From Harvard University Science: Scientists find signs of ‘snowball Earth’
Research suggests global glaciation 716.5 million years ago
Steve Bradt
Harvard Staff Writer
Geologists have found evidence that sea ice extended to the equator 716.5 million years ago, bringing new precision to a “snowball Earth” event long suspected of occurring around that time.
Led by scientists at Harvard, the team reports on its work in the latest edition of the journal Science . The new findings — based on an analysis of ancient tropical rocks in remote northwestern Canada — bolster the theory that the planet has, at times in the past, been covered with ice at all latitudes.
“This is the first time that the Sturtian glaciation [the name for that ice age] has been shown to have occurred at tropical latitudes, providing direct evidence that this particular glaciation was a ‘snowball Earth’ event,” said lead author Francis A. Macdonald, an assistant professor in Harvard’s Department of Earth and Planetary Sciences. “Our data also suggests that the Sturtian glaciation lasted a minimum of 5 million years.”
The survival of eukaryotic life — organisms composed of one or more cells, each with a nucleus enclosed by a membrane — throughout this period indicates that sunlight and surface water remained available somewhere on the surface of Earth. The earliest animals arose at roughly the same time, following a major proliferation of eukaryotes.
Even on a snowball Earth, Macdonald said, there would be temperature gradients, and it is likely that ice would be dynamic: flowing, thinning, and forming local patches of open water, providing refuge for life.
“The fossil record suggests that all of the major eukaryotic groups, with the possible exception of animals, existed before the Sturtian glaciation,” Macdonald said. “The questions that arise from this are: If a snowball Earth existed, how did these eukaryotes survive? Moreover, did the Sturtian snowball Earth stimulate evolution and the origin of animals?”
“From an evolutionary perspective,” he added, “it’s not always a bad thing for life on Earth to face severe stress.”
The rocks that Macdonald and his colleagues analyzed in Canada’s Yukon Territory showed glacial deposits and other signs of glaciation, such as striated clasts, ice-rafted debris, and deformation of soft sediments. The scientists were able to determine, based on the magnetism and composition of these rocks, that 716.5 million years ago they were located at sea level in the tropics, at about 10 degrees latitude.
“Because of the high albedo [light reflection] of ice, climate modeling has long predicted that if sea ice were ever to develop within 30 degrees latitude of the equator, the whole ocean would rapidly freeze over,” Macdonald said. “So our result implies quite strongly that ice would have been found at all latitudes during the Sturtian glaciation.”
Scientists don’t know exactly what caused this glaciation or what ended it, but Macdonald says its age of 716.5 million years closely matches the age of a large igneous province stretching more than 930 miles from Alaska to Ellesmere Island in far northeastern Canada. This coincidence could mean the glaciation was either precipitated or terminated by volcanic activity.
Macdonald’s co-authors on the Science paper are research assistant Phoebe A. Cohen; David T. Johnston, assistant professor of earth and planetary sciences; and Daniel P. Schrag, Sturgis Hooper Professor of Geology and Professor of Environmental Science and Engineering, all of Harvard. Other co-authors are Mark D. Schmitz and James L. Crowley of Boise State University; Charles F. Roots of the Geological Survey of Canada; David S. Jones of Washington University in St. Louis; Adam C. Maloof of Princeton University; and Justin V. Strauss.
The work was supported by the Polar Continental Shelf Project and the National Science Foundation’s Geobiology and Environmental Geochemistry Program.
Yup, Earth’s mercurial climate can certainly be pushed and pulled into some extreme states. People should feel quite lucky that the very stable Holocene era of the last 12,000 years has allowed the development of agriculture and civilization.
Hopefully nothing comes along to knock the climate system into a different, civilization ending state sooner than necessary – a global version of previous regional climate shifts that ended great civilizations.
With sea ice lapping up on beaches in the tropics, think how convenient it must’ve been to make Sturtian-era margaritas! No wonder the period led to animal life.
