Technical note: Assessment of float pH data quality control methods – a case study in the subpolar northwest Atlantic Ocean
Since a pH sensor has become available that is principally suitable for use on demanding autonomous measurement platforms, the marine CO 2 system can be observed independently and continuously by Biogeochemical Argo floats. This opens the potential to detect variability and long-term changes in inte...
| Published in: | Biogeosciences |
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| Main Authors: | , , , , |
| Format: | Article in Journal/Newspaper |
| Language: | English |
| Published: |
Copernicus Publications
2024
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| Subjects: | |
| Online Access: | https://doi.org/10.5194/bg-21-1191-2024 https://doaj.org/article/53eb6cba29d14aa393455dec7d30fdd6 |
| Summary: | Since a pH sensor has become available that is principally suitable for use on demanding autonomous measurement platforms, the marine CO 2 system can be observed independently and continuously by Biogeochemical Argo floats. This opens the potential to detect variability and long-term changes in interior ocean inorganic carbon storage and quantify the ocean sink for atmospheric CO 2 . In combination with a second parameter of the marine CO 2 system, pH can be a useful tool to derive the surface ocean CO 2 partial pressure ( p CO 2 ). The large spatiotemporal variability in the marine CO 2 system requires sustained observations to decipher trends and study the impacts of short-term events (e.g., eddies, storms, phytoplankton blooms) but also puts a high emphasis on the quality control of float-based pH measurements. In consequence, a consistent and rigorous quality control procedure is being established to correct sensor offsets or drifts as the interpretation of changes depends on accurate data. By applying current standardized routines of the Argo data management to pH measurements from a pH / <svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="8pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="fb147fccdcf98a9911cf3d26a8f6dc33"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="bg-21-1191-2024-ie00001.svg" width="8pt" height="14pt" src="bg-21-1191-2024-ie00001.png"/></svg:svg> O 2 float pilot array in the subpolar North Atlantic Ocean, we assess the uncertainties and lack of objective criteria associated with the standardized routines, notably the choice of the reference method for the pH correction (CANYON-B, LIR-pH, ESPER-NN, and ESPER-LIR) and the reference depth for this adjustment. For the studied float array, significant differences ranging between ca. 0.003 pH units and ca. 0.04 pH units are observed between the four reference methods which have been proposed to correct float pH data. Through comparison against discrete and underway pH data from other ... |
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