Ocean Acidification- Category 1: Real time assessment of ocean acidification proxies and their incorporation in the marine sediment record

在过去的两个世纪里，二氧化碳大量而迅速地释放到大气中，并因此被海洋吸收了其中很大一部分，这导致了海洋化学的可测量变化，最明显的是pH值和碳酸盐离子浓度的下降。在过去200年中，大气中二氧化碳的这种变化及其对海水化学的伴随影响并不是唯一的，而是在整个地质历史中经常发生的。量化海洋对这种自然发生的大气二氧化碳变化的反应，为模拟和预测与人为二氧化碳增加有关的海洋化学的未来变化提供了有价值的见解。本研究利用15年时间序列的沉积物捕集器样本和作为Cariaco盆地海洋时间序列一部分的每两周收集的水柱化学测量数据，研究了三种碳酸盐离子和pH指标（浮游有孔虫壳的重量、B/Ca和硼同位素组成）。这些结果将与每月在时间序列站点进行的上层水柱碳酸盐离子和pH值测量进行比较。在Cariaco盆地中积累的高沉积速率层状沉积物将用于直接比较这三种有孔虫pH指标的变化与过去两个世纪的大气CO2记录之间的变化，在此期间CO2增加了~100 ppmv。研究的最终结果将是对这些广泛使用的pH代理进行深入的现场校准。资金支持研究生，并为本科生参与研究提供机会。

The large and rapid release of CO2 into the atmosphere over the past two centuries and resultant uptake of a significant fraction of this by the oceans have resulted in measurable changes in ocean chemistry, most notably decreases in both pH and carbonate ion concentration. This change in atmospheric CO2 during the last 200 years and its concomitant effect on seawater chemistry are not unique but rather have occurred frequently throughout geologic history. Quantifying the response of the oceans to such naturally occurring changes in atmospheric CO2 provides valuable insights for modeling and predicting future changes in ocean chemistry associated with anthropogenic increases in CO2. This work examines three carbonate ion and pH proxies (weight, B/Ca and boron isotope composition of planktonic foraminiferal shells) using the 15-year time series of sediment trap samples and water column chemistry measurements collected biweekly as part of the Cariaco Basin ocean time series. These results will be compared to monthly measurements of upper water column carbonate ion and pH made at the time series site. High deposition rate, laminated sediments accumulating in the Cariaco Basin will be used to make a direct comparison between changes in these three foraminiferal pH proxies and the atmospheric CO2 record for the last two centuries, a period during which CO2 has increased by ~100 ppmv. The end product of the research will be an in-depth field-calibration of these widely used pH proxies. Funding supports a graduate student, and provides opportunities for undergraduate involvement in research.