Abstract
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.
Original language | English |
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Article number | 116332 |
Journal | Earth and Planetary Science Letters |
Volume | 543 |
Early online date | 28 May 2020 |
DOIs | |
Publication status | Published - 1 Aug 2020 |
Keywords
- marine silicon cycle
- Last Deglaciation
- marine CO source
- Eastern Equatorial Pacific