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article imageCarbon release contributed to end of last Ice Age

By Robert Myles     Feb 12, 2015 in Environment
Southampton - Carbon dioxide released from the ocean deeps contributed to ending the last Ice Age, it’s emerged from a new study led by the UK's University of Southampton.
Their newly published research demonstrated that carbon stored in an isolated reservoir in the Southern Ocean escaped into the atmosphere. As a result, atmospheric CO2 levels rose resulting in an increase in global temperatures.
The findings, published in Nature, will give climate scientists and modellers insights into how Earth’s oceans affect the carbon cycle and climate change.
Earth is currently going through a warmer period, known as an interglacial. Concentrations of CO2 in the atmosphere show a marked difference during interglacial periods as against ice ages. Atmospheric CO2 levels fluctuate from about 185 parts-per-million (ppm) during ice ages, to around 280 ppm during interglacials.
According to the researchers, Earth’s oceans currently contain roughly 60 times more carbon than the atmosphere. But that carbon, at least in geological timescales, can exchange rapidly between atmosphere and ocean.
The University of Southampton’s Dr Miguel Martínez-Botí, joint lead-author of the study commented,
"The magnitude and rapidity of the swings in atmospheric CO2 across the ice age cycles suggests that changes in ocean carbon storage are important drivers of natural atmospheric CO2 variations.
"Our findings support the theory that a series of processes operating in the southernmost sector of the Atlantic, Pacific and Indian Oceans, a region known as the 'Southern Ocean', changed the amount of carbon stored in the deep-sea.”
Dr Martínez-Botí went on to explain that while a reduced interchange between the two systems operating in the Southern Ocean — the deep-sea and the atmosphere — potentially locked atmospheric carbon away in the ocean abyss, during the warmer interglacial periods that process went into reverse. That resulted in higher atmospheric CO2 concentrations.
The team of researchers, drawn from the Autonomous University of Barcelona and the Australian National University as well as University of Southampton, looked at the composition of the calcium carbonate shells of ancient marine organisms. At one time, thousands of years ago, the habitat of these organisms was the surface of the ocean. Analysis of these ancient shells allowed the researchers to trace its carbon content.
From the chemical makeup of these shells, researchers could calculate the acidity of the seawater they inhabited and, from that, the amount of carbon dioxide contained in these ancient seas.
"We found that very high concentrations of dissolved CO2 in surface waters of the Southern Atlantic Ocean and the eastern equatorial Pacific coincided with the rises in atmospheric CO2 at the end of the last ice age, suggesting that these regions acted as sources of CO2 to the atmosphere,” said joint lead author Dr Gianluca Marino, from the Australian National University.
Co-author Dr Gavin Foster, from the University of Southampton, commented,
"Just like the way the oceans have stored around 30 per cent of humanity's fossil fuel emissions over the last 100 years or so, our new data confirms that natural variations in atmospheric CO2 between ice ages and warm interglacials are driven largely by changes in the amount of carbon stored in our oceans.
"While our results support a primary role for the Southern Ocean processes in these natural cycles, we don't yet know the full story and other processes operating in other parts of the ocean, such as the North Pacific, may have an additional role to play."
Although Earth’s oceans currently act as a CO2 sink for carbon dioxide emissions, locking up about one-third of fossil fuel emissions, as global temperatures increase, so warming the oceans, scientists predict the oceans ability to absorb similar levels of CO2 will be diminished. Thus, more CO2 would remain in the atmosphere, rather than being locked away, a process that could exacerbate global warming.
More about carbon release, Ice age, Carbon dioxide, university of southampton, CO2 Emissions
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