Glacial-Interglacial Carbon Reorganization and Carbonate Compensation in the Pacific Ocean

太平洋的冰期-间冰期碳重组和碳酸盐补偿(Pi：T.Maritto)过去海底碳酸钙(CaCO3)溶解和保存的变化为全球碳循环的运作和大气二氧化碳(CO2)水平的控制提供了基本的见解。根据“CaCO3补偿”假说，在最后一次冰川时期，二氧化碳从上层海洋净转移到深海，导致CaCO3在海底溶解，整个海洋的pH升高，从而加剧了冰川大气中的CO2下降。该项目将在赤道太平洋东部深海初步有孔虫痕量金属和贝壳重量工作的基础上，对CaCO3补偿假说的几个方面进行定量测试。该项目将分为四个主要假设的检验：(1)在上一个冰期-间冰期循环中，EEP中的碳酸盐化学与大气中的二氧化碳紧密耦合，在二氧化碳下降期间出现瞬时的碳酸盐离子[CO3]最小值，在二氧化碳上升期间出现[CO3]最大值；(2)终止I和II(去冰期)[CO3]峰值的幅度大致相当于约30微克分子/公斤；(3)冰川终止期间的[CO3]上升与二氧化碳从深海向上层海洋的释放有关，由底栖和浮游有孔虫的碳同位素组成(D13C)记录；和(4)冰川消融后森林的再生产生了终止I和II后的次级[CO3]峰值。这项工作有望极大地有助于理解海洋在大气二氧化碳循环中的作用。如果海洋对人为二氧化碳的封存有任何希望，或者如果未来海洋对二氧化碳吸收的增加影响深海碳酸盐化学，导致对大气二氧化碳的反馈，那么社会最终可能受益于这种知识。该项目将为一名新博士生、一名地质学本科生和一名专业研究助理提供广泛的学习和培训经验。

Glacial-Interglacial Carbon Reorganization and Carbonate Compensation in the Pacific Ocean (PI: T. Marchitto)Past variations in the dissolution and preservation of seafloor calcium carbonate (CaCO3) offer fundamental insights into the workings of the global carbon cycle and the controls on atmospheric carbon dioxide (CO2) levels. According to the 'CaCO3 compensation' hypothesis, there was a net shift of CO2 from the upper ocean into the deep ocean during the last glacial period, resulting in seafloor dissolution of CaCO3 and an increase in whole-ocean pH that compounded the glacial atmospheric CO2 drop. This project will quantitatively test several aspects of the CaCO3 compensation hypothesis, building upon preliminary foraminiferal trace metal and shell weight work in the deep eastern equatorial Pacific (EEP). The project will be divided into the testing of four main hypotheses: (1) carbonate chemistry in the EEP was tightly coupled to atmospheric CO2 over the last glacial-interglacial cycle, with transient carbonate ion [CO3] minima during CO2 drops and [CO3] maxima during CO2 rises; (2) the magnitudes of the Termination I and II (deglacial) [CO3] spikes were roughly equivalent at ~30 umol/kg; (3) [CO3] rises during glacial terminations were associated with the release of CO2 from the deep ocean into the upper ocean, recorded by the carbon isotopic composition (d13C) of benthic and planktonic foraminifera; and (4) regrowth of forests following deglaciation produced secondary [CO3] spikes after Terminations I and II. This work promises to contribute significantly to the understanding of the ocean's role in atmospheric CO2 cycles. Society may ultimately benefit from such knowledge if the oceans hold any hope for sequestration of anthropogenic CO2; or if future increases in CO2 uptake by the oceans impact deep sea carbonate chemistry, resulting in feedbacks on atmospheric CO2. This project will provide extensive learning and training experiences for a new PhD student, a geology undergraduate student, and a professional research assistant.