Long-term trends in surface ocean pH in the North Atlantic

Author(s) Lauvset, S.K., Gruber, N.
Publication Type Journal Items, Publication Status: Published
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Title Long-term trends in surface ocean pH in the North Atlantic
Author(s) Lauvset, S.K.
Gruber, N.
Journal or Series Title Marine chemistry
Volume Number 162
Start Page 71
End Page 76
ISSN 0304-4203
1872-7581
Publisher Elsevier
Publication Place Amsterdam
Publication Date 2014
Keyword(s) pH
Ocean acidification
Trend analysis
Carbon cycle
North Atlantic
Abstract Presently available direct pH measurements do not have a sufficient data density in space or time in order to determine long-term trends across wider geographic regions, limiting our ability to assess the magnitude and impacts of ocean acidification. We overcome this limitation by using the much more frequently measured fugacity of CO2 (fCO(2)), as synthesized in the SOCAT data product, from which we calculate pH using algorithms for alkalinity based on temperature and salinity. The estimated pH at 25 degrees C, i.e., pH(sws)(25 degrees C) has a calculation error of 0.0033 +/- 0.0003, and evaluation using co-located pH observations yields a RMSE of 0.010 and a non-significant bias of 0.004. The estimated pH(sws)(25 degrees C) is rather sensitive to uncertainties and biases in fCO(2), while uncertainties in alkalinity, temperature, and salinity matter much less. The high precision and low bias of the computed pH permit us to apply this method to data from the North Atlantic Subpolar Gyre, for which we find a statistically significant trend in surface ocean pH(sws)(insitu) of -0.0022 +/- 0.0004 yr(-1) over the period 1981 to 2007. This long-term trend in pH is nearly entirely driven by the long-term trend in surface ocean fCO(2), while the impact of temperature is negligible. This pH trend is very close to that expected based on the assumption of thermodynamic equilibrium of CO2 between the atmosphere and the surface ocean.
DOI 10.1016/j.marchem.2014.03.009
Additional Notes Received 30 January 2014, Received in revised form 17 March 2014, Accepted 18 March 2014, Available online 27 March 2014
Document Type Article
Publication Status Published
Language English
Assigned Organisational Unit(s) 03731
Organisational Unit(s)
NEBIS System Number 000015960
Source Database ID WOS-000337012700008
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@article{Lvst2014,
author = "Lauvset, S.K. and Gruber, N.",
title = "{L}ong-term trends in surface ocean p{H} in the {N}orth {A}tlantic",
journal = "Marine chemistry",
year = 2014,
volume = "162",
pages = "71--76",
}


E-Citations record created: Mon, 07 Jul 2014, 08:07:37 CET