From the University of Texas at Austin
Scientists cast doubt on theory of what triggered Antarctic glaciation
A team of U.S. and U.K. scientists has found geologic evidence that casts doubt on one of the conventional explanations for how Antarctica’s ice sheet began forming. Ian Dalziel, research professor at The University of Texas at Austin’s Institute for Geophysics and professor in the Jackson School of Geosciences, and his colleagues report the findings today in an online edition of the journal Geology.
The Antarctic Circumpolar Current (ACC), an ocean current flowing clockwise around the entire continent, insulates Antarctica from warmer ocean water to the north, helping maintain the ice sheet. For several decades, scientists have surmised that the onset of a complete ACC played a critical role in the initial glaciation of the continent about 34 million years ago.
Now, rock samples from the central Scotia Sea near Antarctica reveal the remnants of a now-submerged volcanic arc that formed sometime before 28 million years ago and might have blocked the formation of the ACC until less than 12 million years ago. Hence, the onset of the ACC may not be related to the initial glaciation of Antarctica, but rather to the subsequent well-documented descent of the planet into a much colder “icehouse” glacial state.
“If you had sailed into the Scotia Sea 25 million years ago, you would have seen a scattering of volcanoes rising above the water,” says Dalziel. “They would have looked similar to the modern volcanic arc to the east, the South Sandwich Islands.”
Using multibeam sonar to map seafloor bathymetry, which is analogous to mapping the topography of the land surface, the team identified seafloor rises in the central Scotia Sea. They dredged the seafloor at various points on the rises and discovered volcanic rocks and sediments created from the weathering of volcanic rocks. These samples are distinct from normal ocean floor lavas and geochemically identical to the presently active South Sandwich Islands volcanic arc to the east of the Scotia Sea that today forms a barrier to the ACC, diverting it northward.
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  IMAGE: This is a reconstruction of the Scotia Sea area 25 million years ago, showing volcanoes of the ancestral South Sandwich arc (ASSA). They are now submerged, but were active at…Click here for more information. |
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Using a technique known as argon isotopic dating, the researchers found that the samples range in age from about 28 million years to about 12 million years. The team interpreted these results as evidence that an ancient volcanic arc, referred to as the ancestral South Sandwich arc (ASSA), was active in the region during that time and probably much earlier. Because the samples were taken from the current seafloor surface and volcanic material accumulates from the bottom up, the researchers infer that much older volcanic rock lies beneath.
Combined with models of how the seafloor sinks vertically with the passage of time, the team posits that the ASSA originally rose above sea level and would have blocked deep ocean currents such as the ACC.
Two other lines of evidence support the notion that the ACC didn’t begin until less than 12 million years ago. First, the northern Antarctic Peninsula and southern Patagonia didn’t become glaciated until less than approximately 12 million years ago. And second, certain species of microscopic creatures called dinoflagellates that thrive in cold polar water began appearing in sediments off southwestern Africa around 11.1 million years ago, suggesting colder water began reaching that part of the Atlantic Ocean.
The research team also includes Larry Lawver and Marcy Davis at The University of Texas at Austin’s Institute for Geophysics; Julian Pearce at Cardiff University (U.K.); P.F. Barker at the University of Birmingham (U.K.) (deceased); Alan Hastie at Cardiff University and the University of Edinburgh (U.K.); Dan Barfod at the Natural Environment Research Council’s Argon Research Facility (U.K.); and Hans-Werner Schenke at the Alfred Wegener Institute (Germany).
Support was provided by the U.S. National Science Foundation’s Office of Polar Programs, the U.K. Natural Environment Research Council, the Alfred Wegener Institute (Germany) and the British Antarctic Survey.
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As far as I can tell, the ACC goes between the Falklands and South Georgia (http://en.wikipedia.org/wiki/File:Antarctic_Circumpolar_Current.jpg) and the barrier that this paper is talking about does not appear to block that line. I’m not saying the paper is wrong, but I would appreciate clarification.
Actually, until the ASSA finally opened, the current was really the Antarctic Mostly Circumpolar Current. /Humour alert
It actually would make some sense. The southern Atlantic currents cycle counterclockwise at present. You can visualize a major circulation system coming down the coast of eastern South America, feeding eastward along the coast of Antarctica into the Indian Ocean, passing between Australia and Antarctica along the coast of Antarctica and then up the western coast of South America, before circulating westward again. It would require a counter current between South Africa and Antarctica. The break between South America and the Antarctic Penninsula would be trivial and probably would not affect the atmospheric circulation, which probably at least as important.
