BUSCADOR RECOLECTA

Digital.CSIC. Repositorio Institucional del CSIC

oai:digital.csic.es:10261/274757

15 pages, 5 figures, 1 table.-- This publication is licensed under CC-BY 4.0, The spectrophotometric methodology for carbonate ion determination in seawater was first published in 2008 and has been continuously evolving in terms of reagents and formulations. Although being fast, relatively simple, affordable, and potentially easy to implement in different platforms and facilities for discrete and autonomous observations, its use is not widespread in the ocean acidification community. This study uses a merged overdetermined CO2 system data set (carbonate ion, pH, and alkalinity) obtained from 2009 to 2020 to assess the differences among the five current approaches of the methodology through an internal consistency analysis and discussing the sources of uncertainty. Overall, the results show that none of the approaches meet the climate goal (± 1 % standard uncertainty) for ocean acidification studies for the whole carbonate ion content range in this study but usually fulfill the weather goal (± 10 % standard uncertainty). The inconsistencies observed among approaches compromise the consistency of data sets among regions and through time, highlighting the need for a validated standard operating procedure for spectrophotometric carbonate ion measurements as already available for the other measurable CO2 variables., E.F.G. was supported by a Personal Técnico de Apoyo contract (PTA2016-12441-I) and N.M.F. was supported by a Juan de la Cierva postdoctoral contract (FJCI2015-24394), both from the Spanish Ministry of Science, Innovation and Universities and GAIN Grupo de Referencia Competitiva IN607A 2018/2 from Xunta de Galicia. M.I.G.-I. was supported by NOAA’s Ocean Acidification Program (OAP) via Award No. NA17OAR0170332, and by NERC’s CUSTARD (Carbon Uptake and Seasonal Traits of Antarctic Remineralisation Depths) project NE/P021263/1. A.E.R.H. was supported via the 2018 NF-POGO Shipboard Fellowship. F.F.P. was supported by the BOCATS2 (PID2019-104279GB-C21/AEI/10.13039/501100011033) project funded by MCIN/AEI/10.13039/501100011033 and contributing to WATER:iOS CSIC PTI. M.A. was supported by IEO RADIALES, RADPROF, and MEDSHIP18 programs. The MEDWAVES cruise was funded under the ATLAS project (Grant Agreement No. 678760). The RADPROF (2020) cruise was funded under the INTERREG Atlantic Area iFADO project., With the institutional support of the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S), Peer reviewed