Reconstruction of Seawater Carbonate chemistry during the last Glacial-Interglacial transition from Boron isotopic ratios and concentrations in foraminifera

碳循环扰动（CCP）的症状是全球变暖、海洋酸化（OA）和缺氧，无论是自然的还是由人类活动引起的。事实证明，这是一种致命的混合，因为天然CCP已被确定为地球历史上5次大灭绝中至少4次的主要原因（Honisch et al. 2009; Bijma et al. 2013）。人类活动释放二氧化碳的速度比过去6500万年的任何时候都要快10倍，可能比过去300迈里的任何时候都快，这使得管理人为碳扰动成为社会的主要挑战之一。为了准确预测人为碳循环的后果，首先了解地球碳循环的自然汇和源的波动和变率至关重要。这需要精确重建海洋碳酸盐化学，因为深海碳储量的变化是解释冰芯记录中观测到的冰期/间冰期大气CO2变化的关键（Köhler et al. 2005; Yu et al. 2010）。在此，我们建议量化导致冰期/间冰期过渡期间大气二氧化碳分压增加约100ppmv的过程。大部分深水处于通风状态的南大洋的过程被怀疑在这方面发挥了核心作用。人们认为，缓慢的冰川海洋可以储存更多的碳，生物泵更有效（通过铁施肥和压舱），水柱分层的增加减少了从冰川南大洋泄漏回大气的碳（Keeling和Visbeck 2001）。在冰川消融期间，这个深海碳电容器与大气重新连接，由于养分利用不完全，导致CO2快速释放，这是南大洋在温暖时期（所谓的高营养低叶绿素（HNLC）区域）的特征。迄今为止，尽管有间接证据支持（Martinez-Boti et al. 2015; Ronge et al. 2015），但所有这些都只是假设，而不是通过直接重建冰期/间冰期碳酸盐化学演化来证明。我们提案的总体目标是分析两个独立的碳酸盐化学指标，这些指标来自记录最后G/IG转变的沉积物岩心的底栖生物和浮游有孔虫测试，以量化自然二氧化碳排放，并有助于更好地了解自然碳储存和释放。为了改进重建，我们将在原位压力下对深海底栖有孔虫进行第一次d11B pH和B/Ca碳酸氢盐离子校准。我们还将优化方法和分析工具，以实现更小的样本量，允许单壳分析。

The symptoms of carbon cycle perturbations (CCP), either natural or induced by human activities are global warming, ocean acidification (OA) and dysoxia. These turn out to be a deadly mix as natural CCP have been identified as the main cause of at least 4 of the 5 mass extinctions in Earth history (Honisch et al. 2009; Bijma et al. 2013a). Anthropogenic activities are releasing CO2 ten times faster than at any time in the last 65 million years, and possibly the last 300 Myr, making the management of the anthropogenic carbon perturbation one of societies major challenges. To accurately project the consequences of anthropogenic CCP, it is vital to first understand the fluctuations and variability of the natural sinks and sources of the Earths carbon cycle. This requires accurate reconstruction of the oceanic carbonate chemistry because changes in the carbon storage in the deep ocean are the key to explain the glacial/interglacial atmospheric CO2 variations observed in ice core records (Köhler et al. 2005; Yu et al. 2010). Herein, we propose to quantify the processes that led to the ca. 100ppmv increase in atmospheric pCO2 over the glacial/interglacial transition. Processes in the Southern Ocean, where most of the deep water is ventilated, are suspected to play a central role in this regard. It is believed that the sluggish glacial ocean could store more carbon, that the biological pump was more efficient (through iron fertilization and ballasting) and that increased stratification of the water column reduced carbon leakage from the glacial Southern Ocean back to the atmosphere (Keeling and Visbeck 2001). During the deglaciation, this deep ocean carbon capacitor becomes reconnected with the atmosphere and leads to rapid CO2 outgassing because of incomplete nutrient utilization, which is characteristic for the Southern Ocean during warm periods (so called High Nutrient Low Chlorophyll (HNLC) region). To date, all of this remains hypothetical, albeit supported by circumstantial evidence (Martinez-Boti et al. 2015; Ronge et al. 2015), but not proven by direct reconstructions of the glacial/interglacial carbonate chemistry evolution. The overarching goal of our proposal is to analyse two independent carbonate chemistry proxies on benthic and planktonic foraminiferal tests from sediment cores recording the last G/IG transition in order to quantify natural CO2 outgassing and contribute to a better understanding of natural carbon storage and release. In order to improve the reconstructions, we will produce the first d11B pH and B/Ca bicarbonate ion calibration on deep sea benthic foraminifera under in situ pressure. We will also optimize the methods and the analytical tools towards smaller sample size, allowing for single shell analysis.