How are the dating of the Antarctic fossils coordinated with the continent being at different latitudes while going through various aeons of climate changes? i.e. what is taken as the determining factor when all three are varying slowly over time?
Antarctica has been in approximately the same location near the South Pole since at least the late Mesozoic, and the paleontology tells us that it was temperate until the late Oligocene,with plant-eating dinosaurs and similar temperate fauna. It did not freeze up, contrary to popular opinion, until the establishment of the Circumpolar Current.
Similarly, the Arctic did not freeze until the rise of the Isthmus of Panama sometime in the Miocene.
People really need to get their heads around the fact that ocean currents do more to modify the climate than any amount of CO2. .
There is two known Antarctic active volcanoes and Mt Erebus belongs to Australia. Most were active during the Holocene era some still grumbling. There is one under the sea too. Many are still considered dormant but not extinct having erupted within the last 15,000 years.. Did you not remember in primary school to rote the number of continents? Now when I was in school there were five.
“Asia, Africa, Americas, Europe and Antarctica. The Arctic is not a continent.” Now there are seven – Asia, Africa, South and North America, Europe, Australia and Antarctica. The Arctic is still not a continent. Most geologists note, that the Antarctic only melts sea ice, not land ice. And if there is a big ice shelf dislodged as it did some years ago, not from global warming, but a collision between glaciers, warning are put out to anyone sailing near by. But no danger was noticed.
George if I remember rightly, 250 million years ago, the whole planet was ice, and it was volcanic eruptions that suddenly changed the climate, and produced plants. Just a bit of trivia. Some scientists believe, that Earth is naturally an ice planet, and shifts between glacial and warmer periods all the time. The warmer periods generally only last for 10 – 15,000 years, depending on which hemisphere is affected. We’re over due for another I fear. It will be the ice and not fire that kills us, and the Southern Hemisphere will be the place to live.
steveta_uk says:
July 12, 2013 at 6:47 am
phlogiston, I thought that it also was clear evidence that we don’t own the Falklands, so I’d keep quiet about it.
Britannia rules the Waves, therefore Britannia waves the Rules!
Margaret Thatcher
Mac the Knife. The Falkland Isles is under the protection of the British, but self governing under a British Governor. Children are educated under the British school system and sit their A levels in Britain. Bermuda is still a crown colony too, although self governing. I don’t know what is the problem with it, other than the Argentinians wanting it, as it is 90% farm land, a rock or two rocks in the sea, freezing cold most times and subject to storms etc. But it was made a naval base years ago by the Brits. Probably its strategic position is what is worrying the Argentinians.
Thanks for that excellent post and collection of important links.
It really is about time we shift the focus back to the 800 pound gorilla in the room and leave the CO2 mouse squeaking in the corner where it belongs.
How the hell did the climate clowns manage to divert an entire generation away from real Science to instead follow these madman down infinite pseudoscience rabbit holes? Wegener comes along with a critical piece of the geological and climatic puzzle, yet a religious cult full of intellectual underachievers sidetracks it in favor of worshiping their patron saint Arrhenius.
All it takes I guess is a bunch of celebrities to hypnotize the sheeple and poison their minds. Ever since Sagan and Ehrlich and later, Hansen and Mann started spending more time in front of cameras than in the laboratory they became addicted to fame and fortune at the expense of logic and common sense.
I blame the general public though. If they weren’t so enamored of the cult of personality these idjits might be employed writing grade “B” Science Fiction for the SyFy channel where they belong.
The general public on many continents does not study science or understand it, just like many other issues of the day. When a college drop out like Al Gore, flying in his private jets from his many mansions to spread the faith about Goreballwarming and the need to reduce emissions (other than his hot air) gets to be the high priest of global warming, you need not go further.
The media tilts mostly left, and the Thatcher attack on CO2 as a reason to close the worn-out pits gets forgotten as the political nonsense it was then, and is still even if adopted by the true believers like Gore and Obama and most politicians in the West, from Europe to Australia. I guess they had to do something to replace eugenics.