I’ve modified and reposted an OT comment from another thread that is on topic here.
I’ve Googled the theory, and note that while it has been debunked by at least one scientific study, and is not widely accepted, Connolley will not permit the Wikipedia article to be modified to reflect this.
The magical CO2 which is supposed to have ‘greenhoused’ the earth back to conditions more like what we experience now is supposed to have been generated by volcanoes. It occurs to me that CO2 concentrations argued to be necessary to have pulled the earth out of this condition at 130,000 ppm puts the warmists in rather a self-contradictory position: while CO2 is hypothesized to have been the forcing agent that brought the ’snowball’ condition to an end, the posited concentrations did not succeed in making the earth come to a boil – they merely allowed the ice to melt sufficiently to allow the Cambrian explosion!
Presumably the subsequent reduction of CO2 concentrations to modern concentrations was facilitated by autotrophs (i.e. photosynthesizing life forms). Life survived in far more extreme conditions and even at the worst levels of human activity, we are not projected to put anything near those levels of CO2 in the atmosphere. Just food for thought.
vigilantfish (19:47:10)
Interesting link, thanks, also…Those ‘dropstones’ are quite distinctive.
Evidence of this has been around since Budyko crafted his famous model back in ’79. We’ve had strong evidence via banded iron formations, paleomagnetic characteristics of rock, and glacial sediments from many locations, for quite some time.
From everything we know, it’s hard to explain exactly how Earth glaciated to the mid-latitudes (roughly the critical point, at which, the ice would enter an albedo feedback and march on to the tropics). The Milkanovitch cycles are nowhere near strong enough. On the other hand, escaping one is more imaginable: volcanic emissions mildly warm the planet over a long period of time, when sinks like plants would be scarce, and this releases some permafrost emissions and methane-clathrates, etc. You need quite a strong forcing to push that ice back to its critical point, though, because it will tend to want to keep returning to the equator.
Food for thought: of the models I’ve studied, they all allow a totally ice-free, partially ice-covered, and completely glaciated Earth to exist under our current solar constant. Given, it does not include things like the biosphere or the aforementioned volcanoes, but the high-albedo of a completely glaciated globe is enough to create a ‘stable’ climate, as is one with ice up to the mid-latitudes.
Am I correct in assuming that the illustration was not part of the PR, but added here. From the comments about CO2, people seem to be confusing the language in the artwork with the statement from Harvard which doesn’t really feature much discussion of CO2.
I know nothing about Geology and must just be confused, but how did the rocks from within 10 degrees latitude of the equator make it to a remote part of Northwestern Canada? Is the magnetism of the rocks enough to know for certain that they are from the tropics?
Why not find rock in the tropics that show the characterstics of glaciation? if there were glaciers in the tropics then why can’t we see evidence in the tropics rather than in the Yukon in Canada?
astonerii (19:16:44) :
Wow, isn’t it special? Every change in temperature has to be caused by CO2, as if there could not possibly have been some other reason.
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This little blurb on the paper already mentions the positions of the continents having an affect on climate, the albedo of growing sea ice compared to open ocean having an affect on climate, and I’d be surprised if the *actual paper* didn’t mention that the Sun was about 7% fainter (total solar irradiance) back then .
These are three rather large climate factors, none of which is CO2.
Climate scientists are well aware that CO2 is just one of many factors affecting Earth’s climate.
There either had to be land near the poles in order to kick this off or it had to be EXTREMELY cold.
Image the Southern Ocean without Antarctica in it. Sea water on the surface would cool until it sinks. This would pull in more warm water. So you would probably have various gyres where water sinks and they would probably merge at some point to create a colossal whirlpool at the pole. In other words, the ocean would probably do something akin to what the atmosphere of Saturn apparently does. You would need to cool nearly the entire ocean because it would be circulating like mad. The colder it got, the more warm water would get pulled in. The bottom of the ocean would be a general Northerly flow of cold water and the surface would be a generally southerly flow of warm. This would act to pull a lot of heat away from the tropics. I would expect the result to be less extreme temperature difference between the pole and the tropics than we see today with tropical heat relatively quickly transported to the Southern pole where it would radiate away, the water would sink and return Northward.
