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Earth System Dynamics An interactive open-access journal of the European Geosciences Union
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Volume 9, issue 2 | Copyright
Earth Syst. Dynam., 9, 339-357, 2018
https://doi.org/10.5194/esd-9-339-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 06 Apr 2018

Research article | 06 Apr 2018

Assessing carbon dioxide removal through global and regional ocean alkalinization under high and low emission pathways

Andrew Lenton1,2, Richard J. Matear1, David P. Keller3, Vivian Scott4, and Naomi E. Vaughan5 Andrew Lenton et al.
  • 1CSIRO Oceans and Atmosphere, Hobart, Australia
  • 2Antarctic Climate and Ecosystems Co-operative Research Centre, Hobart, Australia
  • 3GEOMAR Helmholtz Centre for Ocean Research, Kiel, Germany
  • 4School of Geosciences, University of Edinburgh, Edinburgh, UK
  • 5Tyndall Centre for Climate Change Research, School of Environmental Sciences, University of East Anglia, Norwich, UK

Abstract. Atmospheric carbon dioxide (CO2) levels continue to rise, increasing the risk of severe impacts on the Earth system, and on the ecosystem services that it provides. Artificial ocean alkalinization (AOA) is capable of reducing atmospheric CO2 concentrations and surface warming and addressing ocean acidification. Here, we simulate global and regional responses to alkalinity (ALK) addition (0.25PmolALKyr−1) over the period 2020–2100 using the CSIRO-Mk3L-COAL Earth System Model, under high (Representative Concentration Pathway 8.5; RCP8.5) and low (RCP2.6) emissions. While regionally there are large changes in alkalinity associated with locations of AOA, globally we see only a very weak dependence on where and when AOA is applied. On a global scale, while we see that under RCP2.6 the carbon uptake associated with AOA is only ∼ 60% of the total, under RCP8.5 the relative changes in temperature are larger, as are the changes in pH (140%) and aragonite saturation state (170%). The simulations reveal AOA is more effective under lower emissions, therefore the higher the emissions the more AOA is required to achieve the same reduction in global warming and ocean acidification. Finally, our simulated AOA for 2020–2100 in the RCP2.6 scenario is capable of offsetting warming and ameliorating ocean acidification increases at the global scale, but with highly variable regional responses.

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Artificial ocean alkalinization (AOA) is capable of reducing atmospheric carbon dioxide concentrations and surface warming while also addressing ocean acidification. We simulate the Earth system response to a fixed addition of AOA under low and high emissions. We explore the regional and global response to AOA. A key finding is that AOA is much more effective at reducing warming and ocean acidification under low emissions, despite lower carbon uptake.
Artificial ocean alkalinization (AOA) is capable of reducing atmospheric carbon dioxide...
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