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 ope...
Published in: | Nature Communications |
---|---|
Main Authors: | , , , , , |
Format: | Article in Journal/Newspaper |
Language: | English |
Published: |
Springer Science and Business Media LLC
2021
|
Subjects: | |
Online Access: | http://dx.doi.org/10.1038/s41467-021-22837-2 http://www.nature.com/articles/s41467-021-22837-2.pdf http://www.nature.com/articles/s41467-021-22837-2 |
Summary: | 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. |
---|