Seawater carbonate system considerations for ocean alkalinity enhancement research

Abstract. Ocean alkalinity enhancement (OAE) is a proposed marine carbon dioxide removal (mCDR) approach that has the potential for large-scale uptake of significant amounts of atmospheric carbon dioxide (CO2). Removing anthropogenic legacy CO2 will be required to stabalise global surface temperatures below the 1.5–2 °C Paris Agreement target of 2015. In this chapter we describe the impacts of various OAE feedstocks on seawater carbonate chemistry, as well as pitfalls that need to be avoided during sampling, storage and measurement of the four main carbonate chemistry parameters, i.e. dissolved inorganic carbon (DIC), total alkalinity (TA), pH and CO2 fugacity (fCO2). Finally, we also discuss considerations in regard to calculating carbonate chemistry speciation from two measured parameters.