New study to investigate the impacts of ocean acidification in the Southern Ocean

07 January 2013

To begin 2013 with a big bang, a team of thirty scientists, from eight of the UK’s top research laboratories, will be setting out on an oceanographic mission to study the effect of ocean acidification in waters near Antarctica. The five week long research cruise, aboard the Natural Environment Research Council’s RRS James Clark Ross, departs on 8^th January for some of the coldest waters on Earth.

The ocean is an integral part of the climate system. By absorbing large amounts of the carbon dioxide (CO₂), mostly produced as result of our use of fossil fuels, the ocean helps to slow the rate and severity of climate change. The global ocean has absorbed more than 30% of the total CO₂ produced by human activities in the past 200 years. While this can be seen as a benefit, the down side is that as the ocean absorbs more and more CO₂ its chemistry changes and the seawater moves down the pH scale towards acidity. This process is known as ocean acidification.

Cold waters provide best indications

Cold waters naturally hold more CO₂ than warmer waters so the icy Southern Ocean is expected to be especially informative for studying the effects of ocean acidification. Additionally, deep-water upwelling around Antarctica brings water to the surface that already contains very high levels of CO₂. For these reasons, the waters of the Southern Ocean are likely to provide a unique window into how the marine environment will respond to higher CO₂ levels in the future. This expedition will include a visit to the Weddell Sea, which has some of the coldest surface waters (1.8°C) anywhere in the world.

During the expedition, scientists will study the impact of the changing chemistry on marine organisms and ecosystems, on the cycling of carbon and nutrients in the sea and on how the sea interacts with the atmosphere to influence climate.

Parallel investigations

Firstly, the researchers will look at how ecosystems vary between locations where the chemistry of seawater is naturally more acidic and those where it is more alkaline.  This approach will provide insights on how acidification may affect organisms living in their natural environment, where natural selection and adaptation have had time to play out.

A second approach is experimental, using tanks of natural seawater collected from the upper ocean and brought into controlled conditions on deck. This natural seawater will be subjected to various levels of carbon dioxide that are likely to occur in the future.

Dr Geraint Tarling, a British Antarctic Survey Researcher and the leader of this expedition says: “This is the most comprehensive investigation into the response of the Southern Ocean ecosystem to ocean acidification yet mounted. The investigative team encompasses some of the most experienced marine researchers from the UK. The team will not only look at how different parts of the ecosystem respond in isolation, but also see how effects interact to produce an ecosystem-level response. The work on this expedition will build on recent evidence of ocean acidification dissolving the shells of marine snails, known as pteropods, in the Southern Ocean that was recently published in Nature Geoscience (*for reference, please see left hand column).

Professor Toby Tyrrell from the National Oceanography Centre and coordinator of the UKOA Sea Surface Consortium added: “Another reason for visiting the Southern Ocean is that it is also an unusually stable environment, with surprisingly little seasonal variation. The sea remains extremely cold even in summer. As the local organisms are not exposed to much natural variation, they could be more susceptible to human-induced variations. It is important for us to find out whether this supposition is correct.”