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

Bach, LT; Tamsitt, V; Gower, J; Hurd, CL; Raven, JA; Boyd, PW

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

Bach, LT Tamsitt, V Gower, J Hurd, CL Raven, JA Boyd, PW

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Publisher:: Nature Research
Publication Type:: Journal Article
Citation:: Nature Communications, 2021, 12, (1), pp. 1-10
Issue Date:: 2021-05-07

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Field	Value	Language
dc.contributor.author	Bach, LT
dc.contributor.author	Tamsitt, V
dc.contributor.author	Gower, J
dc.contributor.author	Hurd, CL
dc.contributor.author	Raven, JA
dc.contributor.author	Boyd, PW
dc.date.accessioned	2022-02-14T02:44:18Z
dc.date.available	2021-03-29
dc.date.available	2022-02-14T02:44:18Z
dc.date.issued	2021-05-07
dc.identifier.citation	Nature Communications, 2021, 12, (1), pp. 1-10
dc.identifier.issn	2041-1723
dc.identifier.issn	2041-1723
dc.identifier.uri	http://hdl.handle.net/10453/154484
dc.description.abstract	Ensuring that global warming remains <2 °C requires rapid CO2 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.
dc.format	Electronic
dc.language	eng
dc.publisher	Nature Research
dc.relation.ispartof	Nature Communications
dc.relation.isbasedon	10.1038/s41467-021-22837-2
dc.rights	info:eu-repo/semantics/openAccess
dc.subject.mesh	Atlantic Ocean
dc.subject.mesh	Atmosphere
dc.subject.mesh	Biomass
dc.subject.mesh	Calcium
dc.subject.mesh	Carbon Dioxide
dc.subject.mesh	Ecosystem
dc.subject.mesh	Feedback
dc.subject.mesh	Global Warming
dc.subject.mesh	Hydrogen-Ion Concentration
dc.subject.mesh	Sargassum
dc.subject.mesh	Seawater
dc.subject.mesh	Temperature
dc.subject.mesh	Time Factors
dc.subject.mesh	Tropical Climate
dc.subject.mesh	Sargassum
dc.subject.mesh	Carbon Dioxide
dc.subject.mesh	Calcium
dc.subject.mesh	Ecosystem
dc.subject.mesh	Biomass
dc.subject.mesh	Temperature
dc.subject.mesh	Atmosphere
dc.subject.mesh	Tropical Climate
dc.subject.mesh	Seawater
dc.subject.mesh	Hydrogen-Ion Concentration
dc.subject.mesh	Time Factors
dc.subject.mesh	Feedback
dc.subject.mesh	Atlantic Ocean
dc.subject.mesh	Global Warming
dc.title	Testing the climate intervention potential of ocean afforestation using the Great Atlantic Sargassum Belt
dc.type	Journal Article
utslib.citation.volume	12
utslib.location.activity	England
pubs.organisational-group	/University of Technology Sydney
pubs.organisational-group	/University of Technology Sydney/Faculty of Science
utslib.copyright.status	open_access	*
pubs.consider-herdc	false
dc.date.updated	2022-02-14T02:44:14Z
pubs.issue	1
pubs.publication-status	Published
pubs.volume	12
utslib.citation.issue	1

Abstract:

Ensuring that global warming remains <2 °C requires rapid CO2 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.

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http://hdl.handle.net/10453/154484