Deglacial Si remobilisation from the deep-ocean reveals biogeochemical and physical controls on glacial atmospheric CO2 levels
Deglacial Si remobilisation from the deep-ocean reveals biogeochemical and physical controls on glacial atmospheric CO2 levels
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深海冰下硅的再活化揭示了冰川大气二氧化碳水平的生物地球化学和物理控制
DOI：
10.1016/j.epsl.2020.116332
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发表时间：
2020
影响因子：
5.3
通讯作者：
Pichevin L
中科院分区：
文献类型：
--
作者：
Pichevin L
在最后一次冰期，缓慢的深海环流将碳封存到深渊中，导致大气中二氧化碳的降低。这种重新分配对生物必需营养物质的影响仍然没有得到很好的限制。利用赤道东太平洋硅藻的沉积δ30Si和生物成因积累速率，我们提供了在最后一次冰川消融期间溶解二氧化硅和来自深海的碳重新动员的证据。由于DSi是表层海洋硅藻生长所必需的，冰期深海中DSi的浓度相当于对海洋CO2吸收的负反馈。然而，这种影响可以被冰川时期增加的铁输入所减弱，这降低了铁限制地区(如EEP)对硅藻硅的需求。我们的EEP结果表明，生物二氧化碳泵的效率和当地二氧化碳来源的大小受到上一次冰川-间冰期过渡期间铁有效性驱动的DSi利用率变化的严格控制。我们使用一个修正的Pandora盒模型来说明全球海洋表面DSi的库存是由HNLC区的Fe可获得性控制的，而不是通过上升流直接的Si供应。全新世的特点是，在铁限制和有效倾覆的条件下，生物对硅的高需求驱动了快速的硅循环模式，促进了二氧化碳的放出，并通过表面DSi的快速耗尽而产生了低效的生物C泵。在上一次冰期，由于海面富铁条件下DSi生物需要量的减少以及深海对Si和CO2的封存增加，导致海洋Si的循环变慢。这两种硅循环模式的转换发生在15ka BP，即中期冰川消融，导致了EEP和全球两个阶段的生物碳消耗响应的差异。这说明除了深海CO2的储存和倾覆外，生物泵的效率在决定海洋-大气CO2交换中也起着至关重要的作用，并显示了海洋环流和Fe-Si有效性在这一过程中的双重控制。
During the last glacial period, the sluggish deep Ocean circulation sequestered carbon into the abyss leading to the lowering of atmospheric CO 2. The impact of this redistribution on biologically essential nutrients remains poorly constrained. Using sedimentary δ 30 Si of diatoms and biogenic accumulation rates in the Eastern Equatorial Pacific (EEP), we present evidences for the remobilisation of dissolved Silica (DSi) along with carbon from the deep ocean during the Last Deglaciation. Because DSi is essential for diatoms growing in the surface ocean, its concentration in the abyss during the glacial periods amounts to a negative feedback on the oceanic CO 2 uptake. However, this effect can be muted by the increased Fe inputs during glacial periods which reduces diatom Si requirements in Fe limited regions such as the EEP. Our results from the EEP suggest that the efficiency of the biological CO 2 pump and the size of the local CO 2 source is tightly controlled by changes in DSi utilisation driven by Fe availability across the last glacial-interglacial transition. We use a modified PANDORA box model to illustrate that the inventory of DSi in the global ocean surface is controlled by Fe availability in HNLC areas rather than by straightforward Si supply though upwelling. The Holocene is characterised by a fast mode of Si cycling driven by high biological requirement for Si under conditions of iron limitation and efficient overturning, promoting CO 2 outgassing and an inefficient biological C pump via the rapid exhaustion of DSi in the surface. The last glacial period saw slower marine Si cycling as a result of decreased DSi biological requirement under Fe-replete conditions in the sea surface and increased Si and CO 2 sequestration in the abyssal ocean. The switch between the two modes of Si cycling happened at 15 ka BP, ie mid-deglaciation, and resulted in contrasting biological carbon drawdown responses in the EEP and globally between both phases of the deglacial CO 2 rise. This illustrates that in addition to deep-sea CO 2 storage and overturning, the efficiency of the biological pump also plays a crucial role in determining ocean-atmosphere CO 2 exchange and shows the dual controls of ocean circulation and Fe-Si availability in this process.
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影响因子：
4.5
作者：
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通讯作者：
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影响因子：
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DOI：
--
发表时间：
2014
期刊：
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通讯作者：
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作者：
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DOI：
--
发表时间：
1993
期刊：
影响因子：
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作者：
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通讯作者：
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