Ocean acidification is described as “the other CO₂ problem”, with impacts on a diverse array of marine life and the ecosystems and communities they support. However, instrumental records of ocean pH change are relatively limited, spanning only a few decades and regions, and challenging our ability to distinguish the degree of anthropogenic acidification from natural variability. As one of the primary paleoclimate archives, the calcium carbonate shells and skeletons of marine calcifying organisms (e.g. foraminifera, corals, etc.) can record multiple facets of the climate system with their isotopic and elemental compositions. In particular, the boron isotopic composition (δ¹¹B) and concentration (B/Ca) of marine carbonates have become widely used in recent years as proxies for seawater pH and carbonate chemistry in paleoenvironmental reconstructions. The carbon isotopic composition (δ¹³C) of marine calcifiers can also be used as an indicator of oceanic uptake of anthropogenic CO₂ (the Suess effect), while the size normalised weight (SNW) of foraminifera is used to evaluate the impact of ocean acidification on their calcification. In this study, we present detailed reconstructions of ocean pH and carbonate chemistry with decadal to sub-decadal resolution spanning multiple centuries from the North Atlantic (Gulf Stream & Labrador Current regions). These reconstructions are based on high precision measurements on small foraminifera samples from high-resolution sediment cores. By combining these datasets, we document natural variability in ocean pH, identify the timing of abrupt shifts, and evaluate biological responses. Our results provide a detailed record of ocean pH variations in the open ocean settings, tracking atmospheric CO₂ rise, and offer new insights into the recent history and potential future of the ocean carbon sink.