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New insights into processes controlling the δ30Si of sinking diatoms: a seasonally resolved box model approach

Citation

Closset, I and Cardinal, D and Trull, TW and Fripiat, F, New insights into processes controlling the δ30Si of sinking diatoms: a seasonally resolved box model approach, Global Biogeochemical Cycles, 33, (8) pp. 957-970. ISSN 0886-6236 (2019) [Refereed Article]

Copyright Statement

Copyright 2019 American Geophysical Union

DOI: doi:10.1029/2018GB006115

Abstract

In the Southern Ocean, the silicon (Si) biogeochemical cycle is dominated by processes such as the supply of Si into the surface waters, Si uptake into diatom frustules, and their subsequent dissolution and export. Due to the incomplete assimilation of the silicic acid pool (DSi) and isotopic fractionation during silicification, the Si isotopic composition (δ30Si) of biogenic silica (BSi) is closely linked to the degree of Si utilization in the mixed layer (ML). In this study, we combined modelling approaches and seasonal sediment trap records of δ30Si of exported BSi to investigate the magnitude, timing, and isotopic composition of the flux of siliceous particles transferred from the surface to the deep ocean. We implemented a box model to describe the temporal evolution of DSi and BSi concentrations and δ30Si in the ML and at depth. The model allows us to quantify fluxes of Si in and out of the ML associated with export, dissolution, and mixing. It highlights that the time‐integrated δ30Si of exported BSi measured in the sediments reflects the extent of DSi consumption at the time when net BSi production and diatom accumulation are maximal in the ML and confirms that the δ30Si of diatoms is a reliable proxy for past Si utilization.

Item Details

Item Type:Refereed Article
Keywords:silicon isotopes, Southern Ocean, model, silicon cycle, diatoms, export production
Research Division:Earth Sciences
Research Group:Oceanography
Research Field:Chemical oceanography
Objective Division:Environmental Management
Objective Group:Management of Antarctic and Southern Ocean environments
Objective Field:Antarctic and Southern Ocean oceanic processes
UTAS Author:Trull, TW (Professor Thomas Trull)
ID Code:139513
Year Published:2019
Deposited By:CRC-Antarctic Climate & Ecosystems
Deposited On:2020-06-18
Last Modified:2020-07-22
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