Southern ocean

Southern Ocean to acidify much sooner than thought

11 November 2008

The Southern Ocean will acidify much earlier than previously thought from increasing atmospheric carbon dioxide levels, taking it past the point where the shells of sea creatures will start to dissolve, according to a new study.

That point will be reached when atmospheric carbon dioxide (CO2) levels pass 450 parts per million (ppm),  which is projected to occur within 30 years at most, according to University of New South Wales climate scientist Dr Ben McNeil.

Previous estimates found that this "dissolution point" for shells in the Southern Ocean would occur after atmospheric carbon dioxide concentrations reached 550ppm, which is projected to occur in the latter part of the century, says Dr McNeil, whose research with Dr Richard Matear is published in the US journal Proceedings of National Academy of Sciences.

By using a new technique that better quantifies natural variations of carbon dioxide in the Southern Ocean, they found that natural processes amplify the onset of the dissolution point.

"Oceanic acidification is a direct consequence of increasing atmospheric carbon dioxide concentrations," says Dr McNeil. "Our new results point to irreversible and detrimental impacts to Southern Ocean marine calcifying organisms if atmospheric CO2 exceeds 450ppm. 

"It provides additional and direct scientific evidence for the world to do everything in its power to limit CO2 concentrations to 450ppm in order to avoid the irreversible consequences associated with ocean acidification."

Many marine organisms produce calcium carbonate for protection and growth, particularly in the Southern Ocean. Harming the calcifying process could have significant consequences for the marine food chain, as earlier studies have shown, but these flow-on effects remain unclear.

The problem arises because rising atmospheric carbon dioxide concentrations will fundamentally alter the ocean's chemistry by lowering ocean pH, making it more acidic.

Of the 30 billion tonnes of carbon dioxide emitted into the atmosphere through fossil-fuel burning, about one-third is absorbed by the ocean.  There, it not only reduces seawater pH but also reduces carbonate mineral saturation, which plays an important role in calcification for many marine organisms.

Media contact:
Bob Beale: mobile 0411 705 435,  bbeale@unsw.edu.au

Latest news

The clean industrial revolution
So where does Australia’s economic future lie in this rapidly changing world? In this compelling book, climate scientist and economist Ben McNeil demonstrates the immense opportunities that will open up if Australia leads the new clean industrial revolution.

UNSW logo Winner of the 2009 Young Tall Poppy Science Award: Dr Donna Green
Dr Donna Green of CCRC is one of three Science Faculty scholars honoured at the 2009 Young Tall Poppy Awards hosted by the Australian Institute of Policy and Science..

Looming El Nino sets up gloomy forecast
South-east Australians can expect little relief from below average rainfall according to climate experts.

More news...

Antarctica

Reading past climates to see the future

With the massive Antarctic Circumpolar Current circling the Southern Ocean, largely preventing north-south flow across it and thereby isolating Antarctica from the subtropics, many scientists believe the existence of the Southern Ocean acts to cool Antarctica. But what other climate patterns might the Southern Ocean control?

Read more...

An addiction that fouls the air

Coal provides nearly 80 per cent of Australia's electricity needs. Not the US, Russia or even China has a bigger coal addiction, despite having vastly more coal reserves than Australia. The Australian Greenhouse Office says emissions from coal-dominated electricity generation rose 50 per cent between 1990 and 2004.

Read more...

Smoke stack

Bali or bust

The Bali Climate Declaration has made the scientific view on emissions targets patently clear. It is now over to the policy makers to give the planet a decent future.

Read more...

Ocean weather

The Big Engine: oceans and weather

Federation Fellow and 2008 Eureka Prize winner, Professor Matthew England of CCRC, on the latest research into the role oceans play on weather.

Read more...

UCC logo