Surface ocean carbon dioxide during the Atlantic Meridional Transect (1995–2013); evidence of ocean acidification

Kitidis, V, Brown, IJ, Hardman-Mountford, NJ and Lefèvre, N 2017 Surface ocean carbon dioxide during the Atlantic Meridional Transect (1995–2013); evidence of ocean acidification. Progress in Oceanography, 158. 65-75.

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Here we present more than 21,000 observations of carbon dioxide fugacity in air and seawater (fCO2) along the Atlantic Meridional Transect (AMT) programme for the period 1995–2013. Our dataset consists of 11 southbound and 2 northbound cruises in boreal autumn and spring respectively. Our paper is primarily focused on change in the surface-ocean carbonate system during southbound cruises. We used observed fCO2 and total alkalinity (TA), derived from salinity and temperature, to estimate dissolved inorganic carbon (DIC) and pH (total scale). Using this approach, estimated pH was consistent with spectrophotometric measurements carried out on 3 of our cruises. The AMT cruises transect a range of biogeographic provinces where surface Chlorophyll-a spans two orders of magnitude (mesotrophic high latitudes to oligotrophic subtropical gyres). We found that surface Chlorophyll-a was negatively correlated with fCO2, but that the deep chlorophyll maximum was not a controlling variable for fCO2. Our data show clear evidence of ocean acidification across 100� of latitude in the Atlantic Ocean. Over the period 1995–2013 we estimated annual rates of change in: (a) sea surface temperature of 0.01 ± 0.05 �C, (b) seawater fCO2 of 1.44 ± 0.84 latm, (c) DIC of 0.87 ± 1.02 lmol per kg and (d) pH of �0.0013 ± 0.0009 units. Monte Carlo simulations propagating the respective analytical uncertainties showed that the latter were < 5% of the observed trends. Seawater fCO2 increased at the same rate as atmospheric CO2.

Item Type: Publication - Article
Subjects: Atmospheric Sciences
Earth Sciences
Marine Sciences
Divisions: Plymouth Marine Laboratory > Science Areas > Marine Biochemistry and Observations
Depositing User: Vassilis Kitidis
Date made live: 26 Apr 2018 07:46
Last Modified: 25 Apr 2020 09:58

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