近日，美国犹他大学Harper Dustin T.团队，在研究古新世晚期和始新世早期海面温度和大气CO₂的长期和短期耦合中取得新进展。该研究于2024年8月26日发表于国际一流学术期刊《美国科学院院刊》上。

据了解，古新世晚期和始新世早期(LPEE)的特征是存在长期的(百万年，Myr)全球变暖，和短暂的、突然的(千年，kyr)变暖事件，被称为极热。虽然两者都被归因于温室效应(CO₂)的作用力，但气候的长期趋势可能受到其他作用力因素(即构造)的影响，大气CO₂驱动变暖的程度仍不清楚。

本研究使用了一套新的和现有的，来自太平洋钻井计划站点1209和1210收集的浮游有孔虫观测数据，反演了一个多代理贝叶斯分层模型，以量化Myr间隔内的海表温度(SST)和大气CO₂。该重建跨越了长期LPEE变暖(约58 Ma)的开始，以及两个最大的古近纪极热活动，古新世—始新世极热(PETM，约56Ma)和始新世极热2 (ETM-2，约54 Ma)。

研究结果显示，长期(LPEE)和短期(PETM和ETM-2)的CO₂和温度在之间存在很强的耦合，但在两个时间尺度上具有不同的太平洋气候敏感性。综合CO₂和碳同位素综合趋势表明，PETM和ETM-2中驱动CO₂增加的碳源可能是产甲烷、有机或混合的，而δ¹³C值较高的碳源(如火山脱气)与长期LPEE有关。重建的PETM (5,800Gt C)和ETM-2 (3,800Gt C)的排放与未来排放情景的质量相当，这强调了这些事件作为人为变化模拟的价值。

附：英文原文

Title: Long- and short-term coupling of sea surface temperature and atmospheric CO2 during the late Paleocene and early Eocene

Author: Harper, Dustin T., Hnisch, Brbel, Bowen, Gabriel J., Zeebe, Richard E., Haynes, Laura L., Penman, Donald E., Zachos, James C.

Issue&Volume: 2024-8-26

Abstract: The late Paleocene and early Eocene (LPEE) are characterized by long-term (million years, Myr) global warming and by transient, abrupt (kiloyears, kyr) warming events, termed hyperthermals. Although both have been attributed to greenhouse (CO₂) forcing, the longer-term trend in climate was likely influenced by additional forcing factors (i.e., tectonics) and the extent to which warming was driven by atmospheric CO₂ remains unclear. Here, we use a suite of new and existing observations from planktic foraminifera collected at Pacific Ocean Drilling Program Sites 1209 and 1210 and inversion of a multiproxy Bayesian hierarchical model to quantify sea surface temperature (SST) and atmospheric CO₂ over a 6-Myr interval. Our reconstructions span the initiation of long-term LPEE warming (~58 Ma), and the two largest Paleogene hyperthermals, the Paleocene–Eocene Thermal Maximum (PETM, ~56 Ma) and Eocene Thermal Maximum 2 (ETM-2, ~54 Ma). Our results show strong coupling between CO₂ and temperature over the long- (LPEE) and short-term (PETM and ETM-2) but differing Pacific climate sensitivities over the two timescales. Combined CO₂ and carbon isotope trends imply the carbon source driving CO₂ increase was likely methanogenic, organic, or mixed for the PETM and organic for ETM-2, whereas a source with higher δ¹³C values (e.g., volcanic degassing) is associated with the long-term LPEE. Reconstructed emissions for the PETM (5,800 Gt C) and ETM-2 (3,800 Gt C) are comparable in mass to future emission scenarios, reinforcing the value of these events as analogs of anthropogenic change.

DOI: 10.1073/pnas.2318779121

Source: https://www.pnas.org/doi/abs/10.1073/pnas.2318779121