Late Ordovician climate change and extinctions driven by elevated volcanic nutrient supply
Late Ordovician climate change and extinctions driven by elevated volcanic nutrient supply
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DOI：
10.1038/s41561-021-00855-5
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发表时间：
2021-12-02
影响因子：
18.3
通讯作者：
Palmer, Martin R.
中科院分区：
文献类型：
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作者：
Longman, Jack;Mills, Benjamin J. W.;Palmer, Martin R.
晚奥陶世(类似于4.59-4.44亿年前)以全球降温、冰川和严重的大灭绝为特征。这些事件可能是由营养磷(P)向海洋输送的增加和海洋生产力的相关增加推动的，但尚不清楚为什么会在地质记录中确定的两个脉冲中发生这种情况。我们通过富含营养的火山灰的海洋沉积和陆地侵位的火山灰和熔岩的风化，将这两个冷却阶段和灭绝与火山喷发联系起来。然后，我们通过将生物可利用磷供应的估计(来自枯竭和风化模型)与全球生物地球化学模型相耦合，重建了晚奥陶世火山磷输送对海洋系统的影响。我们的模型比较了蚀变前后海洋沉积物中火山灰P的含量，以确定亏损因子，并与观测到的碳同位素和重建的温度漂移进行了很好的吻合。因此，大规模火山活动可以在百万年的时间尺度上推动全球大幅降温，因为与火山沉积物的长期风化相关的磷输送，抵消了与火山喷发相关的温室气体排放的瞬时变暖。这种较长期的冷却和海洋富营养化的可能性对其他火山活动驱动的全球事件可能是重要的。
The Late Ordovician (similar to 459-444 million years ago) was characterized by global cooling, glaciation and severe mass extinction. These events may have been driven by increased delivery of the nutrient phosphorus (P) to the ocean and associated increases in marine productivity, but it is not clear why this occurred in the two pulses identified in the geological record. We link both cooling phases-and the extinction-to volcanic eruptions through marine deposition of nutrient-rich ash and the weathering of terrestrially emplaced ash and lava. We then reconstruct the influence of Late Ordovician volcanic P delivery on the marine system by coupling an estimate of bioavailable phosphate supply (derived from a depletion and weathering model) to a global biogeochemical model. Our model compares volcanic ash P content in marine sediments before and after alteration to determine depletion factors, and we find good agreement with observed carbon isotope and reconstructed temperature shifts. Hence, massive volcanism can drive substantial global cooling on million-year timescales due to P delivery associated with long-term weathering of volcanic deposits, offsetting the transient warming of greenhouse gas emission associated with volcanic eruptions. Such longer-term cooling and potential for marine eutrophication may be important for other volcanism-driven global events.