Recent acceleration of the sea surface f CO 2 growth rate in the North Atlantic subpolar gyre (1993-2008) revealed by winter observations

• Published in: Global Biogeochemical Cycles
• Main Authors: Metzl, Nicolas, Corbière, Antoine, Reverdin, Gilles, Lenton, Andrew, Takahashi, Taro, Olsen, Are, Johannessen, Truls, Pierrot, Denis, Wanninkhof, Rik H., Ólafsdóttir, Sólveig R., Olafsson, Jon, Ramonet, Michel
• Other Authors: Laboratoire d'Océanographie et du Climat : Expérimentations et Approches Numériques (LOCEAN), Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales Toulouse (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales Toulouse (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Lamont-Doherty Earth Observatory (LDEO), Columbia University New York, Bjerknes Centre for Climate Research (BCCR), Department of Biological Sciences Bergen (BIO / UiB), University of Bergen (UiB)-University of Bergen (UiB), Cooperative Institute for Marine and Atmospheric Studies (CIMAS), Rosenstiel School of Marine and Atmospheric Science (RSMAS), University of Miami Coral Gables -University of Miami Coral Gables, NOAA Atlantic Oceanographic and Meteorological Laboratory (AOML), National Oceanic and Atmospheric Administration (NOAA), Marine and Freshwater Research Institute, Institute of Earth Sciences Reykjavik, University of Iceland Reykjavik, ICOS-RAMCES (ICOS-RAMCES), Laboratoire des Sciences du Climat et de l'Environnement Gif-sur-Yvette (LSCE), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2010
• Subjects: Oceanography: Biological and Chemical: Carbon cycling (0428); Oceanography: General: Climate and interannual variability (1616 1635 3305 3309 4513); Global Change: Biogeochemical cycles processes and modeling (0412 0141 0793 4805 4912); [PHYS.PHYS.PHYS-GEO-PH]Physics [physics]/Physics [physics]/Geophysics [physics.geo-ph]; [SDU.STU.GP]Sciences of the Universe [physics]/Earth Sciences/Geophysics [physics.geo-ph]; Canada; Irminger Basin; Iceland; North Atlantic; North Atlantic oscillation
• Online Access: https://hal.science/hal-00758935; https://hal.science/hal-00758935/document; https://hal.science/hal-00758935/file/2009GB003658%281%29.pdf; https://doi.org/10.1029/2009GB003658

International audience Recent studies based on ocean and atmospheric carbon dioxide (CO 2 ) observations, suggesting that the ocean carbon uptake has been reduced, may help explain the increase in the fraction of anthropogenic CO 2 emissions that remain in the atmosphere. Is it a response to climate change or a signal of ocean natural variability or both? Regional process analyses are needed to follow the ocean carbon uptake and to enable better attributions of the observed changes. Here, we describe the evolution of the surface ocean CO 2 fugacity ( f CO 2 oc ) over the period 1993-2008 in the North Atlantic subpolar gyre (NASPG). This analysis is based primarily on observations of dissolved inorganic carbon (DIC) and total alkalinity (TA) conducted at different seasons in the NASPG between Iceland and Canada. The f CO 2 oc trends based on DIC and TA data are also compared with direct f CO 2 measurements obtained between 2003 and 2007 in the same region. During winters 1993-2003, the f CO 2 oc growth rate was 3.7 (±0.6) μatm yr -1 , higher than in the atmosphere, 1.8 (±0.1) μatm yr -1 . This translates to a reduction of the ocean carbon uptake primarily explained by sea surface warming, up to 0.24 (±0.04) °C yr -1 . This warming is a consequence of advection of warm water northward from the North Atlantic into the Irminger basin, which occurred as the North Atlantic Oscillation (NAO) index moved into a negative phase in winter 1995/1996. In winter 2001-2008, the f CO 2 oc rise was particularly fast, between 5.8 (±1.1) and 7.2 (±1.3) μatm yr -1 depending on the region, more than twice the atmospheric growth rate of 2.1 (±0.2) μatm yr -1 , and in the winter of 2007-2008 the area was supersaturated with CO 2 . As opposed to the 1990s, this appears to be almost entirely due to changes in seawater carbonate chemistry, the combination of increasing DIC and decreasing of TA. The rapid f CO 2 oc increase was not only driven by regional uptake of anthropogenic CO 2 but was also likely controlled by a recent increase ...