title: European land CO2 sink influenced by NAO and East-Atlantic Pattern coupling.
abstract: Large-scale climate patterns control variability in the global carbon sink. In Europe, the North-Atlantic Oscillation (NAO) influences vegetation activity, however the East-Atlantic (EA) pattern is known to modulate NAO strength and location. Using observation-driven and modelled data sets, we show that multi-annual variability patterns of European Net Biome Productivity (NBP) are linked to anomalies in heat and water transport controlled by the NAO-EA interplay. Enhanced NBP occurs when NAO and EA are both in negative phase, associated with cool summers with wet soils which enhance photosynthesis. During anti-phase periods, NBP is reduced through distinct impacts of climate anomalies in photosynthesis and respiration. The predominance of anti-phase years in the early 2000s may explain the European-wide reduction of carbon uptake during this period, reported in previous studies. Results show that improving the capability of simulating atmospheric circulation patterns may better constrain regional carbon sink variability in coupled carbon-climate models.
authors.affiliation: Laboratoire des Sciences du Climat et de l'Environnement, LSCE/IPSL, CEA-CNRS-UVSQ, Université Paris-Saclay, F-91191 Gif-sur-Yvette, France.|Instituto Dom Luiz, IDL, Faculdade de Ciências, Universidade de Lisboa, Lisboa 1749-016, Portugal.
authors.forename: Ana
authors.identifier: http://orcid.org/0000-0002-7368-7806
authors.initials: A
authors.lastname: Bastos
authors.affiliation: Department of Biology, University of Antwerp, Universiteitsplein 1, 2610 Wilrijk, Belgium.
authors.forename: Ivan A
authors.initials: IA
authors.lastname: Janssens
authors.affiliation: Instituto Dom Luiz, IDL, Faculdade de Ciências, Universidade de Lisboa, Lisboa 1749-016, Portugal.
authors.forename: Célia M
authors.initials: CM
authors.lastname: Gouveia
authors.affiliation: Instituto Dom Luiz, IDL, Faculdade de Ciências, Universidade de Lisboa, Lisboa 1749-016, Portugal.
authors.forename: Ricardo M
authors.initials: RM
authors.lastname: Trigo
authors.affiliation: Laboratoire des Sciences du Climat et de l'Environnement, LSCE/IPSL, CEA-CNRS-UVSQ, Université Paris-Saclay, F-91191 Gif-sur-Yvette, France.
authors.forename: Philippe
authors.initials: P
authors.lastname: Ciais
authors.affiliation: Laboratoire des Sciences du Climat et de l'Environnement, LSCE/IPSL, CEA-CNRS-UVSQ, Université Paris-Saclay, F-91191 Gif-sur-Yvette, France.
authors.forename: Frédéric
authors.initials: F
authors.lastname: Chevallier
authors.affiliation: CREAF, Cerdanyola del Vallès, Catalonia, 08193 Barcelona, Spain.|CSIC, Global Ecology Unit CREAF-CSIC-UAB, Cerdanyola del Vallès, Catalonia, 08193 Barcelona, Spain.
authors.forename: Josep
authors.initials: J
authors.lastname: Peñuelas
authors.affiliation: Max Planck Institute for Biogeochemistry, Jena 07701, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Rödenbeck
authors.affiliation: Department of Ecology, College of Urban and Environmental Sciences, Peking University 5 Yiheyuan Road, Haidian District, Beijing 100871, China.
authors.forename: Shilong
authors.initials: S
authors.lastname: Piao
authors.affiliation: College of Engineering, Mathematics and Physical Sciences, University of Exeter, Exeter EX4 4QF, UK.
authors.forename: Pierre
authors.identifier: http://orcid.org/0000-0003-3309-4739
authors.initials: P
authors.lastname: Friedlingstein
authors.affiliation: Numerical Terradynamic Simulation Group, University of Montana, Missoula, Montana 59812, USA.
authors.forename: Steven W
authors.initials: SW
authors.lastname: Running