气候变化领域集成服务门户(CCPortal): Deglacial Si remobilisation from the deep-ocean reveals biogeochemical and physical controls on glacial atmospheric CO2 levels

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DOI	10.1016/j.epsl.2020.116332
	Deglacial Si remobilisation from the deep-ocean reveals biogeochemical and physical controls on glacial atmospheric CO2 levels
	Pichevin L.E.; Ganeshram R.S.; Dumont M.
发表日期	2020
ISSN	0012821X
卷号	543
英文摘要	During the last glacial period, the sluggish deep Ocean circulation sequestered carbon into the abyss leading to the lowering of atmospheric CO2. The impact of this redistribution on biologically essential nutrients remains poorly constrained. Using sedimentary δ30Si 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 CO2 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 CO2 pump and the size of the local CO2 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 CO2 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 CO2 sequestration in the abyssal ocean. The switch between the two modes of Si cycling happened at 15 ka BP, i.e. mid-deglaciation, and resulted in contrasting biological carbon drawdown responses in the EEP and globally between both phases of the deglacial CO2 rise. This illustrates that in addition to deep-sea CO2 storage and overturning, the efficiency of the biological pump also plays a crucial role in determining ocean-atmosphere CO2 exchange and shows the dual controls of ocean circulation and Fe-Si availability in this process. © 2020
关键词	Eastern Equatorial Pacific Last Deglaciation marine CO2 source marine silicon cycle
英文关键词	Carbon; Carbon dioxide; Efficiency; Feedback; Glacial geology; Iron; Iron compounds; Oceanography; Phytoplankton; Salinity measurement; Silica; Surface waters; Accumulation rates; Deep-ocean circulation; Eastern equatorial Pacific; Essential nutrients; Global ocean surface; Last glacial interglacial transitions; Last glacial period; Ocean circulation; Silicon; atmospheric chemistry; biogeochemical cycle; carbon dioxide; deep sea; deglaciation; diatom; Last Glacial; paleobiogeography; remobilization; silicon; Pacific Ocean; Pacific Ocean (Equatorial); Bacillariophyta
语种	英语
来源期刊	Earth and Planetary Science Letters
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/202833
作者单位	University of Edinburgh, Grant Institute, James Hutton Road, Edinburgh, EH9 3FE, United Kingdom; School of Earth & Environmental Sciences, Irvine Building, St Andrews, KY16 9AL, United Kingdom
推荐引用方式 GB/T 7714	Pichevin L.E.,Ganeshram R.S.,Dumont M.. Deglacial Si remobilisation from the deep-ocean reveals biogeochemical and physical controls on glacial atmospheric CO2 levels[J],2020,543.
APA	Pichevin L.E.,Ganeshram R.S.,&Dumont M..(2020).Deglacial Si remobilisation from the deep-ocean reveals biogeochemical and physical controls on glacial atmospheric CO2 levels.Earth and Planetary Science Letters,543.
MLA	Pichevin L.E.,et al."Deglacial Si remobilisation from the deep-ocean reveals biogeochemical and physical controls on glacial atmospheric CO2 levels".Earth and Planetary Science Letters 543(2020).