- The factors that determine climate are complex. Oceans store about one quarter of the carbon dioxide (CO2) emitted through human activities, and play an important role in limiting impacts of climate change.
- Increasing carbon emissions and rising temperatures are disrupting oceanic processes, with potentially major consequences for marine ecosystems, the global climate, shoreline protection and coastal industries such as fisheries and tourism.
- In order to understand and anticipate potential changes in the climate, it is important to understand the processes involved in the global carbon cycle.
- Increasing levels of CO2 in the atmosphere cause global warming leading to ocean temperature increase, but also ocean acidification, sometimes referred to as ‘the other CO2 problem’ alongside climate change.
- The IAEA supports Member States in using radioisotopes to understand the ocean carbon cycle and the ways ocean acidification can affect the marine environment and critical ecosystem services.
INTRODUCTION: THE LINK BETWEEN THE OCEANS AND CLIMATE
The global carbon cycle describes the fluxes of carbon between different environmental compartments (atmosphere, ocean, terrestrial biosphere and sediments). This carbon may be for example in the form of carbon dioxide (CO2) or methane (CH4), both prominent greenhouse gases. It is essential to quantify these changes and stocks of carbon accurately in order to construct the climate models used to predict the impacts of climate change.
At least one quarter of the CO2 released into the atmosphere by anthropogenic activities such as the burning of fossil fuels is taken up by the ocean. Some of this CO2 returns to the atmosphere, and some is exported from surface waters to the deep ocean, where the reservoir of carbon is 50 times larger than that stored in the atmosphere. The ocean provides a vital service to nature through this capacity to regulate atmospheric CO2 emissions.
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OCEAN ACIDIFICATION
The absorption of CO2 by the ocean is not without consequences for marine life. It causes ocean acidification: a change in oceanic carbonate chemistry sometimes referred to as the ‘other CO2 problem’. Ocean acidification has emerged as a key global issue in the last decade because of its potential to affect marine organisms and biogeochemical cycles.
Ocean acidification comprises a series of changes to seawater chemistry, such as a decrease in seawater pH level (a measure of acidity/alkalinity), reflecting a shift towards increased acidity. These changes are measurable: average ocean pH levels have decreased by 0.1 since the onset of the Industrial Revolution, which is equivalent to an increase in acidity of 26%. However it is hard to estimate the full impact that ocean acidification will have on marine life. Studies show a wide variety of possible impacts, both positive and negative, and different species show different levels of resilience and adaptability.
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UNDERSTANDING THE IMPACTS OF OCEAN ACIDIFICATION
Nuclear and isotopic techniques are powerful tools for studying ocean acidification and have contributed widely to investigating past changes in ocean acidity and potential impacts on marine organisms. For example, boron isotopes enable scientists to assess past ocean pH levels using corals and fossilized organisms and identify past ‘acidification events’, with possible correlations with mass extinctions and changes in ecosystem structure.
Because of the potential impacts of ocean acidification on marine environments and ecosystems, the IAEA Environment Laboratories conduct research and support Member States in gaining a better understanding of areas such as the economic implications of ocean acidification for fisheries.
In addition to conducting research, the IAEA laboratories in Monaco host the Ocean Acidification International Coordination Centre (OA-ICC) which fosters global scientific collaboration to support fact-based understanding of the potential impacts of
ocean acidification on the marine environment and coastal populations. The Monaco laboratories also build awareness of the ways in which conventional, nuclear and isotopic techniques can be used to understand the effect of changes in seawater chemistry, marine organisms and ecosystems, coupled with other human pressures like overfishing, eutrophication and pollution.
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IAEA, 12 November 2021. Full report.
