Geobiologists uncover links between ancient climate change and mass extinction

January 27, 2011 by Marcus Woo, California Institute of Technology
This is rock strata on Anticosti Island, Quebec, Canada, one of the sites from which the researchers collected fossils. Credit: Woody Fischer

About 450 million years ago, Earth suffered the second-largest mass extinction in its history—the Late Ordovician mass extinction, during which more than 75 percent of marine species died. Exactly what caused this tremendous loss in biodiversity remains a mystery, but now a team led by researchers at the California Institute of Technology (Caltech) has discovered new details supporting the idea that the mass extinction was linked to a cooling climate.

"While it's been known for a long time that the is intimately tied to climate change, the precise mechanism is unclear," says Seth Finnegan, a postdoctoral researcher at Caltech and the first author of the paper published online in Science on January 27. The mass extinction coincided with a glacial period, during which global temperatures cooled and the planet saw a marked increase in glaciers. At this time, North America was on the equator, while most of the other continents formed a supercontinent known as Gondwana that stretched from the equator to the South Pole.

By using a new method to measure ancient temperatures, the researchers have uncovered clues about the timing and magnitude of the glaciation and how it affected ocean temperatures near the equator. "Our observations imply a climate system distinct from anything we know about over the last 100 million years," says Woodward Fischer, assistant professor of geobiology at Caltech and a coauthor.

The fact that the extinction struck during a glacial period, when huge ice sheets covered much of what's now Africa and South America, makes it especially difficult to evaluate the role of climate. "One of the biggest sources of uncertainty in studying the paleoclimate record is that it's very hard to differentiate between changes in temperature and changes in the size of continental ice sheets," Finnegan says. Both factors could have played a role in causing the mass extinction: with more water frozen in ice sheets, the world's sea levels would have been lower, reducing the availability of shallow water as a marine habitat. But differentiating between the two effects is a challenge because until now, the best method for measuring ancient temperatures has also been affected by the size of ice sheets.

The researchers analyzed the chemistry of fossils to determine the temperature during the Late Ordovician period. Shown are fossilized shells, brachiopods, trilobites, and gastropods, with a hammer for scale. Credit: Woody Fischer

The conventional method for determining ancient temperature requires measuring the ratios of oxygen isotopes in minerals precipitated from seawater. The ratios depend on both temperature and the concentration of isotopes in the ocean, so the ratios reveal the temperature only if the isotopic concentration of seawater is known. But ice sheets preferentially lock up one isotope, which reduces its concentration in the ocean. Since no one knows how big the ice sheets were, and these ancient oceans are no longer available for scientists to analyze, it's hard to determine this isotopic concentration. As a result of this "ice-volume effect," there hasn't been a reliable way to know exactly how warm or cold it was during these glacial periods.

But by using a new type of paleothermometer developed in the laboratory of John Eiler, Sharp Professor of Geology and professor of geochemistry at Caltech, the researchers have determined the average temperatures during the Late Ordovician—marking the first time scientists have been able to overcome the ice-volume effect for a glacial episode that happened hundreds of millions of years ago. To make their measurements, the researchers analyzed the chemistry of fossilized marine animal shells collected from Quebec, Canada, and from the midwestern United States.

The Eiler lab's method, which does not rely on the isotopic concentration of the oceans, measures temperature by looking at the "clumpiness" of heavy isotopes found in fossils. Higher temperatures cause the isotopes to bond in a more random fashion, while low temperatures lead to more clumping.

"By providing independent information on ocean temperature, this new method allows us to know the isotopic composition of 450-million-year-old seawater," Finnegan says. "Using that information, we can estimate the size of continental ice sheets through this glaciation." And with a clearer idea of how much ice there was, the researchers can learn more about what Ordovician climate was like—and how it might have stressed marine ecosystems and led to the extinction.

"We have found that elevated rates of climate change coincided with the mass extinction," says Aradhna Tripati, a coauthor from UCLA and visiting researcher in geochemistry at Caltech.

The team discovered that even though tropical ocean temperatures were higher than they are now, moderately sized glaciers still existed near the poles before and after the mass extinction. But during the extinction intervals, glaciation peaked. Tropical surface waters cooled by five degrees, and the ice sheets on Gondwana grew to be as large as 150 million cubic kilometers—bigger than the glaciers that covered Antarctica and most of the Northern Hemisphere during the modern era's last ice age 20,000 years ago.

"Our study strengthens the case for a direct link between and extinction," Finnegan says. "Although polar glaciers existed for several million years, they only caused cooling of the tropical oceans during the short interval that coincides with the main pulse of mass extinction."

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Display comments: newest first

1.8 / 5 (22) Jan 27, 2011
Any paper with the word "Climate Change" in it should be considered suspect. They are just trolling for grant money.

How sad. A whole profession grubbing for money and squandering centuries of respect.
2 / 5 (5) Jan 27, 2011
Very interesting find. Now they should look to the relation between these glacial periods and the rise and set of seawaterlevel. Some 15 thousant years ago, during the small ice age, sea levels where 120 meter lower than today. A lot more land was availeble all over the world making it generally speaking a good time for all living species. This relation between sealevel and iceages has evidently also a dramatic imput on the the ever changing climat. Strange that people have such a problem with climatchange these days. Don't they know that there has never been a stable climat on earth. It is not an invention of the human mind but the way things evolve on planet earth. We can try to understand the underliying processes of these changes, and we maybe don't have it always right. But the changes are there. They belong to the reality. If someone can't deal with the change factor in the world where you live on, he needs a realitycheque.
2.6 / 5 (15) Jan 27, 2011
Gosh, could this mean climate changes and man didn't cause it. I thought we were told climate could only change because of what man does and the climate we have had for the last 1000 years was the only correct climate.
Don't fight climate change, prepare for it. The only thing constant about climate IS change.
1.6 / 5 (13) Jan 27, 2011
Yes, Earth's climate is always changing.

