Redox-controlled carbon and phosphorus burial: A mechanism for enhanced organic carbon sequestration during the PETM
Redox-controlled carbon and phosphorus burial: A mechanism for enhanced organic carbon sequestration during the PETM
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DOI：
10.1016/j.epsl.2017.09.011
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发表时间：
2017-12
影响因子：
5.3
通讯作者：
N. Komar;R. Zeebe
中科院分区：
文献类型：
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作者：
N. Komar;R. Zeebe
地质记录显示，在古新世-始新世最热时期(PETm，∼56 Ma)，碳循环发生了重大扰动，其标志是全球变暖超过5°C，海洋领域的碳同位素负漂移至少为2.5‰。整个事件持续了大约20万年，与数千年来向海洋-大气系统释放大量轻碳有关。在这里，我们关注的是PETM的末期阶段，在此阶段，海洋-大气系统迅速从碳循环扰动中恢复过来。我们使用碳循环箱模型来研究大规模二氧化碳释放事件(如PETM)期间表层海洋生物生产、碳、氧、磷和碳酸盐化学之间的反馈。模型结果表明，氧化还原控制的碳磷反馈能够在较大的碳排放事件中产生增强的有机碳固存。碳氧化的地点(海洋和大气)不会影响碳封存的数量。然而，尽管该模型得到了与氧、有机碳过量积累速率(恢复阶段的∼1700pgC)、出口产量和δ13C数据一致的趋势，但它未能再现恢复阶段沉积物碳酸盐含量的变化幅度和CCD超加深。在恢复阶段，CCD值和沉积物碳酸盐含量超调被预计的CaCO3降雨增加所抑制。尽管如此，有迹象表明，在PETM期间，CaCO3出口保持相对稳定。如果这是真的，那么最初3,000 pg C的脉冲，然后是2,500 pg C的额外缓慢泄漏，可能会引发向表层海洋的营养物质加速供应，从而促进有机碳的输出，从而增加有机碳的固存，导致在PETM终止阶段加速恢复海洋-大气生物地球化学。
Geological records reveal a major perturbation in carbon cycling during the Paleocene–Eocene Thermal Maximum (PETM,∼ 56 Ma), marked by global warming of more than 5° C and a prominent negative carbon isotope excursion of at least 2.5‰ within the marine realm. The entire event lasted about 200,000 yr and was associated with a massive release of light carbon into the ocean–atmosphere system over several thousands of years. Here we focus on the terminal stage of the PETM, during which the ocean–atmosphere system rapidly recovered from the carbon cycle perturbation. We employ a carbon-cycle box model to examine the feedbacks between surface ocean biological production, carbon, oxygen, phosphorus, and carbonate chemistry during massive CO 2 release events, such as the PETM. The model results indicate that the redox-controlled carbon–phosphorus feedback is capable of producing enhanced organic carbon sequestration during large carbon emission events. The locale of carbon oxidation (ocean vs. atmosphere) does not affect the amount of carbon sequestered. However, even though the model produces trends consistent with oxygen, excess accumulation rates of organic carbon (∼ 1700 Pg C during the recovery stage), export production and δ 13 C data, it fails to reproduce the magnitude of change of sediment carbonate content and the CCD over-deepening during the recovery stage. The CCD and sediment carbonate content overshoot during the recovery stage is muted by a predicted increase in CaCO 3 rain. Nonetheless, there are indications that the CaCO 3 export remained relatively constant during the PETM. If this was indeed true, then an initial pulse of 3,000 Pg C followed by an additional, slow leak of 2,500 Pg C could have triggered an accelerated nutrient supply to the surface ocean instigating enhanced organic carbon export, consequently increasing organic carbon sequestration, resulting in an accelerated restoration of ocean–atmosphere biogeochemistry during the termination phase of the PETM.