Attributing seasonal pH variability in surface ocean waters to governing factors

On‐going ocean acidification and increasing availability of high‐frequency pH data have stimulated interest to understand seasonal pH dynamics in surface waters. Here we show that it is possible to accurately reproduce observed pH values by combining seasonal changes in temperature (T), dissolved in...

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Bibliographic Details
Published in:Geophysical research letters 2016-12, Vol.43 (24), p.12,528-12,537
Main Authors: Hagens, M., Middelburg, J. J.
Format: Article
Language:English
Subjects:
Acidification
Alkalinity
Annual variations
Availability
Carbon
carbon dioxide
Dissolved inorganic carbon
driving factors
Dynamical systems
Dynamics
Geochemistry
Inorganic carbon
Latitude
Ocean acidification
Oceans
Seasonal variation
Seasonal variations
Seasonality
Sensitivity
Stations
Summer
Surface water
Temperature
Temperature (air-sea)
Temperature effects
Time series
Variability
Winter
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Summary:On‐going ocean acidification and increasing availability of high‐frequency pH data have stimulated interest to understand seasonal pH dynamics in surface waters. Here we show that it is possible to accurately reproduce observed pH values by combining seasonal changes in temperature (T), dissolved inorganic carbon (DIC), and total alkalinity (TA) from three time series stations with novel pH sensitivity factors. Moreover, we quantify the separate contributions of T, DIC, and TA changes to winter‐to‐summertime differences in pH, which are in the ranges of −0.0334 to −0.1237, 0.0178 to 0.1169, and −0.0063 to 0.0234, respectively. The effects of DIC and temperature are therefore largely compensatory, and are slightly tempered by changes in TA. Whereas temperature principally drives pH seasonality in low‐latitude to midlatitude systems, winter‐to‐summer DIC changes are most important at high latitudes. This work highlights the potential of pH sensitivity factors as a tool for quantifying the driving mechanisms behind pH changes. Key Points The pH seasonality is reproduced using sensitivity factors and dissolved inorganic carbon (DIC), temperature, and alkalinity (TA) seasonalities Variations in DIC and temperature are the main drivers of pH seasonality and act in opposite directions, with a modulating role for TA Temperature and DIC are the principal drivers of pH variability at low to middle and high latitudes, respectively
ISSN:0094-8276
1944-8007
DOI:10.1002/2016GL071719