Enhanced clay formation key in sustaining the Middle Eocene Climatic Optimum.
Enhanced clay formation key in sustaining the Middle Eocene Climatic Optimum.
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DOI：
10.1038/s41561-023-01234-y
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发表时间：
2023
影响因子：
18.3
通讯作者：
von Strandmann, Philip A. E. Pogge
中科院分区：
文献类型：
--
作者：
Krause, Alexander J. J.;Sluijs, Appy;van der Ploeg, Robin;Lenton, Timothy M.;von Strandmann, Philip A. E. Pogge
始新世中期气候最佳（大约4000万年前）是一个大约40万年的全球变暖阶段，与大气中二氧化碳浓度的增加和深海酸化有关，这中断了始新世的长期冷却趋势。与始新世早期的全球变暖阶段相比，这种异常漫长的持续时间令人困惑，因为依赖温度的硅酸盐风化应该提供了负反馈，在这个时间尺度上吸收了二氧化碳。在这里，我们通过测量锂同位素比率（报告为δ7Li）来研究这次气候变暖事件中的硅酸盐风化作用，锂同位素比率是一种来自一套富含碳酸盐的开放海洋沉积物的硅酸盐风化过程的示踪剂。我们发现δ7Li的正偏移值为~3‰，这是迄今为止唯一发现的与变暖事件有关的偏移值。箱形模型模拟支持这一信号，反映了全球从具有次生矿物溶解的一致风化向具有次生矿物形成的不一致风化的转变。我们推测，在气候最佳之前，大陆有相当大的土壤屏蔽。大陆火山活动的增加引发了变暖事件，但粘土形成的增加维持了这一事件，粘土形成隔绝了形成碳酸盐的阳离子，缩短了碳酸盐-硅酸盐循环。粘土矿物动态可能在中间（即10万年）时间框架内发生的气候事件的碳循环中发挥重要作用。根据海洋碳酸盐的锂同位素记录，与其他始新世短暂变暖事件相比，中始新世气候最佳期持续时间较长，可以用硅酸盐矿物风化形成粘土的增加来解释。
The Middle Eocene Climatic Optimum (around 40 million years ago) was a roughly 400,000-year-long global warming phase associated with an increase in atmospheric CO2 concentrations and deep-ocean acidification that interrupted the Eocene’s long-term cooling trend. The unusually long duration, compared with early Eocene global warming phases, is puzzling as temperature-dependent silicate weathering should have provided a negative feedback, drawing down CO2 over this timescale. Here we investigate silicate weathering during this climate warming event by measuring lithium isotope ratios (reported as δ7Li), which are a tracer for silicate weathering processes, from a suite of open-ocean carbonate-rich sediments. We find a positive δ7Li excursion—the only one identified for a warming event so far —of ~3‰. Box model simulations support this signal to reflect a global shift from congruent weathering, with secondary mineral dissolution, to incongruent weathering, with secondary mineral formation. We surmise that, before the climatic optimum, there was considerable soil shielding of the continents. An increase in continental volcanism initiated the warming event, but it was sustained by an increase in clay formation, which sequestered carbonate-forming cations, short-circuiting the carbonate–silicate cycle. Clay mineral dynamics may play an important role in the carbon cycle for climatic events occurring over intermediate (i.e., 100,000 year) timeframes. The long duration of the Middle Eocene Climatic Optimum, compared with other transient Eocene warming events, can be explained by an increase in clays forming from the weathering of silicate minerals, according to lithium isotope records of marine carbonates.
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DOI：
10.1073/pnas.2111332119
发表时间：
2022-03-15
影响因子：
11.1
作者：
Gaskell DE;Huber M;O'Brien CL;Inglis GN;Acosta RP;Poulsen CJ;Hull PM
通讯作者：
Hull PM
影响因子：
5.9
作者：
Fernández DA;Palazzesi L;González Estebenet MS;Tellería MC;Barreda VD
通讯作者：
Barreda VD
影响因子：
64.8
作者：
Cramwinckel, Margot J.;Huber, Matthew;Sluijs, Appy
通讯作者：
Sluijs, Appy
影响因子：
4.3
作者：
Cramwinckel, Margot J.;Woelders, Lineke;Bijl, Peter K.
通讯作者：
Bijl, Peter K.
影响因子：
56.9
作者：
Bijl, Peter K.;Houben, Alexander J. P.;Brinkhuis, Henk
通讯作者：
Brinkhuis, Henk