Direct Determination of the pH Distribution in the Glacial Oceans Based on the Boron Isotope Composition of Foraminifera

9402263旨在解释冰芯中记录的大气二氧化碳含量在冰期和间冰期之间存在80ppm差异的Broecker情景可以分为两类，一种涉及海洋的生物泵，另一种涉及海洋的碳酸钙循环。前者受到了最多的关注，但有孔虫的镉浓度和碳同位素测量似乎对他们不利。在某种程度上，后者被立即拒绝，因为深海沉积物的溶解记录似乎与实现观测到的大气二氧化碳变化所需的相当大的CO32含量变化背道而驰。最近，阿彻和迈尔-赖默找到了一种绕过溶解记录限制的方法。它们表明，由于呼吸作用CO2释放到沉积物上部厘米的影响，稳态溶跃层深度可能有较大的变化。这项研究将使用硼同位素方法来确定阿彻和迈尔-赖默方案是否可行。对成对的冰川和全新世有孔虫(包括底栖生物和浮游生物)的初步测量表明，按照阿彻和迈尔-赖默假设的要求，冰川时期海洋的酸碱度高出0.2至0.3个单位。这项研究的主旨是以可达到的最高精度进行更多的此类测量，并探索应用于海洋CaCO3的硼同位素pH法所基于的众多假设的有效性。

9402263 BROECKER Scenarios designed to explain the 80 ppm glacial to interglacial difference in atmospheric CO2 content recorded in ice cores can be placed into tow categories, those involving the ocean's biologic pump and those involving the ocean's CaCO3 cycle. The former group received most attention; but cadmium concentration and carbon isotope measurements on foraminifera appear to rule against them. The latter group have, to some extent, been rejected out of hand because the dissolution record for deep sea sediments appears to dictate against the rather large CO32 content changes required to accomplish the observed atmospheric CO2 change. Recently Archer and Maier-Reimer have found a way around the dissolution record constraint. They show that because of the influence of respiration CO2 released to the upper centimeter of sediment it is possible to have a rather large change in the steady state lysocline depth. This study will employ the boron isotope method to determine whether the Archer and Maier-Reimer scenario is feasible. Preliminary measurements on paired glacial and holocene foraminifera (both benthic and planktonic) suggest that the ocean's pH was, as required by the Archer and Maier-Reimer scenario, 0.2 to 0.3 units higher during glacial time. The thrust of this research is to make more such measurements with the highest attainable accuracy and also to explore the validity of the numerous assumptions on which the boron isotope pH method as applied to marine CaCO3 is based.