Yes, and if the labor party in UK and also Australia had their way, they would be teaching our kids their slant on climate change a la science. I remember P.E.T.A delivering leaflets to school kids, stating “Your parents are murderers”. Trying to politically manipulate children or young adults is indocrination like the Nazi’s and Chinese. It’s almost like the education programs that Palin was encouraging. Remove the books and teach only creationism in the schools as science. Almost like those court cases over teaching Darwinism and the Holy Bible in the early 20th century. But some fundementalist Christians, even the Witnesses now recognise, six days when multiplied by millions of years is correct as the processes actually fit in with scientific fact. Not the ‘we walked with Dinosaurs’ theory promoted by the likes of Sarah Palin. (If we had we wouldn’t have evolved).
Going by this, admittedly coarse graph, the sea levels 28-12Ma may have been low enough for the proposed volcanic barrier to work.
This is all bunk – even the “new and improved” evidence and its interpetation. We are scientifcally maybe 1-2% knowledgeable about all these processes. We aren’t even near the middle of the initial discovery phase. All the conclusions drawn in our lifetimes about all this is premature ejaculations of the mental kind. They are jumping to conclusions, and if they continue to INSIST on drawing conclusions, their conclusions will continue to be sophomoric bleatings.
For those who think of science as a collection of facts, I’ve got a clue for you:
Science is a collection of interpretations of the evidence, not the evidence itself. There is a BIG difference. Evidence itself can never be wrong; it is itself and nothing more. The “science” comes in when someone tries to shoe-horn that evidence into their overall concept(s) of what the Big Picture is.
So far, all Big Pictures have proven to be ultimately wrong. The current Big Pictures will go the way of the T-Rex, too, in their time. At this toddler stage of science we can barely walk, much less actually understand the interplays and workings of the planet and universe. We are barely into the “hold onto furniture as we creep around the room” stage – and yet our thinker fellow toddlers are yelling cross the room, “HEY! I’ve found out the secrets of quantum physics!” – as they fall back on their diapered butts and explore their navels for the first time…
This kind of public “Eureka! We’ve Done it!” science is pretty nauseating. They don’t know JACK about what happened 12 or 25 Mya. They have like 6 pieces of evidence, around which they’ve constructed a mountain of supposition and extrapolation. Literally, they know as much about this as I do about opera. Almost certainly less. PROBABLY less, if we allow for negative values. Knowing something that is WRONG – I think that counts as negative knowledge, because you have to unlearn it just to get back up to zero.
Why can’t they just say, “We’ve found out some new facts.” and let it go at that? Nope, they have to spin an entire world view out of a twig.
@bushbunny:
…I don’t know what is the problem with it, other than the Argentinians wanting it, as it is 90% farm land, a rock or two rocks in the sea, freezing cold most times and subject to storms etc. But it was made a naval base years ago by the Brits. Probably its strategic position is what is worrying the Argentinians….
The Argentines originally seem to have made a claim for it in the 1830s for strategic reasons – they had gained independence from Spain and did not want a possible foreign staging post for invasion so close to their borders. Britain retained it because it was strategically valuable to their navy – it used to be an important Royal Navy coaling station back in the late 1800s/early 1900s. Occasionally, Argentina offered to withdraw the claim in return for debt forgiveness, but this was a low-key issue.
It would probably have ceased being an issue if it had not been used as a rallying cry by Peron in the 1940s/50s to divert attention from internal problems, and has been so used ever since. At the moment Argentina primarily wants it as a matter of national honour (though if oil is discovered that would be an added reason). And the strategic one still exists – Chile has been known to be less than friendly in that area…
The British government establishment (the Foreign Office) famously did NOT want it after its strategic importance diminished during the 1960s, and had been trying (against the wishes of the inhabitants) to transfer it to Argentina. The inhabitants managed to block this during the 1970s, but the diplomatic attitude conveyed to Argentina during this period was a major factor in the decision to invade – it was assumed that the UK would not reverse a ‘fait accompli’ which produced a result they desired…
Bushbunny, your memory is better than mine, since it seems to go back to the Permian or before. In fact, most of the time since the Precambrian the Earth has been much warmer than it is now. About 10 degrees Celsius warmer than the present average of a little more than 15 degrees Celsius. Indeed there was an ice age coincident with the rifting apart of Pangea at the end of the Permian, but the Earth stayed warm, quite warm in the Paleocene, until the Oligocene. All that time, the Mesozoic and early Cenozoic, Antarctica was an ice-free temperate continent located near where it is now.
