Evidence for a higher pH in the glacial ocean from boron isotopes in foraminifera
Evidence for a higher pH in the glacial ocean from boron isotopes in foraminifera
复制标题
DOI：
10.1038/373234a0
复制
发表时间：
1995-01
期刊：
影响因子：
64.8
通讯作者：
A. Sanyal;N. Hemming;G. Hanson;W. Broecker
中科院分区：
文献类型：
--
作者：
A. Sanyal;N. Hemming;G. Hanson;W. Broecker
过去海洋pH值变化的记录应该可以让我们深入了解海洋碳酸盐化学是如何随着时间的推移而变化的。后者与大气CO2含量的变化有关，例如在末次冰期-间冰期过渡期间发生的变化1。先前的研究2，3表明，海水和沉淀碳酸盐矿物之间的硼同位素分馏是pH值依赖性的。这一发现已被用于重建在过去的2000万年的海洋pH值的演变，通过分析有孔虫4碳酸盐外壳中的硼同位素。在这里，我们使用相同的方法来估计末次冰期和全新世之间海洋pH值的变化。我们估计，在末次冰期，大西洋和太平洋的pH值高出0.3±0.1个单位。伴随的碳酸根离子浓度的变化足以解释冰期1期间大气pco 2的减少。这些结果是一致的假设5，即低CO2含量的冰川大气是由有机碳碳酸盐的比例增加的“雨”到海底，这导致了碳酸盐离子浓度的增加（从而在pH值）的深水没有相应的增加溶跃层深度。
RECORDS of past changes in the pH of the oceans should provide insights into how the carbonate chemistry of the oceans has changed over time. The latter is related to changes in the atmospheric CO2content, such as that which occurred during the last glacial-interglacial transition1. Previous studies2,3have shown that the fractionation of boron isotopes between sea water and precipitated carbonate minerals is pH-dependent. This finding has been used to reconstruct the evolution of ocean pH over the past 20 million years by analyses of boron isotopes in the carbonate shells of foraminifera4. Here we use the same approach to estimate changes in ocean pH between the last glacial and the Holocene period. We estimate that the deep Atlantic and Pacific oceans had a pH 0.3±0.1 units higher during the last glaciation. The accompanying change in carbonate ion concentration is sufficient to account for the decrease in atmosphericpco2during the glacial period1. These results are consistent with the hypothesis5that the low CO2content of the glacial atmosphere was caused by an increased ratio of organic carbon to carbonate in the 'rain' to the sea floor, which led to an increase in carbonate ion concentration (and thus in pH) of deep water without a corresponding increase in the lysocline depth.