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Barium cycling in Antarctic waters: interactions with oceanic and coastal processes

Pyle, Kimberley 2016. Barium cycling in Antarctic waters: interactions with oceanic and coastal processes. PhD Thesis, Cardiff University.
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Oceanic barium has many potential proxy applications, from the quantification of export productivity using sedimentary barite, to the tracing of freshwater inputs or the circulation of deep water masses. Using these proxies to reconstruct past oceanic conditions is of particular importance in the Southern Ocean, where the ventilation of deep water masses and the biological drawdown of CO2 are thought to play a significant role in climate regulation. However, the distribution of particulate and dissolved barium in this region is not solely controlled large scale water mass circulation and predictable biological associations, but by an additional combination of spatially and temporally variable local and coastal processes. In this thesis I have found that stronger near-surface gradients are observed in Antarctic waters than in other ocean basins, with a significant association between Bad and silicic acid in surface waters at the WAP. As no direct link was observed between Bad and biological productivity, these observations can be explained by an association between Bad and siliceous detrital material, either by adsorption mechanisms or through barite precipitation in surface waters. Greater levels of Bad release and inferred barite precipitation production are observed from the decay of diatom-dominated detrital material. The accumulation of particulate barium phases in WAP shelf sediments appears to produce a benthic Bad flux that acts as a significant source of Bad to coastal waters. Sea ice is found to be a further, little studied, control on Antarctic coastal Bad distributions, with non-conservative distributions of Bad observed in sea ice cores that may be due to abiotic barite precipitation, and large fluxes of sea ice melt associated with unusually low surface Bad concentrations.

Item Type: Thesis (PhD)
Status: Unpublished
Schools: Earth and Ocean Sciences
Subjects: Q Science > QD Chemistry
Q Science > QE Geology
Date of First Compliant Deposit: 20 March 2017
Last Modified: 04 Jun 2017 09:45

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