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

Type Article
Date 2018-07
Language English
Author(s) Racape Virginie1, 2, Zunino PatriciaORCID3, Mercier HerleORCID3, Lherminier PascaleORCID2, Bopp Laurent1, 4, Perez Fiz F5, Gehlen Marion1
Affiliation(s) 1 : CEA CNRS UVSQ, CEA Saclay, LSCE, IPSL, Bat 712, F-91190 Gif Sur Yvette, France.
2 : IFREMER, CNRS IFREMER IRD UBO, Lab Oceanog Phys & Spatiale, UMR 6523, Plouzane, France
3 : CNRS IFREMER IRD UBO, Lab Oceanog Phys & Spatiale, CNRS, UMR 6523, Plouzane, France.
4 : Ecole Normale Super, Dept Geosci, 24 Rue Lhomond, F-75005 Paris, France.
5 : CSIC, Inst Invest Marinas, Eduardo Cabello 6, Vigo 36208, Spain.
Source Biogeosciences (1726-4170) (Copernicus Gesellschaft Mbh), 2018-07 , Vol. 15 , N. 14 , P. 4661-4682
DOI 10.5194/bg-15-4661-2018
WOS© Times Cited 5
Note Special issue Progress in quantifying ocean biogeochemistry – in honour of Ernst Maier-Reimer Editor(s): C. Heinze, T. Ilyina, A. Winguth, J. Segschneider, and M. Hofmann

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 degrees 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 degrees 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.

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