Testing the amplitude and rapidity of carbonate saturation change and global climate during the high pCO2 Oligocene 'cold house'

测试高 pCO2 渐新世“冷屋”期间碳酸盐饱和度变化和全球气候的幅度和速度

基本信息

批准号：
NE/F003641/1
负责人：
Heiko Pälike
金额：
$ 33.66万
依托单位：
University of Southampton
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2008
资助国家：
英国
起止时间：
2008 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=NE%2FF003641%2F1
关键词：
Testing amplitude rapidity carbonate saturation

项目摘要

The overarching objective of the proposed research is to establish the rapidity and amplitude of variations in ocean acidification during the Oligocene, exploiting the two high-resolution, single site records that have recently been established in the equatorial Pacific by the Ocean Drilling Program, with a view to test recently proposed model hypotheses as to the origin of these fluctuations . Numerous efforts are currently underway to investigate modern changes in atmospheric pCO$_2$, and to decipher their impact on global and local temperature, sea-level, and the hydrological cycle. Yet, pCO$_2$ changes also profoundly affect the Earth System through changes of ocean pH. Indeed, the impacts of ocean acidification are additional to, and may exacerbate, the effects of climate change, as recently established by a working group of the Royal Society (2005). Geological records provide the means to answer some of the key questions that relate to the quantification of the acidification process, and what measures of mitigation might be necessary, in particular: How fast is fossil fuel (or added carbonic acid) neutralised? What is the effect of CaCO$_3$ buffering on oceanic carbonate ion saturation (and in turn atmospheric pCO$_2$)? The large number of feedback components that connect the global carbon cycle, atmospheric pCO$_2$, temperature, dissolved oceanic [CO$_3^{2-}$] and pH need to be constrained by present-day measurements as well as data from the geological archive in order to advance the prediction of timing and amplitude of future changes. Previous reconstructions of CCD and lysocline variations have principally been following two angles of attack: a geochemical approach using boron isotopes and their sensitivity with respect to ocean water pH, or a sedimentological proxy approach, mapping the occurrence and absence of calcium carbonate in sediments. The latter approach generally provides a low-resolution but large regional perspective. Indeed, recent research by the PIs has resulted in the first constraints on a coupling between the lysocline and the onset of the Oligocene ``cold-house'' during a rapid and extensive simultaneous deepening of the CCD of $>$1 km, and a shift in benthic oxygen isotope values towards greater values by more than 1 permille. Here we propose to exploit, in a novel way, an ideal ``natural laboratory'' setting to reconstruct variations in the oceanic lysocline and the effect of these variations on a palaeoclimate proxy (oxygen isotopes) during the Oligocene, as provided by drill sites 1218 and 1219 in the Equatorial Pacific. Both sites record high-resolution climate proxy records for the Oligocene, but with a vertical offset in palaeodepth of about 300 to 500 metres. Current hypotheses predict that this vertical offset should result in a difference in carbonate dissolution affecting both CaCO$_3$ flux, and stable isotope measurements of d13C and d18O in bulk and benthic foraminiferal calcite. Data from these sites will provide the first opportunity to test recently modeled short-term oceanic [CO$_3^{2-}$] (and thus lysocline) variations on glacial-interglacial (kyr) time scales \citep{Palike2006}, within a setting of higher pCO$_2$ ``cold-house'' conditions, and thus provide a more realistic approach as to what future changes in ocean acidification state might entail, and on what time scales natural variability occurs despite the buffering effect of carbonate dissolution at the sea-floor.

拟议研究的总体目标是建立渐新世期间海洋酸化变化的迅速性和幅度，利用了海洋钻探计划在赤道太平洋地区最近在赤道太平洋地区建立的两个高分辨率的单个现场记录，以期测试最近提出的这些波动的模型，以实现这些波动的来源。目前正在努力研究大气PCO $ _2 $的现代变化，并破译其对全球和局部温度，海平面和水文周期的影响。然而，PCO $ _2 $变化也通过更改海洋pH来深刻影响地球系统。确实，海洋酸化的影响是皇家学会（2005）最近确立的，并且可能加剧气候变化的影响。地质记录提供了回答与酸化过程量化有关的一些关键问题的方法，以及可能需要采取哪些缓解措施，特别是：化石燃料（或添加的碳酸）中和？ CACO $ _3 $缓冲对海洋碳酸盐离子饱和的影响是什么？连接全球碳循环，大气PCO $ _2 $，温度，溶解的海洋[CO $ _3^{2 - } $]的大量反馈组件，以及pH值需要受到当今测量值以及地质档案的数据来限制，以促进未来变化的预测和幅度。以前的CCD和裂解素变化的重建主要是遵循两个攻击角度：一种使用硼同位素的地球化学方法及其对海洋水pH的敏感性，或者是沉积学代理方法，映射了沉积物中碳酸盐的出现和缺失。后一种方法通常提供了低分辨率但很大的区域视角。确实，PIS的最新研究导致对lysocline和渐新世发作之间的耦合的第一构成，在快速，广泛的同时加深了CCD $> $ 1 km的同时加深$ 1 km，而甲属氧气值的变化更大，而甲属氧气值则更大。在这里，我们建议以一种新颖的方式利用理想的“天然实验室”设置，以重建海洋lysocline的变化，以及这些变化对在赤道1218和1219在赤道PACICIC提供的渐新世期间渐新世期间渐新世期间古气候代理（氧同位素）的影响。这两个地点都记录了渐新世的高分辨率气候代理记录，但在大约300至500米的古redeodepth中垂直偏移。当前的假设预测，这种垂直偏移应导致碳酸盐溶解差异，影响可可$ _3 $通量，以及在散装和底栖有孔虫方解石中D13C和D18O的稳定同位素测量。来自这些站点的数据将为最近的测试最近建模的短期海洋[CO $ _3^{2 - } $]（以及因此在冰川 - 裂纹（KYR）时间缩放\ citep {palike2006}的情况下，在较高的pco $ _2 $ _2 $ _2 $ _ 2 $``````2 $'）'）''的环境中的变化了，从而提供了一个较高的pco $ _2 $ _ 2 $````''2 $ _2 $''''''''''''''''''状态可能需要，尽管在海底碳酸盐溶解的缓冲作用，但在什么时间范围内发生自然变异性。