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Link between climate change and Gibraltar Currents over 6 million years discovered

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CO2 levels now higher than any time in the last 23 million years

One of the most pressing messages that climate scientists attempt to convey to the public is how today’s CO2 levels compare to those of the Geologic past. Such comparisons can provide public context for current CO2 rise, as well as important information on the response of global temperatures to rising CO2. A new study published in Geology suggests that present-day CO2 levels (412 ppmv) are now likely higher than at any time in at least the last 23 million years!

In this newly published study, a team led by Brian Schubert, Associate Professor in the School of Geosciences at the University of Louisiana at Lafayette, used the remains of dead plants to produce a new record of atmospheric CO2 that spans 23 million years of uninterrupted Earth history. Their findings relied on the nearly continuous record of terrestrial photosynthesis provided by organic matter accumulated from partially decomposed plants.

“When plants grow, the relative amount of the two stable isotopes of carbon, carbon-12 and carbon-13, changes in response to the amount of CO2 in the atmosphere,” says Schubert. “One can therefore measure the relative amount of these two isotopes and calculate the CO2 concentration under which the plants grew.”

The remains of land plants can be used to calculate the amount of CO2 in Earth’s atmosphere. Photo credit: A. Hope Jahren

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Two Graduate Students win the GSA Graduate Research Grant

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The School of Geosciences wins prestigious Field Camp Award

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Examination of core samples extracted off the coast of Spain and Portugal shows definite proof of shifts in climate change since about six million years ago, and also provides new evidence of a deep-earth tectonic pulse in the region, according to a team of international scientist that includes Carl Richter, a School of Geosciences researcher.


Richter is one of 35 scientists from 14 countries who participated in Integrated Ocean Drilling Program Expedition 339. From November 2011 to January 2012, they worked on board "JOIDES Resolution," a research vessel. The team’s findings were published in the June 13, 2014 issue of "Science" magazine.


Working on board the research vessel JOIDES Resolution, the team took core samples from a three-mile stretch near the Strait of Gibraltar, which is a gateway between the Atlantic Ocean and the Mediterranean Sea. They then examined the sedimentary record produced there by strong ocean currents, commonly called Mediterranean outflow water through the Gibraltar gateway.


“Our initial goal was to understand how the Strait of Gibraltar acted first as a barrier and then as a gateway over the past 6 million years as the currents passed through the area,” Richter said. “Because the Mediterranean outflow water is saltier and heavier than the Atlantic waters, it plunges more than 3,000 feet downslope, carving deep-sea channels, and building up mountains of mud in these unique underwater landscapes. We now have first results for understanding the history of these currents through the Gibraltar gateway.”


Richter said the sediments collected during the expedition indicate that “oceans and climate are closely linked.”


Further analysis showed that the sediments contained far more sand than expected. A sheet of sand extends about 60 miles from the Gibraltar gateway; it is evidence of the strength and velocity of Mediterranean currents.
The research team’s findings could impact future oil and gas exploration, according to the geologist.


“The thickness, extent, and properties of these sands make them an ideal target in places where they are buried deeply enough to allow for the trapping of oil and gas,” he said.
The research team’s abstract notes: “These sands represent a completely new and important exploration target for potential oil and gas reservoirs.”


Expedition 339 was funded by the U.S. National Science Foundation and implemented by the Integrated Ocean Drilling Program – U.S. Implementing Organization.

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