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高校地质学报 ›› 2025, Vol. 31 ›› Issue (03): 275-285.DOI: 10.16108/j.issn1006-7493.2024041

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古气候数据同化重建早始新世气候适宜期全球海水表面温度

张昊勋,李明松*   

  1. 北京大学 地球与空间科学学院 造山带与地壳演化教育部重点实验室,北京 100871
  • 出版日期:2025-06-17 发布日期:2025-06-17

Reconstruction of Global Sea Surface Temperatures during the Early Eocene Climatic Optimum Using Paleoclimate Data Assimilation

ZHANG Haoxun,LI Mingsong*   

  1. Key Laboratory of Orogenic Belts and Crustal Evolution, Ministry of Education, School of Earth and Space Sciences, Peking University, Beijing 100871, China
  • Online:2025-06-17 Published:2025-06-17

摘要: 早始新世气候适宜期(EECO,53.26~49.14 Ma)全球温度在百万年尺度上达到最高值,是66 Ma以来最温暖的时期,是政府间气候变化委员会(IPCC)第六次评估报告最极端的共享经济路径情景SSP8.5未来全球温度的地质参考时期。前人利用地球系统模式和古气候替代指标,对EECO全球海水表面温度状态进行了重建。然而,地球系统模式的边界条件往往缺乏约束,难以重建准确的EECO全球海水表面温度状态;古气候替代指标重建结果之间存在分歧、且具有全球耦合性差等不足。该研究利用新兴的古气候数据同化技术,开展中等复杂程度地球系统模式cGENIE模拟,考虑大气二氧化碳浓度、碱度和雨比率三种不确定性因素,以100个模拟试验结果作为先验估计,融合了35个大洋钻探点位的三种古海水温度指标,即TEX86、浮游有孔虫Mg/Ca 和δ18O,高精度地重建了EECO时期全球耦合的海水表面温度。数据同化得到的全球海水表面温度为30.7 ℃(95%置信区间为28.8~33.0 ℃),同化结果具有全球耦合的特点,与地球系统模式模拟的先验值相比精度显著提高。开展了敏感性实验,证实不同替代指标类型对数据同化重建结果有显著的影响,去除TEX86指标数据同化得到的海水表面温度偏冷,而去除δ18O指标的同化结果则偏热。本研究对EECO热室时期开展高精度的全球海水表面温度重建,为未来气候变化的这一关键地质参考型提供了更为精确的约束。

关键词: 古气候数据同化, 早始新世气候适宜期, 海水表面温度, 古气候替代指标, 地球系统模式

Abstract: The Early Eocene Climatic Optimum (EECO, 53.26-49.14 Ma) represents the warmest period of the past 66 million years, with global temperatures reaching their highest levels on a million-year scale. This period serves as a geological reference for future Earth temperatures under the most extreme Shared Socioeconomic Pathways (SSP8.5) scenario in the Sixth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC). Previous studies have reconstructed the global sea surface temperature (SST) state of the EECO using Earth system models and paleoclimate proxies. However, Earth system models often lack constraints on boundary conditions, making it difficult to accurately reconstruct the global SST state of the EECO. Additionally, there are discrepancies between different proxy reconstruction results. This study utilizes an emerging paleoclimate data assimilation approach, conducting simulations with the Earth system model of intermediate complexity, cGENIE. Our 100-member ensemble considers three most important uncertainties: atmospheric carbon dioxide concentration, alkalinity, and rain ratio. We assimilate three types of paleotemperature proxies (TEX86, Mg/Ca and δ18O of planktonic foraminifera) from 35 ocean drilling sites to reconstruct high-precision, globally coupled SSTs during the EECO. The data assimilation yielded a global SST of 30.7 ℃ (95% confidence interval: 28.8-33.0 ℃ ), characterized by significantly improved accuracy compared to prior estimates from Earth system model simulations. Sensitivity experiments confirmed that different types of proxies have a significant impact on the data assimilation reconstruction results: SSTs reconstructed without TEX86 proxy data were lower than those assimilating all proxies, while those without δ18O data were higher. This study provides a high-precision reconstruction of globally coupled SSTs during the EECO hothouse period, offering an accurate geological reference for future climate change.

Key words: paleoclimate data assimilation, Early Eocene Climate Optimum, sea surface temperature, paleoclimate proxies, Earth
system models

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