Validation of the B/Ca proxy for surface seawater pH and application to measure anthropogenic ocean acidification

可以说，更好地了解过去地球气候的自然波动及其与温室气体的关系将增强限制未来对海洋和大气化学的影响的能力，从而增强限制与人为添加二氧化碳有关的全球气候变化的能力。人们特别关注海洋酸化对珊瑚、翼足类、有孔虫和钙质藻类等海洋钙化物的潜在影响。自工业革命以来海洋酸化的实际程度仍然很难量化。在这个项目中，哥伦比亚大学拉蒙特·多尔蒂地球观测站的研究人员将通过实验实验室培养物和来自墨西哥湾的高分辨率沉积物岩心的结合，研究拟议的 B/Ca 古代理的稳健性。 一项试点研究表明，该指标有可能反映冰川/间冰期地表海水 pH 值和大气 pCO2 的变化。然而，浮游有孔虫壳中硼的结合似乎也受到温度的影响，盐度的变化会改变海水硼的浓度。由于海洋中的 pH、温度和盐度会同时变化，因此只能在实验室中量化各自对 B/Ca 的影响，才能单独选出参数。因此，拟议研究的第一步是在实验室受控条件下进行替代验证。如果 B/Ca 替代物的质量在实验室培养中得到确认，并且可以量化其效果，则 B/Ca 比硼同位素/古 pH 替代物具有多个优势：B/Ca 分析速度更快，需要更少的样品材料，并且替代物可能不会受到沉积物中溶解的影响。就更广泛的影响而言，很明显，海水的酸碱状态对于海洋学的所有分支学科以及各种全球环境研究学科都至关重要。 该项目将以多个机构间合作为特色，并将为研究生提供培训和支持。

Arguably, a better knowledge of past natural fluctuations in the earth?s climate and its relation to greenhouse gases will enhance the ability to constrain future impacts on ocean and atmospheric chemistry, and thus global climate change related to anthropogenic additions of CO2. Particular concern exists regarding the potential impact of ocean acidification on marine calcifiers such as corals, pteropods, foraminifers and calcareous algae. The actual extent of ocean acidification since the industrial revolution is still poorly quantified. In this project, researchers at the Lamont Doherty Earth Observatory of Columbia University will study the robustness of a proposed B/Ca paleoproxy through a combination of experimental laboratory cultures and a high-resolution sediment core from the Gulf of Mexico. A pilot study has shown that this proxy has the potential to reflect glacial/interglacial changes of surface seawater pH and atmospheric pCO2. However, the incorporation of boron into planktonic foraminifer shells also seems to be affected by temperature, and salinity variations change the seawater boron concentration. Because pH, temperature and salinity change in unison in the ocean, quantification of the respective effects on B/Ca can only be quantified in the laboratory, were parameters can be singled out. The first step of the proposed research is therefore the proxy validation under controlled conditions in the laboratory. If the quality of the B/Ca proxy is confirmed in laboratory culture and effects can be quantified, B/Ca could have several advantages over the boron isotope/paleo-pH proxy: B/Ca analyses are much faster, require less sample material, and the proxy may not be affected by dissolution in the sediment. In terms of broader impacts, it is clear that the acid-base state of seawater is of fundamental importance to all subdisciplines of oceanography and to a wide variety of global environmental research disciplines. The project will feature multiple inter-institutional collaborations and will provide for the training and support of a graduate student.