Developing a 3.5-million-year benchmark record of Indian Ocean Dipole variability

开发印度洋偶极子变率 350 万年的基准记录

• 批准号: 447653483
• 负责人: Professorin Dr. Stefanie Kaboth-Bahr
• 金额: --
• 依托单位: Institut für Geologische Wissenschaften
• 依托单位国家: 德国
• 项目类别: Infrastructure Priority Programmes
• 财政年份: 2020
• 资助国家: 德国
• 起止时间: 2019-12-31 至 2022-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/447653483?language=en
• 关键词: Developing; 3.5; million; year; benchmark

The Indian Ocean Dipole (IOD) is the leading mode of interannual variability of sea surface temperature (SST) in the tropical Indian Ocean. The IOD describes warm (positive) and cold (negative) sea surface temperatures oscillations in the western and eastern part of the Indian ocean. The societal most relevant consequences of IOD variability range from extreme floods in eastern Africa to severe droughts in Australia. These extreme climate events caused by the IOD are predicted to become more common in the future as greenhouse gas emissions increase. Yet despite these alarming predictions and its profound impact on the bordering regions which sustain more than 2 billion people, surprisingly little is known about IOD variability in the past. In particular, the proposed sensitivity of the IOD to CO2 could be further tested if IOD variability during geological time intervals of higher CO2 contents were known. However, the insights into past IOD variability have been severely hampered by the lack of appropriate sedimentary and geochemical data sets from Indian Ocean.The here proposed research aims to elucidate IOD changes during the last 3.5 million years which coincides with distinct changes in the global CO2 level; including the mid-Pliocene warm period considered an analogue for future climate change. At the heart of this project stands the hypothesis that IOD-related SST and the associated surface wind anomalies influenced the Ekman transport of the deep meridional overturning circulation in the Indian Ocean, and thus the ventilation of the deep-water regime. Based on observational data, the weakening (strengthening) of the Ekman transport during positive (negative) IOD phases facilitates less (more) ventilation of the deep-water regime, and consequently a shoaling (deepening) of the lysocline. These new modern hydrographic findings have not yet been applied to the geological past, and thus open up an entire new avenue to research past IOP changes. Hence, this project aims to ground truth the possibility of utilizing deep-water ventilation changes in the western Indian Ocean throughout the geological past as an index of IOD variability. Two hypotheses will be specifically tackled in this project:1) Carbonate dissolution cycles as an indicator of deep-water ventilation changes in the western Indian Ocean can be used as IOD intensity index,2) The amplitude of the IOD is linear correlated to changes in global CO2 levels.To decipher its past deep-water ventilation variability in unprecedented temporal resolution, a sediment core from Site ODP 709 situated in the western equatorial Indian Ocean - a key region of IOD forcing – will be investigated utilizing a novel IOD proxy based on XRF core scanning, stable-isotope and Mg/Ca-paleothermometry based on benthic and planktic foraminifera. The synthesis of the collected data will then be used to develop a new benchmark record of IOD variability during the last 3.5 million years.

印度洋偶极子（IOD）是印度洋热带海面温度（SST）跨年度变化的领先模式。 IOD描述了印度洋西部和东部的温暖（积极）和寒冷（负）海面温度振荡。 IOD可变性的社会最相关后果范围从东非的极端楼层到澳大利亚的严重干旱。随着温室气体排放的增加，预计由IOD引起的这些极端气候事件被预计会变得更加普遍。然而，相信这些令人震惊的预测及其对维持超过20亿人口的边界地区的深远影响，过去对IOD的可变性知之甚少。特别是，如果知道较高的二氧化碳含量的地质时间间隔，则可以进一步测试IOD对CO2的敏感性。但是，由于缺乏适当的沉积和地球化学数据集，对过去的IOD变异性的见解受到了严重阻碍。在过去的350万年内，此处提出的研究旨在阐明IOD变化，这与全球CO2水平的明显变化相吻合；包括上新世温暖时期在内，这是对未来气候变化的类似物。该项目的核心表明，与IOD相关的SST和相关的表面风异常影响了印度洋深处的倾覆循环的Ekman运输，从而影响了深水状况的通风。基于观察数据，在正（负）iod阶段中，Ekman运输的弱（加强）最喜欢的（更多）对深水状态的通风，因此，裂解液的浅滩（加深）。这些新的现代水文发现尚未应用于地质的过去，因此为过去的IOP变化开辟了整个新的途径。因此，该项目的目的是将真理的可能性扎根于整个地质过去的西印度洋的深水通风变化，作为IOD变异性的指数。在该项目中将特别解决两个假设：1）碳酸盐溶解循环作为印度洋西部深水通气变化的指标，可以用作IOD强度指数，2）iod的放大器是线性的，与全球CO2级别的变化相关。西方赤道印度洋 - iod强迫的关键区域 - 将使用基于XRF核心扫描，稳定异位素和MG/CA-Paleothertotry的新型IOD代理进行研究。然后，收集到的数据的合成将用于在过去的350万年中开发新的IOD变异性基准记录。