Researchers connect seawater chemistry with climate change, evolution

Jul 19, 2012
This is a satellite view of the Zagros mountain belt in western Iran. The range forms part of the most extensive belt of water-soluble gypsum on Earth, stretching from Oman to Pakistan, and well into Western India. Scientists suggest that the dissolution of ancient salt deposits caused drastic changes in seawater chemistry, which may have triggered long-term global cooling. Credit: US Geological Survey/Center for Earth Resources Observation and Science

Humans get most of the blame for climate change, with little attention paid to the contribution of other natural forces. Now, scientists from the University of Toronto and the University of California Santa Cruz are shedding light on one potential cause of the cooling trend of the past 45 million years that has everything to do with the chemistry of the world's oceans.

"Seawater chemistry is characterized by long phases of stability, which are interrupted by short intervals of rapid change," says Professor Ulrich Wortmann in the Department of at the University of Toronto, lead author of a study to be published in Science this week. "We've established a new framework that helps us better interpret evolutionary trends and over long periods of time. The study focuses on the past 130 million years, but similar interactions have likely occurred through the past 500 million years."

Wortmann and co-author Adina Paytan of the Institute of at the University of California Santa Cruz point to the collision between India and Eurasia approximately 50 million years ago as one example of an interval of rapid change. This collision enhanced dissolution of the most extensive belt of water-soluble on Earth, stretching from Oman to Pakistan, and well into Western India – remnants of which are well exposed in the Zagros mountains.

This is the Zagros mountain belt in western Iran as seen from the space shuttle Atlantis. The range forms part of the most extensive belt of water-soluble gypsum on Earth, stretching from Oman to Pakistan, and well into Western India. Scientists suggest that the dissolution of ancient salt deposits caused drastic changes in seawater chemistry, which may have triggered long-term global cooling. Credit: Photo courtesy of NASA

The authors suggest that the dissolution or creation of such massive gyspum deposits will change the sulfate content of the ocean, and that this will affect the amount of sulfate aerosols in the atmosphere and thus climate. "We propose that times of high sulfate concentrations in ocean water correlate with global cooling, just as times of low concentration correspond with greenhouse periods," says Paytan.

"When India and Eurasia collided, it caused dissolution of ancient salt deposits which resulted in drastic changes in seawater chemistry," Paytan continues. "This may have led to the demise of the Eocene epoch – the warmest period of the modern-day Cenozoic era – and the transition from a greenhouse to icehouse climate, culminating in the beginning of the rapid expansion of the Antarctic ice sheet."

The researchers combined data of past seawater sulfur composition, assembled by Paytan in 2004, with Wortmann's recent discovery of the strong link between marine sulfate concentrations and carbon and phosphorus cycling. They were able to explain the seawater sulfate isotope record as a result of massive changes to the accumulation and weathering of gyspum – the mineral form of hydrated calcium sulfate.

"While it has been known for a long time that gyspum deposits can be formed and destroyed rapidly, the effect of these processes on seawater chemistry has been overlooked," says Wortmann. "The idea represents a paradigm shift in our understanding of how ocean chemistry changes over time and how these changes are linked to climate."

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More information: "Rapid Variability of Seawater Chemistry over the Past 130 Million Years," Science, 2012.

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Caliban
3 / 5 (2) Jul 19, 2012
This mechanism will require a massive amount of additional study before anything definitive can be said about how pronounced or prolonged an effect sulfate concentration in seawater has on climate at any timescale.

This same process(in addition to many more) must have occurred over and over again, for a lot longer than .5GY, throughout geological time as tectonic and volcanic forces have created and torn apart seas, mountains and continents again and again in the constant presence of the forces of weathering and erosion.

To isolate this single process(though it isn't explicity presented as such) as the "smoking gun" for current GW is disingenuous, and that's only if we are charitable -this, assuming that this abstraction of the findings is accurately represented in this article.

Parsec
5 / 5 (3) Jul 19, 2012
To isolate this single process(though it isn't explicity presented as such) as the "smoking gun" for current GW is disingenuous, and that's only if we are charitable -this, assuming that this abstraction of the findings is accurately represented in this article.

This article is talking about changes over millions of years. The current GW is on the order of a dozen decades or maybe a little more. As a consequence, I suspect that nothing is this article has anything whatsoever to do with our current GW.
Caliban
3.5 / 5 (2) Jul 20, 2012
"We propose that times of high sulfate concentrations in ocean water correlate with global cooling, just as times of low concentration correspond with greenhouse periods," says Paytan.


Parsec,

What, then, does the above quoted passage say to you? Do you think that they mean to decouple this ocean chemistry process from the current warming trend? That a mechanism that has been operative over and over in the past has suddenly stopped operating in the present?

Try another reading of the article while keeping this in mind.

Claudius
2.6 / 5 (5) Jul 20, 2012
Humans get most of the blame for climate change, with little attention paid to the contribution of other natural forces.


This statement seems to demonstrate that there is an incomplete understanding of what changes the climate, with humans getting most of the blame. With such an incomplete understanding, blaming humans is mostly political. Res ipsa loquitur.
rubberman
5 / 5 (1) Jul 24, 2012
Humans get most of the blame for climate change, with little attention paid to the contribution of other natural forces.


This statement seems to demonstrate that there is an incomplete understanding of what changes the climate, with humans getting most of the blame. With such an incomplete understanding, blaming humans is mostly political. Res ipsa loquitur.


Um...no. The above statement would be true if we could find ANY correlation between the current change in climate and any type of natural forcing that could be responsible for the changes we are observing...we cant.....other than us.

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