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Coral cores and ocean-atmosphere oscillations

Ocean-atmosphere oscillations are naturally occurring cycles affecting sea surface temperature and precipitation. They are among the key reasons why some years are dry and plagued by drought while other years it rains incessantly resulting in widespread flooding. Examples such as the El Niño-Southern Oscillation have been well-studied and linked to periodic droughts or flooding on opposite sides of the Pacific.

Increased levels of CO2 in the atmosphere, due in large part to human activity, could exacerbate these extreme weather events by impacting ocean-atmosphere oscillations and other natural processes. To predict how these processes might be affected, the IAEA Environment Laboratories have brought together scientists from around the world to examine corals using nuclear and isotopic techniques to see how the climate behaved under past conditions. This information helps Member States develop more accurate and complete models to predict and manage consequences of increased atmospheric CO2.

The ocean-climate system is sometimes said to ‘ring like a bell’ given its natural cycles and oscillations. However, rising CO2 levels in the atmosphere, due to increased emissions, are changing natural processes like ocean-atmosphere oscillations in ways that may produce more intense and disruptive weather events. If the ocean-climate system ‘rings like a bell,’ how will the ring of the bell change when it is hit with the hammer of a high CO2 world?

To understand the impact of atmospheric CO2 emissions on ocean-atmosphere oscillations, the IAEA Environment Laboratories are working with scientists in Member States to examine how these oscillations have behaved under different climate conditions in the past.  By using nuclear and isotopic techniques, scientists can investigate the carbonate growth bands in cores from coral skeletons. Just like the rings in a tree trunk, carbonate growth bands in corals can serve as a historical record of climate conditions. Laid down chronologically in the skeletons of corals, these bands contain nuclear tracers, isotopic ratios and geochemical markers that scientists can use as proxies to determine the date and climactic conditions of the time the bands were formed. Investigating historical trends in conditions like temperature, pH and rainfall is critical to understanding how ocean-atmosphere oscillations may change in a high CO2 world. 

Information on the past behaviour of natural climatic processes can contribute to the development of more reliable and robust models that help Member States predict how increased atmospheric CO2 emissions will affect ocean-atmosphere oscillations and subsequent weather patterns all over the world.  

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