Initial test of the silicic acid leakage hypothesis using sedimentary biomarkers

Details Initial test of the silicic acid leakage hypothesis using sedimentary biomarkers Initial test of the silicic acid leakage hypothesis using sedimentary biomarkers

Sep 2004

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2004georl..3118303h&link_type=abstract

Geophysical Research Letters, Volume 31, Issue 18, CiteID L18303

Mathematics

Logic

18

Oceanography: General: Paleoceanography, Oceanography: General: Upwelling And Convergences, Oceanography: Biological And Chemical: Biogeochemical Cycles (1615), Oceanography: Biological And Chemical: Geochemistry, Oceanography: Biological And Chemical: Stable Isotopes

Scientific paper

Several mechanisms have been proposed for large CO2 changes at glacial Terminations, including shifting the CaCO3:Corg rain ratio by changing surface water nutrient supply, altering the balance between diatom and coccolithophore production. Diatom Si:N is highest in Fe-stressed high-latitude waters. Southern Ocean Fe enrichment studies suggest diatom Si demands reduced under Fe-replete (glacial) conditions, allowing increased silicic acid to leak northward in subducted intermediate water and upwell at lower latitudes. We test this `Silicic Acid Leakage' hypothesis using relative abundances of phytoplankton-specific biomarkers in Peru margin sediments spanning 0-20 Ka. Results indicate increased coccolithophorid:diatom production from ~0.5 to 3 between 18.0-15.5 Ka. Temporal correlation with the initial pCO2 rise and early deglacial shift in mode water ventilation implicates a coincidental, possibly causative reorganization of Sub-Antarctic Mode Water formation and reduced Fe abundance. However, coccolithophorid production subsequently declined, suggesting rain ratio changes were only partly responsible for the CO2 deglacial transition.

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