CoolRhythms: the impact of ice volume and ocean circulation on Earth's Coolhouse climate beat

地球不断变化的气候与其从太阳获得的能量有着千丝万缕的联系，这种能量受地球轨道的偏心、倾角和进动的驱动而有节奏地变化。地球重新分配这种太阳能，维持着持续数百万年的冷热气候状态(迈尔)。地球长期气候状态之间的变化是由极地冰和温室气体的巨大变化引起的。在过去的4000万年里，冰量在影响地球气候方面发挥了重要作用。其中一种气候状态--酷宅--捕捉到了大冰盖最初在地球两极形成的时间。太阳能还推动了更快的气候响应，这与这些轨道变化保持一致。尽管驱动地球气候反应的有节奏的能量没有改变，但地球的气候变化本身并没有随着时间的推移而稳定下来。我们目前还不清楚是什么原因造成了这种情况。通过CoolRhythms的提议，我将确定地球气候中这些不同的节拍发生的时间和原因，并探索全球变暖是否会在未来导致另一次气候节拍的变化。两个主要的冰层增长事件恰逢酷宅一词开始和中期的重大转变。令人惊讶的是，在这两个重要的气候转变期间，地球的气候节拍做出了不同的反应。大约34年前，在早期的Coolhouse，当地球从温暖的气候转变为凉爽的气候时，冰首次在南极的冰上形成，偏心率作为地球气候变化的主要驱动力没有改变。地球在15到5月前的中期再次冷却，并在15到5月前增加了更多的冰，但这一次气候节拍从偏心变成了倾斜。为什么地球的气候改变了它的节拍是一个谜，我将从以下几个方面进行调查：1.确定地球在Coolhouse转变早期和中期的确切气候节拍；2.确定哪些过程导致地球的气候节拍从偏心转变为倾斜；3.探索未来变暖是否会逆转这种转变。CoolRhythms将在伦敦大学学院与世界专家网络合作主办。为了实现我的目标，我将把数据科学与一种新的定向采样方法结合起来，这种方法整合了地层学和地球化学，以优化信息恢复。我将用来自深海微化石的新数据来填补我们知识中的空白，并通过解决对现有记录的相互冲突的解释，来确定地球气候在关键转变中的节拍。我将开发软件来描述不同记录中的气候节拍，然后将它们结合起来，获得气候的全球观点。我将分析在IODP海洋钻探探险期间在所有大洋盆地收集的深海沉积物微化石的稳定氧碳同位素和微量元素组成。我将把这种地球化学与沉积成分结合起来，以重建与地球气候节拍相同规模的高分辨率冰量和海洋环流模式。我还将使用模型来测试冰增长的位置如何影响气候节拍，以及偏心率驱动的节拍是否会在未来重新出现。我的方法将使我能够确定在这些转变期间，是哪个地球系统的反馈导致了不同的气候节拍。完善我们对地球气候如何在变暖和变冷的气候状态下变化的理解，最终将有助于理解地球变暖可能如何影响未来气候的可变性。

Earth's changing climate is inexorably linked to the energy it receives from the Sun, which varies rhythmically, driven by the eccentricity, obliquity and precession of Earth's orbit. Earth redistributes this solar energy, sustaining warmer and cooler climate states that last for millions of years (Myr). The shifts between Earth's long-term climate states are caused by large changes in polar ice and greenhouse gasses. Over the last 40 million years, ice volume has played an important role in influencing Earth's climate. One of these climate states - the Coolhouse - captures when large ice sheets first formed at Earth's poles. The solar energy also drives a faster climate response, which beats in tune with these orbital variations. Even though the rhythmic energy that drives Earth's climate response has not changed, Earth's climate beat itself has not been stable through time. We currently do not understand what causes this. Through the CoolRhythms proposal, I will establish when and why these different beats in Earth's climate occur and explore if global warming could cause another change of climate beat in the future.Two major ice growth events coincide with big transitions at the beginning and the middle of the Coolhouse word. Surprisingly, Earth's climate beat responded differently during these two important climatic transitions. About 34 Myr ago in the early Coolhouse, ice first formed on Antarctic ice as Earth shifted from a warm to cool climate transition and eccentricity was unchanged as the main driver of Earth's climate beat. The Earth cooled again in the mid-Coolhouse and gained more ice between 15 and 5 Myr ago, yet this time the climate beat changed from eccentricity to obliquity. Why Earth's climate changed its beat is an enigma, which I will investigate by:1. Establishing Earth's exact climate beat during the early and mid-Coolhouse transitions; 2. Determining which processes caused Earth's climate beat to switch from eccentricity to obliquity; 3. Exploring if future warming could reverse this switch. CoolRhythms will be hosted at UCL in collaboration with a network of world experts. To achieve my aims, I will combine data science with a novel targeted sampling approach that integrates stratigraphy and geochemistry to optimise information recovery. I will establish Earth's climate beat across the key transitions by filling gaps in our knowledge with new data from deep-sea microfossils and by resolving conflicting interpretations of existing records. I will develop software to characterise the climatic beat in the different records and then combine them to acquire a global view of climate. I will analyse the stable oxygen and carbon isotope and trace element composition of microfossils from deep-sea sediments, collected during IODP ocean drilling expeditions in all ocean basins. I will combine this geochemistry with the sedimentary composition to reconstruct high-resolution ice volume and ocean circulation patterns at the same scale as Earth's climate beat. I will also use modelling to test how the location of the ice growth affects the climate beat and whether an eccentricity driven beat could return in the future.My approach will enable me to determine which Earth system feedback caused the differing climate beats during these transitions. Refining our understanding of how Earth's climate beat varied during warmer and cooler climate states will ultimately help understand how a warmer Earth may affect the variability of future climate.