A multi-proxy approach to decipher global sea-level and ice-volume dynamics during late Cenozoic “snapshot” intervals based on benthic foraminiferal calcite from ODP Site 849

人类对地球气候的影响越来越大，导致全球变暖，从而导致极地冰盖融化和全球海平面上升。为了保护沿海地区在未来变暖的情况下不受海平面上升的影响，需要准确预测未来的海平面变化。因此，该项目旨在更好地了解比今天更温暖的世界中的海平面和冰量动态。为此，将重建过去500万年地球历史上六个关键的冰川-间冰期周期的海平面/冰量变化(海洋同位素阶段(MIS1-5、MIS29-31、MIS57-59、MIS99-101、MISM1-MG1和MISCN5-CN7))。这些晚新生代的“快照”间隔在全球冰量方面产生了截然不同的背景条件，但包括在轨道构型、大气温室气体浓度和/或温度方面与变暖未来非常相似的阶段。拟议的研究将基于对从赤道东太平洋(海洋钻探方案第849号地点)钻探岩心中发现的保存完好的海底有孔虫进行的地球化学分析。更准确地说，氧同位素分析将与从镁/钙和“聚集同位素”得出的深海温度相结合，以得出海水的氧同位素组成，这是全球冰量和海平面变化的替代指标。这种多指标方法包括两个独立的古温度计(镁/钙和“簇状同位素”)，以测试从氧同位素提取的温度信号的准确性，从而得出海平面变化。因此，与以往的海平面重建技术相比，这是向前迈出的关键一步，并可能有助于解决晚新生代海平面记录中的不一致之处，因为这些记录尚可获得。最后，将为该项目的晚新生代“快照”间隔生成的记录将揭示低频(冰期-间冰期)海平面/冰量变化，但也将揭示与人类相关的时间尺度的高频变化。因此，该项目将提供进一步的线索，以实现对全球海平面/冰量动态的全面机械性(冰期-间冰期至千年尺度)的理解，这些动态与近期全球变暖的总体背景有关。

The increasing influence of humans on Earth's climate causes global warming and hence melting of polar ice sheets and a rise in global sea levels. To protect coastal regions from rising seas in a warming future, accurate projection of future sea-level change is needed. Therefore, this project aims to better understand sea-level and ice-volume dynamics in a world that is warmer-than-today. For this purpose, sea-level/ice-volume change will be reconstructed for six critical glacial-interglacial cycles from the past 5 million years of Earth’s history (Marine Isotope Stages (MIS) 1–5, MIS 29–31, MIS 57–59, MIS 99–101, MIS M1–MG1, and MIS CN5–CN7). These late Cenozoic “snapshot” intervals yield decisively different background conditions in terms of global ice volume, but include phases that represent close analogues to a warming future with regard to orbital configuration, atmospheric greenhouse-gas concentration and/or temperature. The proposed study will be based on the geochemical analysis of well-preserved benthic foraminifera retrieved from a drill core in the Eastern Equatorial Pacific Ocean (Ocean Drilling Program Site 849). More precisely, oxygen-isotope analysis will be combined with Mg/Ca- and “clumped-isotope”-derived deep-sea temperatures to yield the oxygen-isotope composition of seawater, which is a proxy for global ice-volume and hence sea-level change. This multi-proxy approach includes two independent paleothermometers (Mg/Ca and “clumped isotopes”) to test the accuracy of the temperature signal extracted from oxygen isotopes to derive sea-level change. It therefore represents a critical step forward with respect to previous sea-level reconstruction techniques and will likely help to resolve inconsistencies in late Cenozoic sea-level records as they are yet available. Finally, records to be generated for the individual late Cenozoic “snapshot” intervals of this project will reveal both low-frequency (glacial-interglacial) sea-level/ice-volume changes, but also high-frequency variabilities connected to human-relevant timescales. The project will thus provide further clues to achieve a full mechanistic (glacial-interglacial to millennial-scale) understanding of global sea-level/ice-volume dynamics relevant within the overall context of near-future warming.