Transport and storage of anthropogenic C in the Subpolar North Atlantic:
Virginie Racapé1,2, Patricia Zunino3, Pascale Lherminier2, Herlé Mercier3, Laurent Bopp1,4, and Marion Gehlen11LSCE/IPSL, Laboratoire des Sciences du Climat et de l'environnement, CEA-CNRS-UVSQ, Orme des Merisiers, Bât. 712, CEA/Saclay, 91190 Gif-sur-Yvette, Cedex, France 2IFREMER, Laboratoire d'Océanographie Physique et Spatiale, UMR 6523, CNRS-IFREMER-IRD-UBO, Plouzané, France 3CNRS, Laboratoire d'Océanographie Physique et Spatiale, UMR 6523, CNRS-IFREMER-IRD-UBO, Plouzané, France 4Département de Géosciences, Ecole Normale Supérieure, 24 rue Lhomond 75005 Paris
Received: 12 Dec 2016 – Accepted for review: 20 Dec 2016 – Discussion started: 04 Jan 2017
Abstract. The North Atlantic Ocean is a major sink region for anthropogenic carbon (Cant) and a major contributor to its storage. While it is in general agreed that the intensity of the meridional overturning circulation (MOC) modulates uptake, transport and storage of Cant in the North Atlantic Subpolar Ocean, processes controlling their recent variability and 21st century evolution remain uncertain. This study aims to investigate the relationship between the transport of Cant across the Greenland-Portugal OVIDE section and the storage of Cant in the North Atlantic Subpolar Ocean over the past 44 years. Its relies on the combined analysis of a multi-annual data set (OVIDE program) and output from a global biogeochemical ocean general circulation model (NEMO/PISCES) at 1/2° spatial resolution forced by the atmospheric reanalysis Drakkar Forcing Set 4. The skill of the model to reproduce observed physical and biogeochemical characteristics, as well as their year-to-year variability is assessed over the period covered by observations. While the analysis of the 44 year long hindcast simulation reveals that the interannual variability of the storage rate of Cant is controlled by the northward transport during low NAO phases, as opposed to the air-sea flux during strong NAO phases, the progressive and continuous increase of the subpolar North Atlantic Cant inventory over the period 1958–2012 is driven by the regional uptake of Cant from the atmosphere. Our results suggest thus an increase of the Cant inventory in this region over the 21 st century assuming unabated emissions of CO2 and MOC fluctuation within observed boundaries.
Racapé, V., Zunino, P., Lherminier, P., Mercier, H., Bopp, L., and Gehlen, M.: Transport and storage of anthropogenic C in the Subpolar North Atlantic:
Model–Data comparison, Biogeosciences Discuss., doi:10.5194/bg-2016-541, in review, 2017.