In the current Arctic situation, you have a nearly landlocked and relatively shallow ocean. Again, if the North pole had no land nearby, you would have the same mechanism operating there.
In the situation presented in the article, we might see ice forming on the continental land masses before actual sea ice! Heat is being rapidly transported away from the tropics to the poles which allows more ice to form on mountains in the tropics. As this ice begins to form, the albedo of the planet rises and the sea level begins to fall. Without land to hold sea ice in place or at least keep it corralled in a general location of the pole, it would drift away in summer to warmer water and melt each year. Without land at the pole, I would think it would be extremely difficult to get ice to form at the poles and stay there.
It seems more likely to me that ice began to form on the temperate mountains and began to spread as temperatures dropped. My guess is that the actually freezing of the ocean would have happened extremely quickly as nearly the entire body of water was cooled to near the freezing point. As sea levels dropped, more land becomes exposed. So the “shorelines” move both North and South closer to the poles. At some point during the winter, ice begins to form along the coastlines. So imagine it is Northern Hemisphere winter. Suddenly the ocean freezes from the Northern coastlines all the way to the pole in an extremely short period of time (couple of weeks). Albedo rapidly increases.
But I think the point here is that it might have froze from temperate region to pole and not from pole to temperate region if there was no land at either pole and a lot of land distributed around the planet in the tropics. If the oceans were colder than today, it is quite possible for ice to have formed along shorelines in winter as far South as 35N. It can form nearly that far South in winter today. I have seen ice at Lewes, Delaware which is at about 39N. It could then have very quickly covered the entire hemisphere in a matter of several days but it would have frozen from the “edges” toward the “center”, if you will, the same way a lake generally freezes.
Getting an ocean with no land near the pole to freeze from pole toward the tropics and getting that ice to stay there through the summer is probably not possible.
What makes them so sure the rocks weren’t on the top of a mountain or a tibeten style plateau?
……………….JFD (19:42:45) :
Anthony, I am a regular visitor, but primarily a lurker. I appreciate what you do very much. I think that you have done an excellent job of staying on top of the vast amount of rapid fire information since Climategate broke wide open. It has taken plenty of effort to do what you have done. Please be proud of yourself.
I believe that basic geology is the real key to understanding climate and has been left out of much, if not essentially all, of the climatologists studies. You do a good job of bringing a wide mix of science to your readers.
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JFD: A geologist (so he said) posted a blog entry somewhere on WUWT and said ‘I don’t know any geologists that believe in AGW’. One problem is that Geologists have been left out. THe other problem: Do you know any biologists who don’t believe in AGW? I started with the mutating/disappearing frog they’ll be the last to acknowledge AGW ain’t so because they ‘know’ it is. All these guys getting together for a media blitz are Biologists. Johnnny
Sheffield BM(Smallz79) (19:36:10) : “What really happen [sic] was a world wide flood, in which water came down from the sky and bursted [sic] out of the surface of the Earth all at once. This caused a simultanious [sic] and (comparered [sic] to millions of years) instantaneous movement of all land masses to were [sic] they are presently. This is all completely verifiable, you just have ask the right scientists. Which by the way the Earth is still holding all that water somewhere.”
And exactly who would those “right scientists” be? Give us their names, please.
One hypothesised trigger for Snowball Earth, which I assume the authors have noted, and which others have indeed noted, is the continental land mass configuration at the time possibly inhibited poleward-moving oceanic circulations transporting equatorial and near-equatorial ocean waters towards the poles.
