Digging into Eocene hothouse climate variability: Elemental signals derived from X-ray fluorescence scanning of Messel sediment cores

由于温室气体浓度上升，世界变暖，地球系统走向前所未有的气候状态，挑战社会适应。然而，地球的历史为未来几十年全球变暖提供了可能的类比。其中包括始新世早期（~50 Ma）的气候状态，根据目前的温室气体排放轨迹，可能在2150年达到。因此，对始新世气候和生态系统的研究可以提供对它们可能在不久的将来对应的状态和动态的关键见解。这样的“过去的教训”可以帮助微调模型预测，并最终支持我们适应未来的能力。位于德国西南部达姆施塔特附近的联合国教科文组织世界遗产梅塞尔化石坑的马尔湖沉积物为研究始新世早期至中期气候变化提供了一个特殊的沉积档案。虽然梅塞尔以其保存完好的动物和植物遗迹而闻名，为古近纪的陆地生态系统提供了难得的一瞥，但它的沉积物代表了一个独特的档案，记录了地球在地质上最近的温室时期（约48 Ma）的短期气候动态。以前的研究已经证明了这种沉积档案在轨道时间尺度上对气候变化的敏感性（例如，通过花粉分析）。由于在梅塞尔（Messel）恢复的沉积物（很可能）呈现出年度层压，它们进一步允许深入了解短期（即十年至潜在的季节性）气候变化，因为存在极高分辨率的代理数据。然而，对其地球化学变化的分析尚无法提供更高时间分辨率的见解。在这里，我们建议通过Messel FB2001钻孔岩心的高分辨率（1毫米= ~7年）XRF岩心扫描生成地球化学数据，以破译始新世温室世界中欧的水文变化。这些数据有可能在前所未有的年代际到亚轨道时间和时间分辨率上深入了解梅塞尔的古环境和古气候演变。因此，新的数据将用于构建一个高分辨率，天文调谐的年龄模型，改进目前基于低分辨率花粉数据的年龄模型。我们将进一步开发一个干湿指数，用于解释(i)在类似未来全球变暖情景的条件下的气候趋势和动态，以及（ii）限制气候对进化模式的影响，这些影响是由Messel发现的独特化石记录所揭示的。

As the world warms due to rising greenhouse gas concentrations, the Earth system moves toward climate states without historic precedent, challenging societal adaptation. However, Earth’s history offers possible analogues for the warming world of the coming decades. These include the climatic state of the early Eocene (~50 Ma), which based on current greenhouse-gas emission trajectories, will likely be reached by 2150. Hence, the study of Eocene climates and ecosystems can provide critical insight into the states and dynamics of their likely near-future counterparts. Such a ‘lesson from the past’ can be instrumental for fine-tuning model predictions and ultimately support our abilities for adaption to the future.An exceptional sedimentary archive to study early to middle Eocene climate variability is presented by the maar-lake sediments of the Messel fossil-pit, UNESCO world heritage site located near Darmstadt, SW Germany. While Messel is famous for its exceptionally well-preserved faunal and floral remains that provide a rare look into terrestrial ecosystems of the Paleogene, its sediments represent a unique archive for short-term climate dynamics operating during the geologically most recent greenhouse period of the Earth at around 48 Ma. Previous studies have demonstrated the sensitivity of this sedimentary archive to climate changes (e.g., via pollen analysis) on orbital time scales. As the sediments recovered at Messel exhibit (most likely) annual lamination, they further allow for insights into short-term (i.e. decadal down to potentially seasonal) climate variability, given the presence of extremely highly resolved proxy data.However, analysis of its geochemical changes allowing insights in much higher temporal resolution are yet unavailable. Here we propose to generate geochemical data via high-resolution (1 mm = ~7 yr) XRF core scanning of the Messel FB2001 drill core to decipher the hydrological variability in Central Europe during the Eocene greenhouse world. Such data have the potential to yield insight into the paleoenvironmental and paleoclimatic evolution of Messel in unprecedented decadal to sub-orbital time temporal resolution. As such, the new data will be used to construct a high-resolution, astronomically tuned age model, improving the present age model that is based on low-resolution pollen data. We will further develop a wet-dry index that will be utilized to decipher (i) climate trends and dynamics under conditions resembling those expected during future global warming scenarios and (ii) constraining the climatic impact on evolutionary patterns as revealed by the unique fossil record recovered at Messel.