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Initial test of the silicic acid leakage hypothesis using sedimentary biomarkers
Author(s) -
Higginson Matthew J.,
Altabet Mark A.
Publication year - 2004
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2004gl020511
Subject(s) - diatom , oceanography , silicic acid , geology , bloom , environmental science
Several mechanisms have been proposed for large CO 2 changes at glacial Terminations, including shifting the CaCO 3 :C org 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 p CO 2 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 CO 2 deglacial transition.