同济大学黄恩清团队近日的研究揭示了中新世气候最佳条件下构造脱气能加速海洋碳循环。这一研究成果发表在2024年1月2日出版的国际学术期刊《科学通报》上。

研究人员通过对全球海洋新发布的高分辨率底栖有孔虫氧(δ¹⁸O)和碳(δ¹³C)同位素记录的时间演化相分析发现，在MCO期间，海洋碳循环的变化导致了40.5万年的气候-冰冻圈系统(δ¹³C-主导-δ¹⁸O)的偏心率变化。这与先前报道的渐新世至中新世(约3,400-600万年前)大部分时期的气候—主导—碳(δ¹⁸O-主导-δ¹³C)情景形成对比。

进一步的敏感性分析和模型模拟表明，大气CO₂浓度升高及其产生的温室效应加强了MCO期间的低纬度水文循环，加速了海洋碳循环对偏心率作用力的响应。当地球气候处于温暖状态时，热带气候过程在调节碳循环变化方面发挥了更重要的作用，这与上新世—更新世(约600万年前)期间，极地冰盖动力学的主导影响相反。

据介绍，中新世气候最佳期(MCO，约1700-1400万年前)的全球变暖与洪水玄武岩火山活动和海洋地壳活动产生的大量碳排放有关。然而，构造碳脱气对气候变化与碳循环相互作用的扰动尚不清楚。

附：英文原文

Title: Accelerated marine carbon cycling forced by tectonic degassing over the Miocene Climate Optimum

Author: Fenghao Liu, Jinlong Du, Enqing Huang, Wentao Ma, Xiaolin Ma, Lucas J. Lourens, Jun Tian

Issue&Volume: 2024/01/02

Abstract: Global warming during the Miocene Climate Optimum (MCO, ～17-14 million years ago) is associated with massive carbon emissions sourced from the flood basalt volcanism and ocean crustal production. However, the perturbation of tectonic carbon degassing on the interaction between climate change and carbon cycle remains unclear. Here, through time-evolutive phase analysis of new and published high-resolution benthic foraminiferal oxygen (δ¹⁸O) and carbon (δ¹³C) isotope records from the global ocean, we find that variations in the marine carbon cycle lead the climate-cryosphere system (δ¹³C-lead-δ¹⁸O) on 405,000-year eccentricity timescales during the MCO. This is in contrast to the previously reported climate-lead-carbon (δ¹³C-lead-δ¹⁸O) scenario during most of the Oligo-Miocene (～34–6 million years ago). Further sensitivity analysis and model simulations suggest that the elevated atmospheric CO₂ concentrations and the resulting greenhouse effect strengthened the low-latitude hydrological cycle during the MCO, accelerating the response of marine carbon cycle to eccentricity forcing. Tropical climate processes played a more important role in regulating carbon-cycle variations when Earth’s climate was in a warm regime, as opposed to the dominant influence of polar ice-sheet dynamics during the Plio-Pleistocene (after ～6 million years ago).

DOI: 10.1016/j.scib.2023.12.052

Source: https://www.sciencedirect.com/science/article/abs/pii/S2095927323009386