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Controls on biogenic silica burial in the Southern Ocean


Chase, Z and Kohfeld, KE and Matsumoto, K, Controls on biogenic silica burial in the Southern Ocean, Global Biogeochemical Cycles, 29, (10) pp. 1599-1616. ISSN 0886-6236 (2015) [Refereed Article]


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Copyright 2015 American Geophysical Union.

DOI: doi:10.1002/2015GB005186


Understanding the controls on opal export in the Southern Ocean can inform both the prediction of how the leakage of silicic acid from the Southern Ocean responds to climate and the interpretation of paleo-proxies. We have compiled a database of 185 230Thorium-normalized opal burial rates and 493 opal concentration measurements in Southern Ocean sediments and matched these with environmental climatologies. By subdividing the Southern Ocean on the basis of oceanographic regions and interpolating the opal burial rates, we estimate a total biogenic Si burial south of 40S of 2.3  1.0 Tmol Si yr−1. In both the seasonally ice-covered and permanently ice-free regions we can explain 73% of opal burial variability from surface ocean properties. Where sea ice is present for at least part of the year, the length of the ice-free season determines the upper limit of opal burial in the underlying sediments. In the ice-free regions of the Southern Ocean, the supply of silicic acid through winter mixing is the most important factor. Our results do not support a strong role of iron in controlling opal burial. We do however find that satellite-derived net primary production increases with increasing (modeled) dust delivery. These findings support the decoupling between carbon and opal fluxes in the Southern Ocean. When corrected for opal dissolution, the observed opal fluxes are in reasonable agreement with fluxes simulated using an ocean biogeochemical model. However, the results suggest current preservation algorithms for opal could be improved by incorporating the composition of particle flux, not only its magnitude.

Item Details

Item Type:Refereed Article
Keywords:Southern Ocean, opal, silicic acid, sea ice, iron, thorium-230
Research Division:Earth Sciences
Research Group:Oceanography
Research Field:Chemical oceanography
Objective Division:Expanding Knowledge
Objective Group:Expanding knowledge
Objective Field:Expanding knowledge in the earth sciences
UTAS Author:Chase, Z (Professor Zanna Chase)
ID Code:103451
Year Published:2015
Funding Support:Australian Research Council (FT120100759)
Web of Science® Times Cited:28
Deposited By:IMAS Research and Education Centre
Deposited On:2015-10-11
Last Modified:2017-10-31
Downloads:212 View Download Statistics

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