Contemporary examples of oceanic circulations moving “oceanic heat” to the poleward regions are of course the Kuroshio, East Australian, Gulf Stream, Brazil, and the Agulhas circulations. And note the contemporary continental configurations – with major N-S oriented continental land mass margins adjacent to large open oceans, which facilitate such circulations. Contrast such a configuration with the inferred continental land mass configurations in the diagram presented by the authors.
So we should perhaps note continental configurations and their role in constraining or promoting heat transfer from the equatorial oceanic regions to the polar oceanic regions as a possible factor in initiation and termination of snowball earth scenarios.
These hypotheses are of course not new or original by any means…
Beware the brown bear (which is now white). as AGW forcings are now going to show up in…………………..climatic induced evolution adaptions (I hope Gore doesn’t read over at WUWT as maybe he hasn’t thought of it!)
Gary: plate tectonics and continental drift.
Regarding the scenario described in the illustration, wouldn’t it be more likely that the “tipping point” driving the planet to total ice coverage would be when the ice advanced enough to dramatically reduce the amount of H2O, the real greenhouse gas, in the atmosphere. And if volcanism ended it, wouldn’t it likely have been through the slow but always positive addition from sea floor geothermal activity building to another tipping point because the ice coverage suppressed the normal heat mixing mechanisms of the oceans. If after 5 million years that heat build up broke through the stratification and attacked the glaciated surface the resulting increase in atmospheric H2O and the oceans dumping heat to return to a more balanced state would account for the developed hothouse Earth and the eventual return to a more equilibrated state, without CO2 doing any more that its usual tag along function.
What a bunch of CO2 as thermostat brainwashing nonsense! As the article says they don’t know what caused the ice age Or why it ended. Those poor climate scientists with their carbon fixated minds. A shift in the earth’s axis easily explains radical changes in climate. Say, maybe thats why the geographical and magnetic poles don’t occupy the same location. Snowball earth, don’t believe it. Fauna sensitive to temperature have survived (i.e. tropical frogs). Honestly, people really do get paid for this stuff?
The Snowball Earth formation:
How about a really big asteroid hitting Venus at a glancing blow, making a huge cloud that migrates with the Solar Wind blocking a lot of the Sun from heating Earth?
It’s rotation is backwards with respect to the rest of the Solar System, except for Pluto.
“Because of the high albedo…of ice, climate modeling has long predicted that if sea ice were ever to develop within 30 degrees latitude of the equator, the whole ocean would rapidly freeze over,”
What ocean? The oceans are only 200 million years old at the most. See here
Reply: You appear to be confusing the age of the current rock on the sea floor with the age of the oceans. These are not the same thing. ~ ctm
“as if the well known “greenhouse” effect “shuts off” at certain levels of atmospheric composition, thus rendering significant additions to those levels, largely moot.”
That pretty much sums up my position on the topic. Once the level of saturation is reached, no further warming can occur from adding more. Once every last bit of infrared radiation has been absorbed, no possible increase in temperature can occur.
“Anu (20:48:51) : ”
My statement was based on the image, and I am seeing some people question whether that image was part of the study. So, if it was not part of the study, then my remarks are moot and pointless.
“Holy ice skating on the Amazon River, Batman!”
“That’s right, Robin. Just keep exhaling and by Tuesday we’ll be roller skating all the way back to Gotham City.”
Anon (20:34:35) :
“Is there really a desire to figure out what is going on, and what the actual risk levels are, to taking carbon that was sequestered over tens of millions of years and releasing it in what is essentially an almost instantaneous geological time period? ”
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I’m sorry, but, without releasing carbon, you could not even be asking such silly questions.
Tim McHenry (20:11:13) :
Studies like this, though speculative, base their findings on well documented field observations that can be readily checked and potentially refuted. Modern climate science ain’t quite so accommodating.
And anyway, as a geo-nerd, I think Snowball Earth is just plain cool!
Thank God. Now I can sleep tonight.