Why? Earth's heat source is variable:

1. "Earth is connected gravitationally, magnetically and electrically to its heat source - a neutron star that is obscured from view by waste products in the photosphere. Neutron repulsion is like the hot filament in an incandescent light bulb." [Neutron repulsion, The APEIRON Journal,in press, 2011, 19pp.]

2. We propose an effective mechanism of solar dynamo-geodynamo connection which plays the role of the solar power pacemaker of the Earth
global climate ["Solar dynamo as host power pacemaker of the Earth global climate"]

With kind regards,
Oliver K. Manuel
2.6 / 5 (8) Jan 28, 2011
""While it's been known for a long time that the mass extinction is intimately tied to climate change, the precise mechanism is unclear," says Seth Finnegan, "

Ah come ON, Seth. It's been theorized. The theory has even been widely accepted. It has not been KNOWN.
Really? You are a doctoral candidate?
2.7 / 5 (7) Jan 28, 2011
a neutron star that is obscured from view by waste products in the photosphere. Neutron repulsion is like the hot filament in an incandescent light bulb.


I'll have a read of your paper Oliver. It just seems like a very different concept, if we were wrong about the sun then we are very wrong! And it seems unlikely that nobody has picked up on it until now. But if you believe there is compelling evidence to support this theory then by all means enlighten us :)
1 / 5 (3) Jan 28, 2011
Sorry Bob I gave you a low rating by mistake. Should have been a five.
3 / 5 (4) Jan 28, 2011
@Mathie - I think we all know that climate changes over time. The current concern with (primarily) carbon output is that 'we' are causing a very rapid change. If we are, then we need to change what we are doing. There is enough coal in the earth that we can keep burning it for centuries, if not a millenium. Should we do so?
1 / 5 (5) Jan 28, 2011
I'll have a read of your paper Oliver. It just seems like a very different concept, if we were wrong about the sun then we are very wrong! And it seems unlikely that nobody has picked up on it until now. But if you believe there is compelling evidence to support this theory then by all means enlighten us :)

Thanks, Bob,

Hyperlinks can't be posted here. Send me a message and I'll reply with the link.

not rated yet Jan 29, 2011

Hyperlinks can't be posted here.

Post them as, say "www DOT vectorsite DOT net/somedoc.html" -- a bit clumsy, but people can figure it out.
1 / 5 (3) Jan 29, 2011
not rated yet Jan 29, 2011

The link doesn't work. Though I suspect you know that and are just being a nut.
1.7 / 5 (6) Jan 29, 2011
Ha,Ha heres a link for you also,75 percent of the marine eco system is going to be depleted again very shortly,as the reset button has been pressed.
Notice those birds and fish dieing at "Nodal Points" around the globe??
Thats just the start,when the sphere obstructing the flow goes"retrograde" this place is gonna COOK.
Its YOUR fault,certain "Ones" did something very damaging against "Us" and "Us" engaged a sphere with a Kill tone for certain processer frequencies that stops the "Brain" cold,just like those birds and fish.
You screw with the science department,and they will screw with you,but we are grid scientists,and you are not.
Like I said before, those certain someones must return our science case and our money,and we "Might" tell you how to abate the tone coming in that is set to kill over 6 billion little bastards that screwed with us.
1 / 5 (3) Jan 29, 2011

The link doesn't work. Though I suspect you know that and are just being a nut.

db (DOT) tt/9SrfTiZ without spaces works when I copy and paste it.

Please try again - Oliver
2.3 / 5 (3) Jan 30, 2011
Hey Doc, you off your meds again???
1 / 5 (1) Jan 30, 2011
Please try again

"Pull my finger."
5 / 5 (1) Jan 30, 2011
Yes I agree that doc must have missed his medication. We should however feel sorry for him.
Perhaps a nice safe padded room where he cannot hurt himself might be in order.
He need not be alone, he could take notparker with him.
They sound like soul mates.
1 / 5 (2) Jan 30, 2011
Geez,You mean I am approved for Meds?
This is glorious news,I'm gonna go tell my Mom,she might be able to get approved now too.
And the implication that someone in the audience has empathy just brings me to tears too, LETS ALL HAVE A MOMENT .
And Geez oh Peet,an expert on soul mates is on board,we all feel so,so blessed.
Is Twit in the abridged version?
1 / 5 (1) Jan 31, 2011
Somebody asks Oliver for evidence and he posts a link for wikipedia about Ductility. Makes less sense than usual for Oliver. Tried it again with a different way of misinterpreting the botched link. This time got Oliver's usual crap.

But for those who really want to read the same exact thing Oliver has posted umpteen times without it ever proving his position here are both possible interpretations.

dbDOTtt/9SrfTiZ interpreted as db tt/9SrfTiZ space removed


dbDOTtt/9SrfTiZ interpreted replacing DOT with a '.'.

httpDELETEME:// Neutron repulsion.pdf

And I think it is pretty clear what to delete in both those links.

Now if Oliver behaves as usual he won't learn from this post as it would kill him to learn anything from me. Like doing actual experiments to find out how things really work. Or at least reading experiments that have already been done.

The iron stacks the fail to support him.


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