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Simulating the modern δ 30 Si distribution in the oceans and in marine sediments
Author(s) -
Gao S.,
WolfGladrow D. A.,
Völker C.
Publication year - 2016
Publication title -
global biogeochemical cycles
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.512
H-Index - 187
eISSN - 1944-9224
pISSN - 0886-6236
DOI - 10.1002/2015gb005189
Subject(s) - silicic acid , biogenic silica , photic zone , sediment , oceanography , sedimentary rock , geology , diatom , fractionation , environmental science , mineralogy , geochemistry , paleontology , phytoplankton , chemistry , nutrient , organic chemistry
The δ 30 Si of biogenic silica ( δ 30Si BSi ) in marine sediments is a promising proxy for the reconstruction of silicic acid utilization by diatoms in the geological past. The application of this proxy, however, requires an understanding of the modern δ 30 Si distributions and their controlling mechanisms. Here we present results from a modern climate simulation with a coupled ocean‐sediment model that includes a prognostic formulation of biogenic silica production with concurrent silicon isotopic fractionation. In agreement with previous studies, biological fractionation combined with physical transport and mixing determines the oceanic distribution of simulated δ 30 Si. A new finding is a distinct seasonal cycle of δ 30 Si in the surface ocean, which is inversely related to that of silicic acid concentration and mixed layer depth. We also provide the first simulation results of sedimentary δ 30 Si, which reveal that (1) theδ 30Si BSidistribution in the surface sediment reflects the exportedδ 30Si BSisignal from the euphotic zone and (2) the dissolution of biogenic silica in the sediment acts as a source of relatively light δ 30 Si into the bottom waters of the polar oceans, while it is a source of heavier δ 30 Si to the subtropical South Atlantic and South Pacific.