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

Katharine Hendry, Xun Gong, Gregor Knorr, Jennifer Pike, Ian Hall

Research output: Contribution to journalArticle (Academic Journal)peer-review

17 Citations (Scopus)
296 Downloads (Pure)

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.
Original languageEnglish
Pages (from-to)122-129
Number of pages8
JournalEarth and Planetary Science Letters
Volume438
Early online date28 Jan 2016
DOIs
Publication statusPublished - 15 Mar 2016

Keywords

  • spicule
  • silicon isotope
  • Younger Dryas
  • Heinrich Stadial
  • upwelling

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