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至关重要。然而，大多数数值气候模拟研究都集中在仪器周期上，该周期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稳健性，重建整个地球历史上过去的温度变化非常重要。然而，这不是一个小问题，因为我们必须依赖温度变化的代理，而这通常会产生不明确的结果。在过去的几十年中，已经开发了一些过去海洋温度的替代指标，包括古生态传递函数、Mg/Ca 和生物标记（Uk'37、TEX86）。古测温学的最新进展之一是基于碳酸盐中 13C-18O 结合丰度的“簇同位素”的应用。该方法的优点是 13C18O16O2 的形成与温度有关，但与溶解的无机碳和海水的 d18O 无关。因此，“簇同位素”和传统氧同位素的同时测量通过限制水的温度和d18O为碳酸盐古温度方程提供了独特的解决方案。有孔虫方解石的 Mg/Ca 比率已类似地显示为温度依赖性。因此，对同一有孔虫标本的 Mg/Ca 和氧同位素进行配对测量可以重建海水的氧同位素。该提案的主要目的是将相同有孔虫测试的 Mg/Ca 和团块同位素测量结合起来，以产生独立的温度估计。通过结合 Mg/Ca 和簇同位素古温度方程，可以预测 Mg/Ca 和簇同位素之间的预期关系。遵守有孔虫化石中的预期关系将为古温度估计提供信心，或者，如果它们偏离预期关系，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来测试预测的关系，其覆盖的温度范围约为。 6至28度验证和校准方法。接下来，我们将使用北大西洋的一段年代明确的沉积物岩心横断面来测试该方法在末次冰期的应用。末次冰消期期间气候突变事件的严重程度仍在科学界争论中。例如，在这些极端事件期间，从海洋（约 2-4 度）和陆地（约 6-10 度）档案推断的热带降温估计存在很大差异。这种差异可能是温度代理的季节性偏差造成的。然而，热带地区平均季节温差的温度范围远大于预期。这就提出了一个问题：这些差异是真实存在的，还是由特定代理的敏感性或可靠性差异引起的。通过对镁/钙和团块同位素的串联测量，将有可能确定末次冰期气候突变事件期间温度变化的幅度并估计其空间范围。此外，已确定年代的晚第四纪岩心为我们的串联镁/钙簇同位素古温度计提供了理想的测试案例，该温度计的成功开发和应用将允许调查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

过去 42 ka 中美洲低地热带温度变化的定量估计

• DOI: 10.1016/j.epsl.2016.01.001
• 发表时间: 2016-03-15
• 期刊: Earth and Planetary Science Letters
• 影响因子: 5.3
• 作者: Anna;D. Hodell;S. Bernasconi
• 通讯作者: S. Bernasconi

Oxygen Isotopic Exchange Between CO 2 and Phosphoric Acid: Implications for the Measurement of Clumped Isotopes in Carbonates

CO 2 和磷酸之间的氧同位素交换：对碳酸盐中聚集同位素测量的影响

• DOI: http://dx.10.1029/2019gc008209
• 发表时间: 2019
• 期刊: Geochemistry, Geophysics, Geosystems
• 作者: Swart P

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

通过一致的碳酸盐标准化减少碳酸盐簇同位素分析的不确定性。

• DOI: http://dx.10.17863/cam.30392
• 发表时间: 2018
• 作者: Bernasconi S

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

有孔虫的 Mg/Ca 耦合和团簇同位素分析提供了一致的水温

• 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: S. Breitenbach;M. J. Mleneck;Anna;L. Lo;S. Bernasconi;I. Müller;J. Rolfe;F. Gázquez;M. Greaves;D. Hodell
• 通讯作者: D. Hodell

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

使用水下碳酸盐洞穴中的团簇同位素定量古含水层变化

• DOI: http://dx.10.1016/j.chemgeo.2018.05.046
• 发表时间: 2018
• 期刊: Chemical Geology
• 影响因子: 3.9
• 作者: Gázquez F