Journal cover Journal topic
Biogeosciences An interactive open-access journal of the European Geosciences Union
Journal topic
Volume 15, issue 14
Biogeosciences, 15, 4661-4682, 2018
https://doi.org/10.5194/bg-15-4661-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 3.0 License.

Special issue: Progress in quantifying ocean biogeochemistry – in honour...

Biogeosciences, 15, 4661-4682, 2018
https://doi.org/10.5194/bg-15-4661-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 30 Jul 2018

Research article | 30 Jul 2018

Transport and storage of anthropogenic C in the North Atlantic Subpolar Ocean

Virginie Racapé1,2, Patricia Zunino3, Herlé Mercier3, Pascale Lherminier2, Laurent Bopp1,4, Fiz F. Pérèz5, and Marion Gehlen1 Virginie Racapé et al.
  • 1LSCE/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, France
  • 5Instituto de Investigaciones Marinas, CSIC, Eduardo Cabello 6, 36208 Vigo, Spain

Abstract. The North Atlantic Ocean is a major sink region for atmospheric CO2 and contributes to the storage of anthropogenic carbon (Cant). While there is general agreement 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 evolution over the 21st century remain uncertain. This study investigates the relationship between transport, air–sea flux and storage rate of Cant in the North Atlantic Subpolar Ocean over the past 53 years. Its relies on the combined analysis of a multiannual in situ data set and outputs from a global biogeochemical ocean general circulation model (NEMO–PISCES) at 1∕2° spatial resolution forced by an atmospheric reanalysis. Despite an underestimation of Cant transport and an overestimation of anthropogenic air–sea CO2 flux in the model, the interannual variability of the regional Cant storage rate and its driving processes were well simulated by the model. Analysis of the multi-decadal simulation revealed that the MOC intensity variability was the major driver of the Cant transport variability at 25 and 36°N, but not at OVIDE. At the subpolar OVIDE section, the interannual variability of Cant transport was controlled by the accumulation of Cant in the MOC upper limb. At multi-decadal timescales, long-term changes in the North Atlantic storage rate of Cant were driven by the increase in air–sea fluxes of anthropogenic CO2. North Atlantic Central Water played a key role for storing Cant in the upper layer of the subtropical region and for supplying Cant to Intermediate Water and North Atlantic Deep Water. The transfer of Cant from surface to deep waters occurred mainly north of the OVIDE section. Most of the Cant transferred to the deep ocean was stored in the subpolar region, while the remainder was exported to the subtropical gyre within the lower MOC.

Publications Copernicus
Special issue
Download
Short summary
This study of a model–data comparison investigates the relationship between transport, air–sea flux and storage rate of Cant in the North Atlantic Subpolar Ocean over the past 53 years. It reveals the key role played by Central Water for storing Cant in the subtropical region and for supplying Cant into the deep ocean. The Cant transfer to the deep ocean occurred mainly north of the OVIDE section, and just a small fraction was exported to the subtropical gyre within the lower MOC.
This study of a model–data comparison investigates the relationship between transport, air–sea...
Citation
Share