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Southern Ocean back in business as a carbon sink (models were wrong)

The Southern Ocean absorbs 40% of the global oceanic uptake in CO2. For most of the last ten years researchers thought it was weaker, or at “saturation” point and not able to absorb more CO2. Instead, it looks like it has been absorbing more again and by the year 2010 was back up to full power. This means there was a lot more natural variation than scientists (and their models) thought.The GCM’s are meant to be able to predict the oceans.

Back in 2007, New Scientist broadcast that the slowdown has “far reaching implications”, things were worse than the IPCC’s projections. Things were 20 years ahead of the IPCC’s schedule and it was “scary”. Instead the IPCC was 20 years behind real life, and the models were as bad as the skeptic projected. Will New Scientist tell the world?

Southern Ocean already losing ability to absorb CO2

By Catherine Brahic, New Scientist 2007

One of the world’s largest carbon sinks has stopped soaking up the carbon dioxide that humans are pumping into the atmosphere, according to a new study.

Global warming has caused the Southern Ocean to become windier, churning up the waters so that they are unable to absorb CO2 at the rate we produce it, the researchers say.

The implications are far-reaching, and once more imply that the Intergovernmental Panel on Climate Change’s projections are conservative: temperatures are likely to rise higher than predicted.

“To me, it is quite scary that we can detect this impact of climate change already,” says Le Quéré. By releasing more CO2 into the atmosphere, people are participating in a “large and dangerous experiment”, she says.

The news of the “reinvigoration” on Science Daily:

“From the year 2005, however, scientists pointed out that the Southern Ocean carbon sink might have begun to “saturate.” Based on model results, they suggested that it had not increased since the late 1980s. This was unexpected as one had assumed that a direct relationship existed between the magnitude of the carbon sink and the concentration of atmospheric CO2: the higher the concentration of CO2 in the air, the greater the amount of CO2 absorbed by the sea.

Now the tables have turned. Since the beginning of the millennium the Southern Ocean carbon sink has become much stronger, thereby regaining its expected strength. This is demonstrated by an international research team led by Nicolas Gruber, a professor of environmental physics at ETH Zurich, and his postdoc Peter Landschützer in a study recently published in Science.”

It may involve the PDO, and El Nino phenomenon, (nearly everything else does) and the very last line says it may explain  “the pause” (ditto for that too).

Future trends cannot be predicted reliably

At present, the two researchers are unable to predict how the net carbon uptake of the Southern Ocean is likely to evolve in the future. “Our statistical model is not able to predict the future development,” says Landschützer, “so it is very critical to continue measuring the surface ocean CO2 concentrations in the Southern Ocean. “This is particularly important since current models are not able to reproduce the observed variations,” adds Gruber. Hence, long-term datasets are the only reliable means for determining the future evolution of the ocean’s sink for carbon.

Another factor that is not yet fully understood is the effect of large-scale climate phenomena such as El Niño and La Niña on the Southern Ocean carbon sink. It is particularly noticeable that the reinvigoration of the carbon sink coincides with a period of prevalent La Niña conditions, i.e., relatively cool sea surface temperatures in the Pacific. The reinvigoration of the ocean’s carbon sink also occurred during a period when global air temperatures have changed very little — the so-called climate warming hiatus — possibly related to a stronger heat uptake by the ocean.

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