Deglacial diatom production in the tropical North Atlantic driven by enhanced silicic acid supply

Hendry, Katharine R., Gong, Xun ORCID: https://orcid.org/0000-0001-9308-4431, Knorr, Gregor, Pike, Jennifer ORCID: https://orcid.org/0000-0001-9415-6003 and Hall, Ian R. ORCID: https://orcid.org/0000-0001-6960-1419 2016. Deglacial diatom production in the tropical North Atlantic driven by enhanced silicic acid supply. Earth and Planetary Science Letters 438 , pp. 122-129. 10.1016/j.epsl.2016.01.016

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Abstract

Major shifts in ocean circulation are thought to be responsible for abrupt changes in temperature and atmospheric CO2 during the last deglaciation, linked to variability in meridional heat transport and deep ocean carbon storage. There is also widespread evidence for shifts in biological production during these times of deglacial CO2 rise, including enhanced diatom production in regions such as the tropical Atlantic. However, it remains unclear as to whether this diatom production was driven by enhanced wind-driven upwelling or density-driven vertical mixing, or by elevated thermocline concentrations of silicic acid supplied to the surface at a constant rate. Here, we demonstrate that silicic acid supply at depth in the NE Atlantic was enhanced during the abrupt climate events of the deglaciation. We use marine sediment archives to show that an increase in diatom production during abrupt climate shifts could only occur in regions of the NE Atlantic where the deep supply of silicic acid could reach the surface. The associated changes are indicative of enhanced regional wind-driven upwelling and/or weakened stratification due to circulation changes during phases of weakened Atlantic meridional overturning. Globally near-synchronous pulses of diatom production and enhanced thermocline concentrations of silicic acid suggest that widespread deglacial surface-driven breakdown of stratification, linked to changes in atmospheric circulation, had major consequences for biological productivity and carbon cycling.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Earth and Environmental Sciences
Subjects:	Q Science > QE Geology
Publisher:	Elsevier
ISSN:	0012-821X
Funders:	NERC
Date of Acceptance:	16 January 2016
Last Modified:	31 Oct 2022 10:43
URI:	https://orca.cardiff.ac.uk/id/eprint/85898

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