The global oceans serve as the largest sustained natural sink for increasing atmospheric carbon dioxide (CO₂) concentrations. As this CO₂ is absorbed by seawater, it not only reacts causing a reduction in seawater pH (or acidification) but also decreases the carbonate mineral saturation state (Ω), which plays an important role in calcification for many marine organisms. Ocean acidification could affect some of the most fundamental biological and geochemical processes of the sea in coming decades. Observations obtained in situ from Volunteer Observing Ships and multiple geochemical surveys have been extended using satellite remote sensing and modeled environmental parameters to derive estimates of sea-surface alkalinity (A_T) and carbon dioxide partial pressure (pCO_2,sw). Pairing estimates of A_T and pCO_2,sw have permitted characterization of the changes in sea-surface Ω, which have transpired over the past decade throughout the Greater Caribbean Region as a consequence of ocean acidification. The results reveal considerable spatial and temporal variability throughout the region. Despite this variability, we observed a strong secular decrease in aragonite saturation state (Ω_arg) at a rate of approximately −0.012 ± 0.001 Ω_arg yr⁻¹ (r² = 0.97, P < 0.001).