Coastal ocean acidification and increasing total alkalinity in the northwestern Mediterranean Sea

Abstract : Coastal time series of ocean carbonate chemistry are critical for understanding how global anthropogenic change manifests in near-shore ecosystems. Yet, they are few and have low temporal resolution. At the time series station Point B in the northwestern Mediterranean Sea, seawater was sampled weekly from 2007 through 2015, at 1 and 50 m, and analyzed for total dissolved inorganic carbon (C T) and total alkalinity (A T). Parameters of the carbonate system such as pH (pH T , total hydrogen ion scale) were calculated and a deconvolution analysis was performed to identify drivers of change. The rate of surface ocean acidification was −0.0028 ± 0.0003 units pH T yr −1. This rate is larger than previously identified open-ocean trends due to rapid warming that occurred over the study period (0.072 ± 0.022 • C yr −1). The total pH T change over the study period was of similar magnitude as the diel pH T variability at this site. The acidification trend can be attributed to atmospheric carbon dioxide (CO 2) forcing (59 %, 2.08 ± 0.01 ppm CO 2 yr −1) and warming (41 %). Similar trends were observed at 50 m but rates were generally slower. At 1 m depth, the increase in atmospheric CO 2 accounted for approximately 40 % of the observed increase in C T (2.97 ± 0.20 µmol kg −1 yr −1). The remaining increase in C T may have been driven by the same unidentified process that caused an increase in A T (2.08 ± 0.19 µmol kg −1 yr −1). Based on the analysis of monthly trends, synchronous increases in C T and A T were fastest in the spring–summer transition. The driving process of the interannual increase in A T has a seasonal and shallow component, which may indicate riverine or groundwater influence. This study exemplifies the importance of understanding changes in coastal carbonate chemistry through the lens of biogeochemical cycling at the land–sea interface. This is the first coastal acidification time series providing multi-year data at high temporal resolution. The data confirm rapid warming in the Mediterranean Sea and demonstrate coastal acidification with a synchronous increase in total alkalinity.
Type de document :
Article dans une revue
Ocean Science, European Geosciences Union, 2017, 13 (3), pp.411-426. 〈10.5194/os-13-411-2017〉
Liste complète des métadonnées

Littérature citée [76 références]  Voir  Masquer  Télécharger
Contributeur : Gestionnaire Hal-Upmc <>
Soumis le : mercredi 7 juin 2017 - 16:42:41
Dernière modification le : mardi 29 mai 2018 - 12:50:39
Document(s) archivé(s) le : vendredi 8 septembre 2017 - 13:15:38


Publication financée par une institution


Distributed under a Creative Commons Paternité 4.0 International License




Lydia Kapsenberg, Samir Alliouane, Frédéric Gazeau, Laure Mousseau, Jean-Pierre Gattuso. Coastal ocean acidification and increasing total alkalinity in the northwestern Mediterranean Sea. Ocean Science, European Geosciences Union, 2017, 13 (3), pp.411-426. 〈10.5194/os-13-411-2017〉. 〈hal-01534516〉



Consultations de la notice


Téléchargements de fichiers