Ground Truthing the Boron Isotope Paleo-pH Proxy

海洋碳酸盐中的硼同位素可以提供有关过去海洋化学的信息，因为这种同位素在碳酸盐中的含量主要受海洋碳酸盐化学的控制。 然而，迄今为止，尚未对这一替代品进行系统的全球评价。 出于这个原因，来自皇后学院的PI计划通过分析从全球范围内从具有明确水化学性质的地区回收的表层沉积物中获得的浮游和底栖formaminifera来测试硼同位素古pH值代理的实用性。 本研究的结果将提供一个机会来记录响应物种效应、温度和碱性的预测同位素组成的潜在偏差。 此外，PI将进行实验室方解石生长实验，以确定pH值、温度、压力、盐度和生长速率对方解石硼同位素组成的影响。 还将在受控的水组成和温度下进行Orbulina universa和Globigerina bulloides（分别有和没有共生体的物种）的有孔虫培养实验，以评估硼分馏对共生体密度和其他变量的响应。 最后，评价了成岩作用（溶解作用和重结晶作用）对硼同位素组成的影响。 更广泛的影响。 这项研究的结果将确定硼同位素是否可以作为古pH值的替代，以获得古代气候变化的信息，而不是直接的证据。 了解过去地球气候的自然波动对于理解和评估当前全球气候变化的格局和人类活动对全球气候变化的影响至关重要。

ABSTRACTOCE-0326952Boron isotopes in marine carbonates may provide information about past ocean chemistry because the inclusion of this isotope into carbonates is controlled primarily by the carbonate chemistry of the ocean. However, to date no systematic, global evaluations of this proxy have been carried out. For this reason, a PI from Queens College plans to test the utility of the boron isotope paleo-pH proxy by analyzing planktonic and benthic formaminifera obtained from surficial sediments recovered globally from regions with well-defined water chemistries. Results from this study will provide an opportunity to document potential deviations from predicted isotopic compositions in response to species effect, temperature and alkalinity. In addition, the PI will carry out laboratory calcite growth experiments to determine the influence of pH, temperature, pressure, salinity and growth rate on the boron isotope composition of calcite. Foraminifera culture experiments with Orbulina universa and Globigerina bulloides (species with and without symbionts, respectively) also will be done under controlled water composition and temperature to assess boron fractionation in response to symbiont density and other variables. Lastly, the effect of diagenesis (dissolution and recrystallization) on the boron isotope composition will be evaluated. Broader impacts. Results from this study will determine whether boron isotopes can be used as a paleo-pH proxy to obtain information on ancient climate change in lieu of direct evidence. An understanding of past natural fluctuations in the earth's climate is essential to comprehending and evaluating current pattern of, and anthropogenic impacts on, global climate change.