Showing posts with label Carbon sinks. Show all posts

Written by fatih al-farahat in , , ,


Ozone hole has unforeseen effect on ocean carbon sink in the Southern Ocean

Ozone hole has unforeseen effect on ocean carbon sink

by Kate Ravilious, NewScientist, June 26, 2009

The Southern Ocean has lost its appetite for carbon dioxide, and now it appears that the ozone hole could be to blame.

The Antarctic ozone hole (Image: NASA / Goddard Space Flight Center / SVS)

The Antarctic ozone hole (Image: NASA / Goddard Space Flight Center / SVS)

In theory, oceans should absorb more CO2 as levels of the gas in the atmosphere rise. Measurements show that this is happening in most ocean regions, but strangely not in the Southern Ocean, where carbon absorption has flattened off. Climate models fail to reproduce this puzzling pattern.

The Southern Ocean is a major carbon sink, guzzling around 15% of CO2 emissions. However, between 1987 and 2004, carbon uptake in the region was reduced by nearly 2.5 billion tonnes – equivalent to the amount of carbon that all the world's oceans absorb in one year.

Premature effect

To figure out what is going on, Andrew Lenton, from the University of Pierre and Marie Curie in Paris, France, and his colleagues created a coupled ocean and atmosphere climate model, to investigate carbon absorption in oceans. Crucially, they included changes in the concentration of stratospheric ozone since 1975.

By running their model with and without the ozone depletion since 1975, Lenton and his colleagues were able to show that the ozone hole is responsible for the Southern Ocean's carbon saturation.

The effect could be down to the way decreasing stratospheric ozone and rising greenhouse gases are altering the radiation balance of the Earth's atmosphere. This has been predicted to alter and strengthen the westerly winds that blow over the Southern Ocean.

"We expected this transition to a windier regime, but it has occurred much earlier than we thought, seemingly because of the ozone hole," says Lenton.

'Unexpected effect'

Stronger surface winds enhance circulation of ocean waters, encouraging carbon-rich waters to rise from the deep, limiting the capability of surface water to absorb carbon from the atmosphere. Furthermore, the higher carbon levels in surface waters make them more acidic – bad news for many forms of ocean life, such as coral and squid.

"This result illustrates how complex the chain of cause and effect can be in the Earth system. No one would ever have predicted from first principles that increasing CFCs would have the effect of decreasing uptake of ocean carbon dioxide," says Andrew Watson, from the University of East Anglia, U.K.

Journal reference: Geophysical Research Letters (DOI: 10.1029/2009GL038227)

Link to article: http://www.newscientist.com/article/dn17385-ozone-hole-has-unforeseen-effect-on-ocean-carbon-sink.html

Written by fatih al-farahat in ,


A.D. Moy, W.R. Howard, S.G. Bray & T.W. Trull, Nature Geosci., Reduced calcification in modern Southern Ocean planktonic foraminifera, G. bulloides

Letter abstract

Nature Geoscience, published online 8 March 2009 | doi:10.1038/ngeo460

Reduced calcification in modern Southern Ocean planktonic foraminifera

Andrew D. Moy1,2, William R. Howard1, Stephen G. Bray1 and Thomas W. Trull1,3,4

Anthropogenic carbon dioxide has been accumulating in the oceans, lowering both the concentration of carbonate ions and the pH (ref. 1), resulting in the acidification of sea water. Previous laboratory experiments have shown that decreased carbonate ion concentrations cause many marine calcareous organisms to show reduced calcification rates2, 3, 4, 5. If these results are widely applicable to ocean settings, ocean acidification could lead to ecosystem shifts. Planktonic foraminifera are single-celled calcite-secreting organisms that represent between 25 and 50% of the total open-ocean marine carbonate flux6 and influence the transport of organic carbon to the ocean interior7. Here we compare the shell weights of the modern foraminifer Globigerina bulloides collected from sediment traps in the Southern Ocean with the weights of shells preserved in the underlying Holocene-aged sediments. We find that modern shell weights are 30–35% lower than those from the sediments, consistent with reduced calcification today induced by ocean acidification. We also find a link between higher atmospheric carbon dioxide and low shell weights in a 50,000-year-long record obtained from a Southern Ocean marine sediment core. It is unclear whether reduced calcification will affect the survival of this and other species, but a decline in the abundance of foraminifera caused by acidification could affect both marine ecosystems and the oceanic uptake of atmospheric carbon dioxide.
  1. Antarctic Climate and Ecosystems Cooperative Research Centre, Hobart, Tasmania 7001, Australia
  2. Department of the Environment, Water, Heritage and the Arts, Australian Antarctic Division, Kingston, Tasmania 7050, Australia
  3. University of Tasmania, Hobart, Tasmania 7001, Australia
  4. CSIRO Marine and Atmospheric Research, Hobart, Tasmania 7001, Australia

Correspondence to: William R. Howard1 e-mail: Will.Howard@utas.edu.au

Link to abstract: http://www.nature.com/ngeo/journal/vaop/ncurrent/abs/ngeo460.html

Written by fatih al-farahat in ,


Global warming from CO2 will increase 5-fold over the next millennium, University of Liverpool scientists predict

Global warming from CO2 will increase 5-fold over the next millennium, University of Liverpool scientists predict

ScienceDaily (Jan. 29, 2009) — Scientists at the University of Liverpool have found that heating from carbon dioxide will increase five-fold over the next millennium.

Scientists studied the impact that current carbon emissions have on the delicate balance between air and sea carbon exchange. They found that the ocean’s ability to store excessive amounts of carbon dioxide over thousands of years will affect the long-term heating of the planet.

The ocean acts as an enormous carbon sink which naturally absorbs any extra carbon dioxide added to the atmosphere. Its ability to store more carbon dioxide than both the atmosphere and land provides long-term storage for the carbon dioxide emitted by human activities.

Scientists at Liverpool, however, have found that if all conventional coal, oil and gas carbon reserves are exhausted, the excessive amounts of carbon dioxide in the atmosphere will begin to alter the ocean’s natural chemistry and hinder its ability to absorb and exchange the gas.

Professor Ric Williams, from the University’s School of Earth and Ocean Sciences, explains: “It is accepted that rising atmospheric carbon dioxide concentrations lead to an increase in heating around the globe. It was, however, unclear as to how the ocean’s ability to store carbon could affect the future overall heating of the earth.

“The excessive amount of carbon in the atmosphere will make the oceans more acidic and hamper the ability of the oceans to absorb further carbon from the atmosphere. The extra carbon dioxide remaining in the atmosphere will lead to an increase in the overall heating of our planet, making sea levels rise and exacerbating the melting of the Arctic ice caps.

“To prevent a situation like this from happening scientists are working to develop carbon-capture techniques, which aim to remove excess carbon from identifiable sites, such as the atmosphere around fossil fuel plants, and permanently store them away.”

The research, in collaboration with the University of East Anglia, The University of Bristol and Massachusetts Institute of Technology, is funded by the UK Natural Environment Research Council.