|Type||Normative document (norm, referencial, protocol)|
|Ref.||Argo data management|
|Author(s)||Johnson Kenneth S.1, Plant Joshua N., Maurer Tanya L.|
|Affiliation(s)||1 : Monterey Bay Aquarium Research Institute, Moss Landing, CA 95039|
Seawater proton concentration is a master variable that controls the air-sea gas exchange of CO2, the ability of organisms to produce calcium carbonate shells, and that tracks the production and respiration of organic carbon as CO2 is removed or added to water by biological processes. The proton concentration in seawater [H+] (mol kg-seawater-1) is typically reported as the pH = -log10 [H+]. The in situ proton concentration ranges from about 3 to 30 nmol kg-seawater-1 (7.5<pH<8.5).
Seawater pH is measured from profiling floats using a Deep-Sea DuraFET pH sensor that is manufactured at MBARI (Johnson et al., 2016) or at Sea-Bird Scientific (Float pH). The core of each sensor is an Ion Sensitive Field Effect Transistor (ISFET), produced by Honeywell, that responds to proton activity and a Ag/AgCl reference electrode that responds to chloride ion activity. When properly calibrated, the sensor measures the activity of HCl, which is the product of the activities of the two ions aH+ × aCl- (Martz et al., 2010).
Johnson Kenneth S., Plant Joshua N., Maurer Tanya L. (2018). Processing BGC-Argo pH data at the DAC level. Argo data management. https://doi.org/10.13155/57195