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

可以说，更好地了解地球过去的自然波动？S气候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，从而提高与人为增加二氧化碳相关的全球气候变化的能力。特别令人关切的是，海洋酸化对珊瑚、翼足类、有孔虫和钙藻等海洋钙化物的潜在影响。工业革命以来海洋酸化的实际程度仍然没有得到很好的量化。在这个项目中，哥伦比亚大学拉蒙特·多尔蒂地球天文台的研究人员将通过实验室实验培养和来自墨西哥湾的高分辨率沉积物岩心相结合，研究拟议中的B/Ca古代用品的稳健性。一项初步研究表明，这一指标有可能反映表层海水pH值和大气二氧化碳浓度的冰期/间冰期变化。然而，浮游有孔虫贝壳中的硼似乎也受到温度的影响，盐度的变化改变了海水中的硼浓度。由于海洋中pH、温度和盐度的变化是一致的，因此只能在实验室中量化各自对B/Ca的影响，因为可以单独选择参数。因此，拟议研究的第一步是在实验室受控条件下的代理验证。如果B/Ca代用品的质量在实验室培养中得到确认，并且效果可以量化，则B/Ca代用品可能比B同位素/古pH代用品有几个优势：B/Ca分析速度快得多，需要更少的样品材料，而且代用品可能不受沉积物中溶解的影响。就更广泛的影响而言，显然，海水的酸碱状态对海洋学的所有分支学科和各种全球环境研究学科都具有根本重要性。该项目将以多个机构间合作为特色，并将提供一名研究生的培训和支助。

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.