Increase of dissolved inorganic carbon and decrease in pH in near-surface waters in the Mediterranean Sea during the past two decades

Type Article
Date 2018-09
Language English
Author(s) Merlivat Liliane1, Boutin Jacqueline1, Antoine DavidORCID2, 3, Beaumont Laurence4, Golbol Melek3, Vellucci Vincenzo3
Affiliation(s) 1 : Sorbonne Univ, CNRS, IRD, MNHN,LOCEAN, F-75005 Paris, France.
2 : Curtin Univ, Sch Earth & Planetary Sci, Remote Sensing & Satellite Res Grp, Perth, WA, Australia.
3 : Sorbonne Univ, CNRS, LOV, F-06230 Villefranche Sur Mer, France.
4 : INSU CNRS, Div Tech, F-92195 Meudon, France.
Source Biogeosciences (1726-4170) (Copernicus Gesellschaft Mbh), 2018-09 , Vol. 15 , N. 18 , P. 5653-5662
DOI 10.5194/bg-15-5653-2018
WOS© Times Cited 7
Abstract

Two 3-year time series of hourly measurements of the fugacity of CO2 (f CO2) in the upper 10 m of the surface layer of the northwestern Mediterranean Sea have been recorded by CARIOCA sensors almost two decades apart, in 1995-1997 and 2013-2015. By combining them with the alkalinity derived from measured temperature and salinity, we calculate changes in pH and dissolved inorganic carbon (DIC). DIC increased in surface seawater by similar to 25 mu mol kg(-1) and fCO(2) by 40 mu atm, whereas seawater pH decreased by similar to 0.04 (0.0022 yr(-1)). The DIC increase is about 15 % larger than expected from the equilibrium with atmospheric CO2. This could result from natural variability, e.g. the increase between the two periods in the frequency and intensity of winter convection events. Likewise, it could be the signature of the contribution of the Atlantic Ocean as a source of anthropogenic carbon to the Mediterranean Sea through the Strait of Gibraltar. We then estimate that the part of DIC accumulated over the last 18 years represents similar to 30 % of the total inventory of anthropogenic carbon in the Mediterranean Sea.

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Merlivat Liliane, Boutin Jacqueline, Antoine David, Beaumont Laurence, Golbol Melek, Vellucci Vincenzo (2018). Increase of dissolved inorganic carbon and decrease in pH in near-surface waters in the Mediterranean Sea during the past two decades. Biogeosciences, 15(18), 5653-5662. Publisher's official version : https://doi.org/10.5194/bg-15-5653-2018 , Open Access version : https://archimer.ifremer.fr/doc/00585/69695/