Evidence for a biological pump driver of atmospheric CO2 rise during Heinrich Stadial 1

The initial trigger of the atmospheric CO2 rise during Heinrich Stadial 1 (HS1: 14.5–17.5 kyr B.P.) remains elusive. We present a compilation of four paired surface and intermediate‐depth foraminiferal δ13C records to test whether reduced biological pump efficiency led to the initial CO2 rise during...

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Bibliographic Details
Published inGeophysical research letters Vol. 43; no. 23; pp. 12,242 - 12,251
Main Authors Hertzberg, Jennifer E., Lund, David C., Schmittner, Andreas, Skrivanek, Alexandra L.
Format Journal Article
LanguageEnglish
Published Washington John Wiley & Sons, Inc 16.12.2016
Subjects
AMOC
Atlantic Meridional Overturning Circulation (AMOC)
biological pump
Carbon dioxide
Carbon dioxide atmospheric concentrations
Circulation
CO2
Deglaciation
Depth
Efficiency
foraminifera
Geophysics
Greenhouse gases
Heinrich Stadial 1
Meltwater
Meteorology
Mineral nutrients
Nitrogen
Nutrients
Ocean-atmosphere interaction
Plankton
Remineralization
Temperature (air-sea)
Upper ocean
Younger Dryas
δ13C
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Summary:The initial trigger of the atmospheric CO2 rise during Heinrich Stadial 1 (HS1: 14.5–17.5 kyr B.P.) remains elusive. We present a compilation of four paired surface and intermediate‐depth foraminiferal δ13C records to test whether reduced biological pump efficiency led to the initial CO2 rise during the last deglaciation. Surface ocean δ13C decreased across HS1 while intermediate‐depth δ13C increased, leading to a reduction in the upper ocean δ13C gradient. Our compilation also suggests the δ13C gradient increased during the Bølling‐Allerød (12.9–14.5 kyr B.P.) and decreased during the Younger Dryas (YD: 11.7–12.9 kyr B.P.). The HS1 and YD data are consistent with reduced biological export of isotopically light carbon from the surface ocean and its remineralization at depth. Our results support the idea that a weaker Atlantic Meridional Overturning Circulation decreased biological pump efficiency by increasing the overall fraction of preformed nutrients in the global ocean, leading to an increase in atmospheric CO2. Key Points Decreased surface‐intermediate ocean δ13C gradients suggest that the biological pump weakened during HS1 and the YD Weakened AMOC during HS1 likely altered the global nutrient budget, decreased biological pump efficiency, and led to CO2 rise Proxy records are inconsistent with entrainment of light carbon in AAIW/SAMW during HS1
ISSN:0094-8276
1944-8007
DOI:10.1002/2016GL070723