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A switch from Si(OH) 4 to NO 3 − depletion in the glacial Southern Ocean
Author(s) -
Brzezinski Mark A.,
Pride Carol J.,
Franck Valerie M.,
Sigman Daniel M.,
Sarmiento Jorge L.,
Matsumoto Katsumi,
Gruber Nicolas,
Rau Greg H.,
Coale Kenneth H.
Publication year - 2002
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 - 10.1029/2001gl014349
Subject(s) - glacial period , geology , silicic acid , oceanography , diatom , subtropics , latitude , organic matter , atmospheric sciences , chemistry , paleontology , ecology , biology , geodesy , organic chemistry
Phytoplankton in the Antarctic deplete silicic acid (Si(OH) 4 ) to a far greater extent than they do nitrate (NO 3 − ). This pattern can be reversed by the addition of iron which dramatically lowers diatom Si(OH) 4 :NO 3 − uptake ratios. Higher iron supply during glacial times would thus drive the Antarctic towards NO 3 − depletion with excess Si(OH) 4 remaining in surface waters. New δ 30 Si and δ 15 N records from Antarctic sediments confirm diminished Si(OH) 4 use and enhanced NO 3 − depletion during the last three glaciations. The present low‐Si(OH) 4 water is transported northward to at least the subtropics. We postulate that the glacial high‐Si(OH) 4 water similarly may have been transported to the subtropics and beyond. This input of Si(OH) 4 may have caused diatoms to displace coccolithophores at low latitudes, weakening the carbonate pump and increasing the depth of organic matter remineralization. These effects may have lowered glacial atmospheric pCO 2 by as much as 60 ppm.