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

从有孔虫中的硼同位素比率和浓度重建末次冰期-间冰期过渡期间的海水碳酸盐化学

• 批准号: 316936271
• 负责人: Professor Dr. Jelle Bijma, Ph.D.
• 金额: --
• 依托单位: Alfred-Wegener-Institut (AWI) Helmholtz-Zentrum für Polar- und Meeresforschung
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2016
• 资助国家: 德国
• 起止时间: 2015-12-31 至 2021-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/316936271?language=en
• 关键词: Reconstruction; Seawater; Carbonate; chemistry; during

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.

碳循环扰动（CCP）的症状，无论是自然的还是人类活动引起的全球变暖，海洋酸化（OA）和缺氧。这些结果是一种致命的混合物，因为天然CCP已被确定为地球历史上5次大规模灭绝中至少4次的主要原因（Honisch et al. 2009; Bijma et al. 2013 a）。人类活动释放二氧化碳的速度比过去6500万年，甚至可能是过去3亿年的任何时候都快10倍，使人为碳扰动的管理成为社会的主要挑战之一。为了准确预测人为CCP的后果，首先必须了解地球碳循环的自然汇和源的波动和变化。这需要准确重建海洋碳酸盐化学，因为深海碳储存的变化是解释冰芯记录中观察到的冰期/间冰期大气CO2变化的关键（Köhler等人，2005年; Yu等人，2010年）。在这里，我们建议量化的过程，导致了ca。在冰期/间冰期过渡期大气pCO 2增加100 ppmv。大部分深水都是在南大洋通风的，南大洋的各种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（通过铁施肥和压载），水柱分层的增加减少了从冰川南大洋返回大气的碳泄漏（Keeling和维斯贝克，2001年）。在冰消期，这种深海碳电容器与大气重新连接，并由于不完全的营养利用而导致快速的CO2释气，这是南大洋温暖时期的特征（所谓的高营养低叶绿素（HNLC）区域）。到目前为止，所有这些仍然是假设的，尽管有间接证据支持（Martinez-Boti et al. 2015; Ronge et al. 2015），但没有通过直接重建冰川/间冰期碳酸盐化学演化来证明。我们的建议的总体目标是分析两个独立的碳酸盐化学代用品的底栖和浮游有孔虫测试从沉积物岩心记录最后的G/IG过渡，以量化自然CO2释气，并有助于更好地了解自然碳储存和释放。为了提高重建效果，我们将首次在深海底栖有孔虫上进行原位压力下的d11 B pH和B/Ca碳酸氢根离子校准。我们还将优化方法和分析工具，以实现更小的样本量，从而实现单壳分析。