Consequences of glacial cycles for magmatism and carbon transport at mid-ocean ridges
Consequences of glacial cycles for magmatism and carbon transport at mid-ocean ridges
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DOI：
10.1016/j.epsl.2019.115845
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发表时间：
2019-12-15
影响因子：
5.3
通讯作者：
Katz, Richard F.
中科院分区：
文献类型：
--
作者：
Cerpa, Nestor G.;Jones, David W. Rees;Katz, Richard F.
岩浆活动和火山活动将碳从固体地球转移到气候系统中。这种转移可能受到海洋和大陆冰盖之间的冰川/间冰期水循环的调节，这种循环改变了固体地球的表面负荷。由此产生的火山-碳波动被认为是更新世冰川旋回的一种调节机制。这一机制取决于海中脊对海平面变化响应的幅度和滞后。在这里，我们为这种反应开发和分析了一个新的模型，消除了以前工作中提出的一些有问题的假设。我们的模型计算了碳通量，考虑了地幔碳的热力学效应：降低固相温度和更深程度的融化。我们分析了由理想化的周期性海平面强迫的模型，并得出结论，熔融速率的波动是岩浆和碳通量的主要控制因素。我们还讨论了一个由过去800 kyr的海平面上升重建所迫的模式。表明岩浆和碳通量的峰谷变化分别达到平均通量的20%和10%左右。洋中脊排放的峰值滞后于海平面强迫的峰值不到20凯尔，而且这种滞后很可能更短。振幅和滞后对熔体偏析速率敏感。这种滞后比熔体在熔化区域垂直移动所需的时间要短得多。(C) 2019 Elsevier B.V.版权所有
Magmatism and volcanism transfer carbon from the solid Earth into the climate system. This transfer may be modulated by the glacial/interglacial cycling of water between oceans and continental ice sheets, which alters the surface loading of the solid Earth. The consequent volcanic-carbon fluctuations have been proposed as a pacing mechanism for Pleistocene glacial cycles. This mechanism is dependant on the amplitude and lag of the mid-ocean ridge response to sea-level changes. Here we develop and analyse a new model for that response, eliminating some questionable assumptions made in previous work. Our model calculates the carbon flux, accounting for the thermodynamic effect of mantle carbon: reduction of the solidus temperature and a deeper onset of melting. We analyse models forced by idealised, periodic sea level and conclude that fluctuations in melting rate are the prime control on magma and carbon flux. We also discuss a model forced by a reconstruction of eustatic sea level over the past 800 kyr. It indicates that peak-to-trough variations of magma and carbon flux are up to about 20% and 10% of the mean flux, respectively. Peaks in mid-ocean ridge emissions lag peaks in sea-level forcing by less than about 20 kyr and the lag could well be shorter. The amplitude and lag are sensitive to the rate of melt segregation. The lag is much shorter than the time it takes for melt to travel vertically across the melting region. (C) 2019 Elsevier B.V. All rights reserved.