北京大学李明松团队报道了5600万年前发生的，古新世—始新世极热事件对海洋化学的影响，该项研究定量重建了过去海洋pH值的下降幅度、碳酸盐饱和度的降低程度以及大气CO2浓度的升高幅度。2024年11月12日，国际知名学术期刊《自然—地球科学》发表了这一成果。
据介绍，古新世—始新世热极大期是5600万年前的一个气候事件，其特征是碳的快速释放和广泛的海洋酸化。然而，人们对酸化和海洋饱和状态演变的理解仍然受到相当大的不确定性的阻碍，主要源于代理数据的有限可用性。在这种条件下，数据同化可以对这一时期的大气CO2变化、海洋酸化和碳酸盐饱和状态进行内部一致的评估。
通过同化海底沉积物CaCO3和海表温度代用数据，结合地球系统模型（包括一个综合碳酸盐系统）的模拟，重建了古新世—始新世热极大碳循环扰动。重建显示，大气中的CO2含量从890PPM(95%可信区间：680-1,170ppm) 升到1,980PPM（1，680-2,280ppm），pH值（0.46单位，范围从0.31-0.63单位），地表水方解石饱和状态显著下降，从事件前的10.2（7.5-12.8）下降到极热期间的3.8（2.8-5.1）。在古新世—始新世极热期，高纬度地表水碳酸盐欠饱和现象显著加剧，与当前因人为CO2排放导致的北极文石饱和度下降的趋势相平行。
附：英文原文
Title: Coupled decline in ocean pH and carbonate saturation during the Palaeocene–Eocene Thermal Maximum
Author: Li, Mingsong, Kump, Lee R., Ridgwell, Andy, Tierney, Jessica E., Hakim, Gregory J., Malevich, Steven B., Poulsen, Christopher J., Tardif, Robert, Zhang, Haoxun, Zhu, Jiang
Issue&Volume: 2024-11-12
Abstract: The Palaeocene–Eocene Thermal Maximum, a climate event 56 million years ago, was characterized by rapid carbon release and extensive ocean acidification. However, our understanding of acidification and the evolution of ocean saturation states continues to be hindered by considerable uncertainties, primarily stemming from the limited availability of proxy data. Under such conditions, data assimilation allows for an internally consistent assessment of atmospheric CO2 changes, ocean acidification and carbonate saturation state during this period. Here, we present a reconstruction of the Palaeocene–Eocene Thermal Maximum carbon cycle perturbation by assimilating seafloor sediment CaCO3 and sea surface temperature proxy data with simulations from an Earth system model, which includes a comprehensive carbonate system. Our reconstructions indicate a substantial increase in atmospheric CO2 from 890ppm (95% credible interval: 680–1,170ppm) to 1,980ppm (1,680–2,280ppm), coupled with a notable decline in pH (0.46 units, ranging from 0.31 to 0.63 units) and surface-water calcite saturation state, decreasing from 10.2 (7.5–12.8) in the pre-event period to 3.8 (2.8–5.1) during the thermal maximum. Carbonate undersaturation intensified substantially in high-latitude surface waters during the Palaeocene–Eocene Thermal Maximum, paralleling the current decline in Arctic aragonite saturation driven by anthropogenic CO2 emissions.
DOI: 10.1038/s41561-024-01579-y
Source: https://www.nature.com/articles/s41561-024-01579-y