Global warming driven by the emission of greenhouse gases is threatening all sectors of human society. In addition to reduction of carbon dioxide (CO₂) emissions, accelerated CO₂ removal (CDR) is also needed to limit global warming to 2^oC above the pre-industrial level. The ocean is the largest active carbon pool, and it has a huge potential for removing atmospheric CO₂. Here we report the effects of aluminum (Al) on marine carbon sinks and the possibility of Al fertilization as an ocean-based CDR. Our laboratory and field studies show that Al addition generally enhances carbon fixation by marine phytoplankton such as marine diatoms and nitrogen-fixing cyanobacteria, etc., by facilitating the use of dissolved organic phosphorus, iron (Fe), and dinitrogen. Moreover, Al may preserve organic carbon from decay and would facilitate the export of the fixed carbon to ocean depths and its sequestration there. We estimate that addition of Al at oceanic relevant levels would lead to 1 to 3 orders of magnitude increases in diatom POC exported to 1000 m in depth. In addition, increases of Al in the range from 20 to 200 nM in the upper ocean might have occurred due to the high dust deposition over the world ocean in glacial times. The Antarctic ice core records show that the emergence of glacial climates was closely linked to high input of dust Al and Fe over the past 800,000 years. Therefore, we built on the Iron Hypothesis to propose the Iron-Aluminum Hypothesis to highlight the importance of Al in carbon fixation, export, and sequestration in the ocean, and thus climate change. Overall, we propose that ocean Al fertilization could be a potential CDR strategy used alone or together with other CDRs such as ocean Fe fertilization, artificial upwelling, and alkalinity enhancement to alleviate global warming.

Primary Presenter: Linbin Zhou, South China Sea Institute of Oceanology, Chinese Academy of Sciences (zhoulb@scsio.ac.cn)

Authors:

Linbin Zhou, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, China  (zhoulb@scsio.ac.cn)

Fengjie Liu, School of Environmental Sciences, University of Liverpool, Liverpool, United Kingdom  (fengjieliu2012@gmail.com)

Yehui Tan, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, China  (tanyh@scsio.ac.cn)

Claude Fortin, Institut national de la recherche scientifique, Centre Eau Terre Environnement, Québec, Canada  (claude.fortin@ete.inrs.ca)

Liangmin Huang, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, China  (hlm@scsio.ac.cn)

Peter Campbell, Institut national de la recherche scientifique, Centre Eau Terre Environnement, Québec, Canada  (peter.campbell@inrs.ca)

Martha Gledhill, GEOMAR Helmholtz Centre for Ocean Research, Kiel, Germany  (mgledhill@geomar.de)

Eric Achterberg,  GEOMAR Helmholtz Centre for Ocean Research, Kiel, Germany  (eachterberg@geomar.de)