The Environmental Impact of the Southern Ocean

The Ocean Surrounding Antarctica Losing its Ability as a Carbon Sink

Jan 21, 2009 Laurence O'Sullivan

The diminishing ability of the Southern Ocean to act as a carbon sink has negative environmental impacts both on the ocean itself and on the global environment.

With ever increasing atmospheric CO2 emissions, natural carbon sinks such as tropical rain forests and the oceans play an important environmental role in absorbing carbon dioxide from the atmosphere. The oceans of the world absorb a large proportion of man made carbon dioxide and none more so than the Southern Ocean. Saturation of these carbon sinks will have large environmental impacts.

Global Environmental Importance of the Southern Ocean

A report titled “Acid Test”, published by Oceania in October 2008 shows how the oceans absorb over 30% of global carbon emissions, mitigating some of the climate change that would otherwise have occurred.

Figures from “Saturation of the Southern Ocean CO2 Sink due to Recent Climate Change” by Corinne Le Quéré and published in Volume 316 of the journal Science in June2007 show that the Southern Ocean is responsible for over half of all oceanic absorption of CO2.

“The Southern Hemisphere Westerlies in a Warming World” by Joellen Russell, published in Vol. 19 of the Journal of Climate in December 2006 states “The Southern Ocean is the cross-roads of the global ocean’s water masses, connecting the Atlantic, Pacific, and Indian Oceans as well as connecting the deep ocean to the surface.”

“Effect of Natural Iron Fertilization on Carbon Sequestration in the Southern Ocean”, published in Vol. 446 of the journal Nature in April 2007 states that “The Southern Ocean plays a major role in the climate system, and is recognized as the oceanic body most sensitive to climate change”.

Saturation of the Southern Ocean

Corinne Le Quéré, in her Science article states that “the Southern Ocean sink of CO2 has weakened between 1981 and 2004 by 0.08 petagrams of carbon per year per decade relative to the trend expected from the large increase in atmospheric CO2”. In this report she surmises that the saturation could be caused by ocean disturbance, caused by the increased winds due to the man made ozone layer hole over the Antarctic. “Southern Ocean Acidification” by B. McNeil and J. Matear, published by the “Proceedings of the National Academy of Sciences” (PNAS) in December 2008, states “Oceanic absorption of anthropogenic CO2 has lowered the pH and concentration of carbonate ion substantially since preindustrial times”.

Environmental Impact of Southern Ocean Saturation

Carbon dioxide saturation of the Southern Ocean has both local and global environmental ramifications. The report “Acid Test” states that “Many species will be unable to adapt to the rapid changes in ocean acidity and carbonate concentrations, especially those that build calcium carbonate shells and skeletons. This may lead to population crashes in many species, including oysters, mussels, crabs and lobsters”. “Contributions to Accelerating Atmospheric CO2 Growth”, by Canadell et al. published by the PNAS in Vol. 104, November 2007, states that “In the Southern Ocean, the poleward displacement and intensification of westerly winds caused by human activities has enhanced the ventilation of carbon-rich waters normally isolated from the atmosphere at least since 1980, and contributed nearly half of the decrease in the ocean CO2 uptake.”

Just like changes in the Arctic environment, what happens in the Antarctic does not stay in the Antarctic. Should the Southern Ocean become an emitter of carbon dioxide rather than a carbon sink then the global environmental consequences could be disastrous. Environmental effects of climate change, measured by bodies such as the Intergovernmental Panel on Climate Change, are largely based on present day scenarios. The loss of the largest ocean carbon sink would wreak havoc with these environmental predictions.

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