The net uptake of carbon dioxide (CO₂) from the atmosphere is changing the ocean's chemical state. Such changes, commonly known as ocean acidification, include a reduction in pH and the carbonate ion concentration ([CO₃²⁻]), which in turn lowers oceanic saturation states (Ω) for calcium carbonate (CaCO₃) minerals. The Ω values for aragonite (Ω_aragonite; one of the main CaCO₃ minerals formed by marine calcifying organisms) influence the calcification rate and geographic distribution of cold-water corals (CWCs), important for biodiversity. Here, high-quality measurements, collected on thirteen cruises along the same track during 1991–2018, are used to determine the long-term changes in Ω_aragonite in the Irminger and Iceland Basins of the North Atlantic Ocean, providing the first trends of Ω_aragonite in the deep waters of these basins. The entire water column of both basins showed significant negative Ω_aragonite trends between −0.0014 ± 0.0002 and −0.0052 ± 0.0007 per year. The decrease in Ω_aragonite in the intermediate waters, where nearly half of the CWC reefs of the study region are located, caused the Ω_aragonite isolines to rapidly migrate upwards at a rate between 6 and 34 m per year. The main driver of the decline in Ω_aragonite in the Irminger and Iceland Basins was the increase in anthropogenic CO₂. But this was partially offset by increases in salinity (in Subpolar Mode Water), enhanced ventilation (in upper Labrador Sea Water), and increases in alkalinity (in classical Labrador Sea Water, cLSW; and overflow waters). We also found that water mass aging reinforced the Ω_aragonite decrease in cLSW. Based on these Ω_aragonite trends over the last three decades, we project that the entire water column of the Irminger and Iceland Basins will likely be undersaturated for aragonite when in equilibrium with an atmospheric mole fraction of CO₂ (xCO₂) of ~880 ppmv, corresponding to climate model projections for the end of the century based on the highest CO₂ emission scenarios. However, intermediate waters will likely be aragonite undersaturated when in equilibrium with an atmospheric xCO₂ exceeding ~630 ppmv, an xCO₂ level slightly above that corresponding to 2 °C global warming, thus exposing CWCs inhabiting the intermediate waters to undersaturation for aragonite.

大气中二氧化碳（CO ₂）的净吸收正在改变海洋的化学状态。此类变化通常称为海洋酸化，包括pH值降低和碳酸盐离子浓度（[CO ₃ ^2- ]），进而降低碳酸钙（CaCO ₃）矿物的海洋饱和态（Ω）。对于文石Ω值（Ω_文石;主要的CaCO之一₃由海洋钙化生物形成矿物质）影响钙化率和冷水珊瑚（CWCs），生物多样性重要的地理分布。在这里，使用高质量的测量值（在1991-2018年期间沿着同一航迹的13条航道上收集）来确定Ω的长期变化。_文石在北大西洋的Irminger和冰岛盆地，提供Ω的第一个趋势_文石这些盆地的深水区。两个盆地的整个水柱每年在-0.0014±0.0002和-0.0052±0.0007之间显示出显着的负Ω_文石趋势。研究区域中近一半的CWC礁所在的中间水域中的Ω_文石的减少导致Ω_文石等值线以每年6到34 m的速度迅速向上迁移。埃尔明格和冰岛盆地Ω_文石下降的主要原因是人为CO ₂的增加。但这被盐分的增加（在亚极性模式下的水），通风增强（在上拉布拉多的海水中）和碱度的增加（在经典的拉布拉多海水，cLSW和溢流水中）所部分抵消。我们还发现水质老化增强了cLSW中Ω_文石的减少。根据过去三十年来的这些Ω_文石趋势，我们预测，当大气中的CO ₂（xCO ₂）摩尔分数约为880 ppmv时，文石和冰岛盆地的整个水柱中文石的饱和度可能都不足。，对应于本世纪末基于最高CO _2的气候模型预测排放情景。但是，当与大气中的xCO ₂超过约630 ppmv平衡时，中间水很可能是文石欠饱和的，xCO _2的水平略高于对应于2°C全球变暖的水平，因此使居住在中间水的CWC暴露于文石的欠饱和状态。