Publication Date:
2016-01-15
Description:
The δ 30 Si of biogenic silica ( δ 30 Si 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 determine 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) the δ 30 Si BSi distribution in the surface sediment reflects the exported δ 30 Si BSi signal 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.
Print ISSN:
0886-6236
Electronic ISSN:
1944-9224
Topics:
Biology
,
Chemistry and Pharmacology
,
Geography
,
Geosciences
,
Physics
