Impact of enhanced vertical mixing on marine biogeochemistry: lessons for geo-engineering and natural variability

• Published in: Biogeosciences
• Main Authors: Dutreuil, Sébastien, Bopp, L, Tagliabue, A
• Other Authors: Laboratoire de géologie de l'ENS (LGENS), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Département des Géosciences - ENS Paris, École normale supérieure - Paris (ENS-PSL), Université Paris Sciences et Lettres (PSL)-Université Paris Sciences et Lettres (PSL)-École normale supérieure - Paris (ENS-PSL), Université Paris Sciences et Lettres (PSL)-Université Paris Sciences et Lettres (PSL), Laboratoire des Sciences du Climat et de l'Environnement Gif-sur-Yvette (LSCE), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Department of Earth Ocean and Ecological Sciences Liverpool, University of Liverpool
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2009
• Subjects: geoengineering; ocean pipes; [SDE.IE]Environmental Sciences/Environmental Engineering; [SDU.OCEAN]Sciences of the Universe [physics]/Ocean; Atmosphere; Alka; Southern Ocean
• Online Access: https://hal.science/hal-01109181; https://hal.science/hal-01109181/document; https://hal.science/hal-01109181/file/Dutreuil%20Bopp%20Tagliabue%20-%20Biogeosciences%2009%20-%20impact.pdf; https://doi.org/10.5194/bg-6-901-2009

International audience Artificially enhanced vertical mixing has been suggested as a means by which to fertilize the biological pump with subsurface nutrients and thus increase the oceanic CO 2 sink. We use an ocean general circulation and biogeo-chemistry model (OGCBM) to examine the impact of arti-ficially enhanced vertical mixing on biological productivity and atmospheric CO 2 , as well as the climatically significant gases nitrous oxide (N 2 O) and dimethyl sulphide (DMS) dur-ing simulations between 2000 and 2020. Overall, we find a large increase in the amount of organic carbon exported from surface waters, but an overall increase in atmospheric CO 2 concentrations by 2020. We quantified the individual effect of changes in dissolved inorganic carbon (DIC), alka-linity and biological production on the change in pCO 2 at characteristic sites and found the increased vertical supply of carbon rich subsurface water to be primarily responsible for the enhanced CO 2 outgassing, although increased alkalinity and, to a lesser degree, biological production can compensate in some regions. While ocean-atmosphere fluxes of DMS do increase slightly, which might reduce radiative forcing, the oceanic N 2 O source also expands. Our study has impli-cations for understanding how natural variability in vertical mixing in different ocean regions (such as that observed re-cently in the Southern Ocean) can impact the ocean CO 2 sink via changes in DIC, alkalinity and carbon export.