Climate: How much acidification can the oceans take?

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Rising CO2 concentrations present fundamental threat to oceans.

Current rate of acidification similar to changes during ancient extinction event

Staff Report

FRISCO — Climate scientists are constantly looking at the past to try and understand the present and forecast the future, and new study by University of Edinburgh researchers offers some worrisome clues about the current rate of ocean acidification.

After tracing changes in ocean chemistry that happened more than 250 million years ago, the scientists said that today’s rate of ocean acidification is similar to changes that led to the greatest known extinctions of marine life during the so-called Permian-Triassic Boundary extinction, which wiped out more than 90 per cent of marine species and more than two-thirds of the animals living on land.

Those changes were probably caused when extreme volcanic activity released huge amounts of carbon dioxide that ended up in the oceans, making them more acidic  with catastrophic consequences for life on Earth.

Scientists have long suspected that an ocean acidification event occurred during the greatest mass extinction of all time, but direct evidence has been lacking until now,” said Dr. Matthew Clarkson, of the University of Edinburgh’s School of GeoSciences who co-ordinated the study. “This is a worrying finding, considering that we can already see an increase in ocean acidity today that is the result of human carbon emissions.”

The amount of carbon added to the atmosphere that triggered the mass extinction was probably greater than today’s fossil fuel reserves, but the carbon was released at a rate similar to modern emissions. This fast rate of release was a critical factor driving ocean acidification, researchers say.

The Permian-Triassic Boundary extinction took place over a 60,000 year period. Acidification of the oceans lasted for around 10,000 years. Oceans can absorb some carbon dioxide, but the large volume and high release rate released changed the chemistry of the oceans, the researchers said.

The findings are based on a chemical analyis of rocks unearthed in the United Arab Emirates, which were on the ocean floor at the time. The rocks preserve a detailed record of changing oceanic conditions at the time.

The study, published in the journal Science, was carried out in collaboration with the University of Bremen, Germany, and the University of Exeter, together with the Universities of Graz, Leeds, and Cambridge.

Funding was provided by the International Centre for Carbonate Reservoirs, Natural Environment Research Council, The Leverhulme Trust, German Research Foundation and the Marsden Fund.

 

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