed past ocean current changes.
    Without the detail it is hard to know how to rate this attempt as press releases are often very poor at representing a paper.

    John in Oz says:
    June 30, 2014 at 1:48 pm
    “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?”
    In the past there have been several references to changed ocean currents as a climate changer ( in particular the closing of the Panama isthmus).
    There are several locations (and times) where continents drifting caused changes in ocean currents were likely to have significantly changed how the oceans redistributed heat around the globe.
    One of the important parts of the present oceans where the current has a major effect is the part of the southern ocean current that spears up the Chile/Peru coast to mix into the tropics in the Nino 1.2 region.
    This may play a part in preventing/reducing the frequency and strength of El Nino events.
    Only 3 million years ago the gap between Antarctica and South America started to open (look up :
    Antarctica Keystone of Gondwana
    By L.A. Lawver, I.W.D. Dalziel and L.M. Gahagan
    copyright 1999, University of Texas Institute for Geophysics June 25, 1999)
    to see their view of how Gondwana broke up and the oceans opened around it.
    If you can find “5.3 million years of delta O18 measutement from Ocean sediments (LR04) and an overall fit to Milankowitz harmonics”, they blame the change in temperature progression at 3 milliom years to the formation of the Panama Isthmus. try:-

    Others have placed the formation of the Panama Isthmus more recent. The same plot suggests change in the temperature progression at approx 1.5 million years and 0.9 million years ago (the Post above).
    There are several places where the ocean currents have been redirected by drifting continents, and I would urge people to consider more than their own prefered one.
    It is likely that the sea floor spreading south of Svalbard, and closer to the north pole, as well as the opening of the Siberia to Alaska gap were important.
    Note the obvious outpouring of cold arctic water at present into the Bering Sea. https://nsidc.org/sites/nsidc.org/files/images//arctic_map.gif
    All of these happened at a slow pace giving changes on the 0.5 to several million years, so Jolan’s query is not related to the continents moving.
    Bill as usuall has very relevant links to show CO2 lags (i.e. while CO2 may help a trend to continue it is not the primary cause).
    Bill Illis says:
    June 30, 2014 at 3:33 pm

    The first Graph could have a change in style around 900 thousand yrs ago http://s23.postimg.org/j3wqc16vf/CO2_Temps_last_1_8_Mys.png
    but CO2 lags the temp change by 50 to 100 Kyr

    Jolan says:
    June 30, 2014 at 12:53 pm
    “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?”
    In fact CO2 change lags the cooling (and warming).
    Others have suggested it is dust (from reduced precipitation and eventually plant growth stopping at low CO2 levels) that triggers a rapid melt to an interglacial.
    The dust plot earlier from ej supports this.
    ej says:
    June 30, 2014 at 12:45 pm
    dust- http://www.climatedata.info/Impacts/Impacts/dust_files/BIGdust_-_epica.gif.gif

  40. You don’t have to look at what happened 900,000 years ago yo see the influence of ocean currents on climate. You just have to go to the beginning of the twentieth century when a change in North Atlantic current system started to carry warm Gulf Stream water into the Arctic Ocean. Before that there was nothing in the Arctic but two thousand years of slow, linear cooling, caused by secular changes in the earth’s orbit. There was no parallel increase of atmospheric carbon dioxide with this warming and that rules out the greenhouse effect as a cause. This is because the IR absorbency of a gas in the infrared is an intrinsic property of the gas and cannot be changed. The warming paused for thirty years in mid-century, then resumed, and is still going on. The pause in warming was actually a cooling and most likely was caused by a temporary return of the previous flow pattern of currents. It is quite impossible for greenhouse warming to switch from warming to cooling and back to warming again. As a result, the Arctic today is the only part of the world that is still warming, while global warming as a whole stopped 17 years ago. This makes global warming “scientists” wonder why global warming works in the Arctic but fails to work in the Antarctic that is cooling. The answer is very simple: these lazy trouts did not read my article on Arctic warming in 2011 [E&E 22(8):1069-1083] or they would know that Arctic warming has nothing to do with their imaginary greenhouse warming and is caused by the change of North Atlantic current system at the turn of the century. Without this transfer of Gulf Stream heat north, both poles would be cooling at the same rate as Antarctica does today.

