evidence: The uptake of carbon by the oceans affects marine chemistry via ocean acidification (Gattuso and Buddemeier, 2000; Orr et al., 2005; Doney et al., 2009), a process that increases seawater concentrations of CO2, H+, and and reduces pH and ion concentrations. The oceans have absorbed approximately 30 % of anthropogenic carbon emissions since the pre-industrial era (Sabine et al., 2004; Khatiwala et al., 2009, 2013; Gruber et al., 2019), resulting in global surface pH declines of approximately 0.1 units (Bindoff et al., 2007). Declines in global open ocean surface pH are 0.018 units per decade over 1991–2011 (Lauvset et al. 2015), with individual time series stations exhibiting declines of 0.017 to 0.027 units per decade (Bindoff, et al., in press). Earth system models have projected twenty-first century global surface ocean pH declines of up to 0.33 units under previous high-emissions scenarios (Bopp et al., 2013), with associated changes in the seasonal cycles of seawater carbonate chemistry (McNeil and Sasse, 2016; Kwiatkowski and Orr, 2018; Landschützer et al., 2018).