Current CaCO3 dissolution at the seafloor caused by anthropogenic CO2
Current CaCO3 dissolution at the seafloor caused by anthropogenic CO2
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DOI：
10.1073/pnas.1804250115
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发表时间：
2018-10
期刊：
影响因子：
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通讯作者：
O. Sulpis;B. Boudreau;A. Mucci;Chris Jenkins;D. Trossman;B. Arbic;R. Key
中科院分区：
文献类型：
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作者：
O. Sulpis;B. Boudreau;A. Mucci;Chris Jenkins;D. Trossman;B. Arbic;R. Key
地质记录中有许多“温室期”和海洋酸化事件的例子，腐蚀性（富含二氧化碳）的海底沃茨的扩散促进了输送到海底或深海沉积物中的碳酸钙矿物的溶解。沉积CaCO 3的溶解中和了过量的CO2，从而防止了失控的酸化，并在数百年至数千年的时间尺度内作为负反馈机制调节大气CO2水平。我们报告了一个基于观测的指示和量化的显着CaCO 3溶解在海底所造成的人为CO2。这种溶解已经发生在深海的各个地方，特别是在北方大西洋和南大洋附近，那里的底层沃茨很年轻，富含人为二氧化碳。海洋对人为CO2的吸收导致CaCO 3矿物的pH值、碳酸盐离子浓度和饱和状态降低，从而导致这些矿物在深海底的溶解增加。这种额外的溶解将在人造CO2的中和中起重要作用。然而，目前尚无对深海海底人为CaCO 3溶解程度的一致评估。在这里，最近的数据库的底层水化学，底栖电流，和CaCO 3含量的深海沉积物相结合的速率模型，以获得全球分布的底栖方解石溶解速率，并获得初步确认的人为成分。通过比较工业化前与当今的速率，我们确定，显着的人为溶解现在发生在北大西洋西部，在其最激烈的位置，总海底溶解量的40-100%。在这些位置，方解石补偿深度上升了1300米。在大西洋、印度洋和太平洋南部的各个热点也发现海底溶解增加。我们的研究结果限制了未来对海洋酸化的预测，对底栖钙化物的命运产生了影响，并表明人类活动的副产品目前正在改变深海的地质记录。
Significance The geological record contains numerous examples of “greenhouse periods” and ocean acidification episodes, where the spreading of corrosive (CO2-enriched) bottom waters enhances the dissolution of CaCO3 minerals delivered to the seafloor or contained within deep-sea sediments. The dissolution of sedimentary CaCO3 neutralizes excess CO2, thus preventing runaway acidification, and acts as a negative-feedback mechanism in regulating atmospheric CO2 levels over timescales of centuries to millennia. We report an observation-based indication and quantification of significant CaCO3 dissolution at the seafloor caused by man-made CO2. This dissolution is already occurring at various locations in the deep ocean, particularly in the northern Atlantic and near the Southern Ocean, where the bottom waters are young and rich in anthropogenic CO2. Oceanic uptake of anthropogenic CO2 leads to decreased pH, carbonate ion concentration, and saturation state with respect to CaCO3 minerals, causing increased dissolution of these minerals at the deep seafloor. This additional dissolution will figure prominently in the neutralization of man-made CO2. However, there has been no concerted assessment of the current extent of anthropogenic CaCO3 dissolution at the deep seafloor. Here, recent databases of bottom-water chemistry, benthic currents, and CaCO3 content of deep-sea sediments are combined with a rate model to derive the global distribution of benthic calcite dissolution rates and obtain primary confirmation of an anthropogenic component. By comparing preindustrial with present-day rates, we determine that significant anthropogenic dissolution now occurs in the western North Atlantic, amounting to 40–100% of the total seafloor dissolution at its most intense locations. At these locations, the calcite compensation depth has risen ∼300 m. Increased benthic dissolution was also revealed at various hot spots in the southern extent of the Atlantic, Indian, and Pacific Oceans. Our findings place constraints on future predictions of ocean acidification, are consequential to the fate of benthic calcifiers, and indicate that a by-product of human activities is currently altering the geological record of the deep sea.