  41. milodonharlani says:
    June 30, 2014 at 4:57 pm
    phlogiston says:
    June 30, 2014 at 3:39 pm

    The previous glaciation was during the Mesozoic, at the Jurassic/Cretaceous boundary, but it was weak. The most recent glaciation comparable to the current Cenozoic one occurred on the southern supercontinent Gondwana in the Carboniferous & Permian Periods of the Paleozoic.

    http://jgs.lyellcollection.org/content/169/2/119.abstract

    Its onset occurred at the “earliest Asbian (~337.5 million years ago) and the mid-Brigantian (late Visean) (c. 331 Ma)” (dates not in the original). The Visean is in the Mississippian or Early Cretaceous. The glaciation lasted until at least the middle of the Permian Period, perhaps 80 million years.

    The Cenozoic glaciation started about 38 million years ago with Antarctic ice sheet formation following the opening of deep channels between that continent, South America & Australia. Northern hemisphere ice sheets were added after the formation of the Isthmus of Panama about three million years ago.

    Thanks for filling in my incomlete information about the major previous glaciations.

    What I was wondering was whether these glaciations also featured, at their initial onset, a period with periodic interglacials such as we are getting now. Would there be any proxy data with the resolution to see this?

  42. Arno Arrak on July 1, 2014 at 9:33 am

    You don’t have to look at what happened 900,000 years ago yo see the influence of ocean currents on climate. You just have to go to the beginning of the twentieth century when a change in North Atlantic current system started to carry warm Gulf Stream water into the Arctic Ocean.

    Do you think that a Gulf stream flowing into the Arctic would cause increased loss of heat from the oceans, with the northward carried heat being eventually lost to space?

  43. 1) I could swear I had heard that AGW was supposed to slow the Thermohaline circulation, bringing ice-thermageddon to Europe. That premise was the background of one of the AGW movies, the day after tomorrow, I believe. Now we learn that slowing ocean currents causes them to absorb more CO2. This would seem to be a dampening feedback. Who knew?

    2) A shout-out to John in Oz above.
    I was a bit disconcerted to see your name there, as I have used John_in_Oz as my internet nom de plume for the past ten years. It was assigned to me by the editor of an e-zine I wrote for, based on my (unused) first name and my country of origin.
    After Anthony made the case about not hiding behind identities, I’ve been using my normal name here. Of course, a day after he made that case, he told us his business had been targeted by the CAGW faithful, and more recently he mentioned his family coming under fire, so I might have been too easily persuaded. I continue to use it in other forums; not to hide my identity, but because that’s who I’m known as. I’ll continue to use the underscores, and in any case where there’s confusion over our identities, I’ll refer to myself as the good-looking one :)
    Cheers

  44. That kept temperatures cold and kicked the climate system into a new phase of colder, but less frequent, ice ages, the scientists believe.

    So how does a higher percentage of time spent in ice age scenarios, translate into “less frequent ice ages”?

    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?

    A lot of the analysis I’ve seen, states that the start of the ice ages was highly dependent upon the change of ocean currents due to the separation of the Atlantic from the Pacific due to the collision of Panama with South America, three million years ago.

    First we will freeze, then a few Billion years later, we will fry.

    So who is “we”? Modern humans have been around for a few thousand years. Supposing we don’t change the equation by producing some form of genetically modified or artificial life that completely alters the biosphere, the ten-million-year ice age postulated by Maslin & Ridgewell will be accompanied by the remainder of the CO2 in the atmosphere being scrubbed out by the Himalayas, our small blip notwithstanding.

    In that case the earth will be a cold, lifeless place, and then later a hot, lifeless place, and there will be no “we” to experience it.

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