Sedimentary opal records in the eastern equatorial Pacific: It is not all about leakage ...

• Main Authors: Calvert, Stephen E., Francois, Roger
• Format: Text
• Language: English
• Published: American Geophysical Union 2017
• Subjects: Southern Ocean
• Online Access: https://dx.doi.org/10.14288/1.0078404; https://doi.library.ubc.ca/10.14288/1.0078404

The clear predictions of the silicic acid leakage hypothesis (SALH) resulted in a number of studies of downcore opal records from the tropical Pacific. The original SALH predicts that unused silicic acid, due to Fe-driven changes in Si versus N limitation, escaped from the glacial Southern Ocean to equatorial upwelling regimes where it enhanced diatom productivity, thereby decreasing coccolith growth and lowering atmospheric CO2. In contrast to SALH predictions, however, sedimentary records from the eastern equatorial Pacific (EEP) do not show enhanced opal burial during the Last Glacial Maximum (LGM) but higher rates of opal burial during the deglaciation and marine isotopic stage 3 (MIS3). The peak in opal productivity during the deglaciation has been attributed to increased supply of nutrient-rich waters driven by stronger upwelling of deep water in the Southern Ocean at the end of last glacial period. The large peak in opal burial observed in a number of EEP cores during MIS3 was interpreted as evidence ...