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它从太阳接收的能量有着不可分割的联系，而太阳的能量是有节奏地变化的，这是由地球轨道的偏心率、倾角和进动所驱动的。地球重新分配了这些太阳能，维持了数百万年的温暖和寒冷的气候状态（Myr）。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——冷库——记录了地球两极大冰原最初形成的时间。太阳能还推动了更快的气候反应，与这些轨道变化步调一致。即使驱动地球气候反应的有节奏的能量没有改变，地球的气候节奏本身也没有随着时间的推移而稳定。我们目前还不知道是什么原因造成的。通过coolrhythm的提议，我将确定这些不同的地球气候节奏发生的时间和原因，并探索全球变暖是否会在未来引起另一种气候节奏的变化。两个主要的冰生长事件与库尔库斯世界的开始和中期的大转变相吻合。令人惊讶的是，在这两次重要的气候转变中，地球的气候变化反应不同。大约34万年前，在早期的冷库时期，随着地球气候从温暖转变为凉爽，偏心率作为地球气候变化的主要驱动力没有改变，冰首先在南极冰上形成。地球在中间冷库再次冷却，并在15至5亿年前获得了更多的冰，但这一次气候变化从偏心率变为倾角。为什么地球的气候会改变它的节奏是一个谜，我将通过：在冷库转换的早期和中期建立地球确切的气候节奏；2. 确定是哪些过程导致地球的气候变化从偏心率转变为倾角；3. 探索未来的变暖是否会逆转这种转变。coolrhythm将在伦敦大学学院与世界专家网络合作举办。为了实现我的目标，我将把数据科学与一种新的目标采样方法结合起来，该方法将地层学和地球化学相结合，以优化信息恢复。我将用深海微化石的新数据填补我们知识上的空白，并解决对现有记录的相互矛盾的解释，从而在关键的过渡时期建立地球的气候节奏。我将开发软件来描述不同记录中的气候变化特征，然后将它们结合起来，以获得全球气候的观点。我将分析从深海沉积物中收集的微化石的稳定氧、碳同位素和微量元素组成，这些化石是在IODP海洋钻探考察期间在所有海洋盆地收集的。我将把这个地球化学与沉积成分结合起来，以与地球气候变化相同的尺度重建高分辨率的冰量和海洋环流模式。我还将使用模型来测试冰生长的位置如何影响气候变化，以及未来是否会出现偏心驱动的气候变化。我的方法将使我能够确定哪些地球系统反馈导致了这些转变期间不同的气候变化。完善我们对地球气候在温暖和寒冷的气候状态下如何变化的理解，最终将有助于理解地球变暖如何影响未来气候的变化。

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.