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Testing the climate intervention potential of ocean afforestation using the Great Atlantic Sargassum Belt


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Bach, LT ORCID: 0000-0003-0202-3671, Tamsitt, V, Gower, J, Hurd, CL ORCID: 0000-0001-9965-4917, Raven, JA and Boyd, PW ORCID: 0000-0001-7850-1911 2021 , 'Testing the climate intervention potential of ocean afforestation using the Great Atlantic Sargassum Belt' , Nature Communications, vol. 12, no. 1 , pp. 1-10 , doi: 10.1038/s41467-021-22837-2.

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Ensuring that global warming remains 2 emissions reduction. Additionally, 100–900 gigatons CO2 must be removed from the atmosphere by 2100 using a portfolio of CO2 removal (CDR) methods. Ocean afforestation, CDR through basin-scale seaweed farming in the open ocean, is seen as a key component of the marine portfolio. Here, we analyse the CDR potential of recent re-occurring trans-basin belts of the floating seaweed Sargassum in the (sub)tropical North Atlantic as a natural analogue for ocean afforestation. We show that two biogeochemical feedbacks, nutrient reallocation and calcification by encrusting marine life, reduce the CDR efficacy of Sargassum by 20–100%. Atmospheric CO2 influx into the surface seawater, after CO2-fixation by Sargassum, takes 2.5–18 times longer than the CO2-deficient seawater remains in contact with the atmosphere, potentially hindering CDR verification. Furthermore, we estimate that increased ocean albedo, due to floating Sargassum, could influence climate radiative forcing more than Sargassum-CDR. Our analysis shows that multifaceted Earth-system feedbacks determine the efficacy of ocean afforestation.

Item Type: Article
Authors/Creators:Bach, LT and Tamsitt, V and Gower, J and Hurd, CL and Raven, JA and Boyd, PW
Keywords: ocean afforestation, seaweed farming, climate intervention, albedo
Journal or Publication Title: Nature Communications
Publisher: Nature Publishing Group
ISSN: 2041-1723
DOI / ID Number: 10.1038/s41467-021-22837-2
Copyright Information:

© The Author(s) 2021. This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.

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