That last “warm period” was 140 million years long – warm conditions are apparently the normal state of the Earth, and as we climb out of the most recent, and brief, cold plunge of the Pleistocene, we are just going back to normal.
I suggest you check C. Scotese’ temperature curves and maps at his useful Paleomap Project, available on the web.
Bill Illis says:
July 12, 2013 at 6:19 am
The Antarctic Circumpolar Current did start up at 34.6 million years ago as Australia/Tasmania separated from the continent. Antarctica rapidly glaciated over at this point in less than 100,000 years and glacial till/dropstones evidence indicates the glaciers extended right to the coast, partially onto the continental shelf at this time.
At about 26 million years ago, the Circumpolar Current between South America and Antarctica (this time) was disrupted again by the small cratons between them getting jostled around. The glaciers melted back by about half. The Current restarted at about 14 million years and Antarctica reglaciated at this time.
Here is a timeline of the events.
http://s22.postimg.org/804qp4xo1/Temp_Geography_45_Mys.png
Bill has stated the true current knowledge of Antarctica in the last 30 million years. The authors have been negligent or dishonest in not acknowledging this existing knowledge. They seem to have created a straw man to attack, implying that geologists consider Antarctic to have been continuously glaciated for 34 million years, when as Bill points out it is well known that Antarctica’s glaciation has been interrupted.
One gets the feeling that in a basement somewhere is a smoke-filled room where a “war council” plans a continuous onslaught against any climatic, geological and other scientific existing knowledge and research which shows factors other than CO2 to be drivers of climate, and seeks to direct propaganda against such research calling it into question. Now deep ocean circulation is in the firing line. They are trying to undermine the well established science concerning the strong effect of global ocean circulation patterns on climate and climate change.
The corpus of scientific knowledge need to be actively protected from political attack and transmitted to present and future generations intact.
George, I saw a mini series on it, but it would seem that at one time in the distant past, maybe 2 billion years ago, possibly the 250 million year marker was wrong. It was before the dinosaurs anyway. But regarding the evolution of primates, human precursors i.e., hominins etc., separated around the 4 million years marker from other higher primates. They couldn’t have done that if the planet was cold or ice bound everywhere. It was the natural environment that dictated their survival or demise. One of the catch phrases our archaeologists taught us. “Humans propose, but mother nature deposes”. We would not have survived so long in a hunter, gatherer and fisher economy without learning agriculture that allowed us to domesticate animals and produce food. This has not changed either. Bottom line is we adapted. But without crops and grazing animals and fish in the sea, we will starve. So who cares about what antarctic or the arctic dynamics where, how are we to cope with another ice age or mini ice age. It’s the here and now that is important. I think governments all around the world have more knowledge of what can happen than they want to admit and are conning people with all this inaccurate science (if you can call it that) not to tell the real truth. Anyway, I’m off to bake a roast lamb dinner, my home grown rhubarb tart, and Yorkshire puddings. And muddle over how the hell am I going to pay my electricity bill.
Dodgy Geezer
“The Argentines originally seem to have made a claim for it in the 1830s for strategic reasons”
I agree with much of your piece, but (to be a little pedantic) it wasn’t the ‘Argentines’ in 1830 as the country called Argentina didn’t become a federation of provinces (called Argentina) until 1861, in much the same way that the ‘US’ didn’t become the USA until 1776-1789.
As I pointed out earlier, this is an important point, because although the Argentines like to think of the Falklands as part of their country, it NEVER was! Britain declared sovereignty over the islands 28 years BEFORE Argentina existed. This seems to escaped people like actor Sean Penn and sunglasses-man Bono.
Ya-but, was there not a consensus at one time against continental drift?
Yes, somewhat like the consensus against natural climate cycles. Some of the reasons why continental drift was rejected are discussed here:
http://www.geoscience-environment.com/es767/index_es767.html
You know, if you look at that right…..could that be a crater? Against the spin or with?
But someone must have thought of that before.
Steve Garcia says:
July 13, 2013 at 12:13 am
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It needed to be said. thx.