@article{f0f730affc4d40f58e03f811c566ba3a,
title = "Testing the climate intervention potential of ocean afforestation using the Great Atlantic Sargassum Belt",
abstract = "Ensuring that global warming remains <2 °C requires rapid CO 2 emissions reduction. Additionally, 100–900 gigatons CO 2 must be removed from the atmosphere by 2100 using a portfolio of CO 2 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 CO 2 influx into the surface seawater, after CO 2-fixation by Sargassum, takes 2.5–18 times longer than the CO 2-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. ",
keywords = "Carbon cycle, Marine biology, Ocean sciences",
author = "Bach, {Lennart T.} and Veronica Tamsitt and Jim Gower and Hurd, {Catriona L.} and Raven, {John A.} and Boyd, {Philip W.}",
note = "Funding Information: We thank Chuanmin Hu and Mengqiu Wang for providing their monthly composites of gridded Sargassum biomass data; Daniel Jones, Takamitsu Ito, Yohei Takano, and Wei-Ching Hsu for providing model output data on surface water residence time; Martin Jung and Jens Daniel M{\"u}ller for their photographs of Sargassum rafts; Andrew Lenton for proof-reading the manuscript. This study was funded by the Australian Research Council by a Laureate awarded to P.W.B. (FL160100131). V.T. acknowledges support from CSHOR, a joint research Centre for Southern Hemisphere Ocean Research between QNLM and CSIRO. Argo data were collected and made freely available by the International Argo Program and the national programs that contribute to it (http://www.argo. ucsd.edu; http://argo.jcommops.org; https://doi.org/10.17882/42182). The Argo Program is part of the Global Ocean Observing System. The ERA5 dataset used for biomass and equilibration timescale estimations was developed by the European Centre for Medium-Range Weather Forecasts and was obtained from the Research Data Archive at the National Center for Atmospheric Research, Computational and Information Systems Laboratory. Analyses and visualizations used for albedo calculations were partially produced with the Giovanni online data system, developed and maintained by the NASA GES DISC. We acknowledge the mission scientists and Principal Investigators who provided the data used in the albedo calcuations. Publisher Copyright: {\textcopyright} 2021, The Author(s).",
year = "2021",
month = may,
day = "7",
doi = "10.1038/s41467-021-22837-2",
language = "English",
volume = "12",
journal = "Nature Communications",
issn = "2041-1723",
publisher = "Nature Publishing Group",
}
