A tandem Mg/Ca-clumped isotope approach for palaeotemperature estimation of past climate

用于过去气候古温度估计的串联镁/钙同位素方法

• 批准号: NE/M003752/1
• 负责人: David Hodell
• 金额: $ 39.03万
• 依托单位: University of Cambridge
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2014
• 资助国家: 英国
• 起止时间: 2014 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FM003752%2F1
• 关键词: tandem; Mg; Ca; clumped; isotope

The estimation of the magnitude of global temperature change is central for predicting future climate. However, most numerical climate modeling studies have focused on the instrumental period, which covers only a relatively small amount of time (<100 years). To better understand future climate change and to test the robustness of these models, it is important to reconstruct past temperature changes throughout Earth history. This is not a trivial problem, however, because we must rely on proxies of temperature change that often yield ambiguous results. Over the past decades several proxies of past ocean temperature have been developed including palaeoecological transfer functions, Mg/Ca, and biomarkers (Uk'37, TEX86). Among the newest advances in palaeothermometry is the application of "clumped isotopes" which is based on the abundance of 13C-18O bounds in carbonates. The advantage of this method is that the formation of 13C18O16O2 is temperature dependent but independent of the dissolved inorganic carbon and the d18O of seawater. Therefore, the simultaneous measurement of "clumped isotopes" and traditional oxygen isotopes provides a unique solution to the carbonate palaeotemperature equation by constraining both temperature and d18O of water. The Mg/Ca ratio of foraminiferal calcite has been similarly shown to be temperature dependent. Hence, paired measurements of Mg/Ca and oxygen isotopes from the same foraminiferal specimens permit reconstruction of the oxygen isotopes of the sea water. The main aim of the proposal is to combine Mg/Ca and clumped isotope measurements of the same foraminiferal tests to produce independent estimates of temperature. By combining the Mg/Ca and clumped isotopes palaeotemperature equations, the expected relationship between Mg/Ca and clumped isotopes can be predicted. Adherence to the expected relationship in fossil foraminifera will provide confidence in the palaeotemperature estimates or, if they diverge from the expected relationship, will identify problems with either one or both proxies. Initially, we will test the predicted relationship using modern foraminifera which cover a temperature range from approx. 6 to 28 degree to verify and calibrate the method. Next, we will test the application of the method during the last glacial period using a transect of well-dated sediment cores in the north Atlantic. The magnitude of abrupt climate change events during the last deglacial is still under debate in the scientific community. For example, large discrepancies exist in estimates of tropical cooling inferred from marine (~2-4 degree) and terrestrial (~6-10 degree) archives during these extreme events. This discrepancy may be the result of seasonal bias of the temperature proxies. However, the temperature range is much larger than expected for average seasonal temperature differences in the tropics. This raises the question whether these discrepancies are real or caused by differences in the sensitivity or reliability of specific proxies. With tandem measurements of Mg/Ca and clumped isotopes it will be possible to determine the magnitude of temperature change and estimate its spatial extent during abrupt climate change events of the last glacial. Furthermore, the well-dated cores of the late quaternary provide an ideal test case for our tandem Mg/Ca-clumped isotope palaeothermometer whose successful development and application will permit to investigate many relevant open questions about earth's climate history.

全球温度变化幅度的估计对于预测未来气候是核心。但是，大多数数值气候建模研究都集中在仪器时期，这仅涵盖相对较小的时间（<100年）。为了更好地了解未来的气候变化并测试这些模型的鲁棒性，重要的是重建整个地球历史的过去温度变化。但是，这不是一个微不足道的问题，因为我们必须依靠温度变化的代理，而温度变化通常会产生模棱两可的结果。在过去的几十年中，过去的几个代理已经开发了包括古生态转移功能，mg/ca和生物标志物（UK'37，TEX86）。古热测度法的最新进展之一是应用“集结同位素”，该应用基于碳酸盐中13c-18o的丰度。该方法的优点是形成13C18O16O2取决于温度，但与溶解的无机碳和海水的D18O无关。因此，通过约束水的温度和D18O，同时测量“集结同位素”和传统的氧同位素为碳酸盐古植物方程提供了独特的解决方案。有孔虫方解石的mg/ca比已被类似地证明是温度依赖性的。因此，来自相同有孔虫标本的Mg/Ca和氧同位素的配对测量允许重建海水的氧同位素。该提案的主要目的是结合相同有孔虫测试的Mg/Ca和集成的同位素测量，以产生独立的温度估计值。通过组合Mg/Ca和集成的同位素古植物方程，可以预测Mg/Ca和集成的同位素之间的预期关系。遵守化石有孔虫中预期的关系将对古植物的估计值提供信心，或者，如果它们与预期的关系有所不同，则将确定一个或两个代理的问题。最初，我们将使用现代有孔虫测试预测关系，该关系涵盖了大约的温度范围。 6至28度以验证和校准该方法。接下来，我们将在最后一个冰川期间使用北大西洋良好的沉积物核心的样本测试该方法的应用。在最后一次冰期期间，突然的气候变化事件的幅度仍在科学界争论。例如，在这些极端事件中，从海洋（〜2-4度）和陆地（〜6-10度）档案中推断出的热带冷却中存在巨大差异。这种差异可能是温度代理季节性偏差的结果。但是，对于热带地区的平均季节性温度差异，温度范围比预期的要大得多。这就提出了一个问题，这些差异是由特定代理的敏感性或可靠性差异而引起的还是引起的。通过MG/CA和集成的同位素的串联测量，可以确定温度变化的幅度，并在最后一个冰川的突然气候变化事件中估算其空间范围。此外，晚期晚期良好的核心为我们的串联MG/CA倾斜同位素古热仪提供了理想的测试用例，其成功的开发和应用将允许研究有关地球气候历史的许多相关开放问题。

项目成果

Quantitative estimates of tropical temperature change in lowland Central America during the last 42 ka

• DOI: 10.1016/j.epsl.2016.01.001
• 发表时间: 2016-03
• 期刊: Earth and Planetary Science Letters
• 影响因子: 5.3
• 作者: Anna-Lena Grauel;D. Hodell;S. Bernasconi

Reducing Uncertainties in Carbonate Clumped Isotope Analysis Through Consistent Carbonate-Based Standardization.

• DOI: 10.1029/2017gc007385
• 发表时间: 2018-09
• 期刊: Geochemistry, geophysics, geosystems : G(3)
• 作者: Bernasconi SM;Müller IA;Bergmann KD;Breitenbach SFM;Fernandez A;Hodell DA;Jaggi M;Meckler AN;Millan I;Ziegler M
• 通讯作者: Ziegler M

Coupled Mg/Ca and clumped isotope analyses of foraminifera provide consistent water temperatures

• DOI: 10.1016/j.gca.2018.03.010
• 发表时间: 2018-09-01
• 期刊: GEOCHIMICA ET COSMOCHIMICA ACTA
• 影响因子: 5
• 作者: Breitenbach, Sebastian F. M.;Mleneck-Vautravers, Maryline J.;Hodell, David A.
• 通讯作者: Hodell, David A.

Quantification of paleo-aquifer changes using clumped isotopes in subaqueous carbonate speleothems

• DOI: 10.1016/j.chemgeo.2018.05.046
• 发表时间: 2018-08-20
• 期刊: CHEMICAL GEOLOGY
• 影响因子: 3.9
• 作者: Gazquez, Fernando;Columbu, Andrea;Hodell, David A.
• 通讯作者: Hodell, David A.