Investigating the controls on surface ocean dimethyl sulphide concentrations at regional to global scales
This thesis details a series of investigations into the controls on surface ocean concentrations of the climatically relevant, biogenic sulphur compound, dimethyl sulphide (DMS) at regional to global scales. The primary focus is upon the role of solar irradiance and metrics of biological activity in...
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| Format: | Thesis |
| Language: | English |
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2012
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| Online Access: | https://ueaeprints.uea.ac.uk/id/eprint/43162/ https://ueaeprints.uea.ac.uk/id/eprint/43162/1/2012MilesCJPhD.pdf |
| Summary: | This thesis details a series of investigations into the controls on surface ocean concentrations of the climatically relevant, biogenic sulphur compound, dimethyl sulphide (DMS) at regional to global scales. The primary focus is upon the role of solar irradiance and metrics of biological activity in modulating DMS concentrations using bivariate and multivariate statistical techniques in conjunction with three different data sets from multiple spatial and temporal scales. Firstly, a statistical investigation into the proposed strong positive relationship between surface DMS concentration and the average mixed layer irradiance (solar radiation dose: SRD) was undertaken using DMS data from a series of cruise tracks from the Atlantic Meridional Transect (AMT) programme, primarily from the oligotrophic Atlantic gyres. Positive correlations were found between DMS and (a) SRD formulations using concurrently sampled in situ data (ρ=0.55 n=65 p<0.01), (b) SRD formulations based on using climatological data (ρ=0.74 n=65 p<0.01) and (c) a ultraviolet radiation dose (ρ= 0.67 n=54 p<0.01). The next analysis investigated whether the inclusion of a biological variable (chlorophyll or primary production) alongside irradiance could explain additional variance in DMS concentrations. This analysis employed a database of cruise data from a range of biogeochemical domains, latitudes and trophic conditions (AMT, the Barents Sea, the Atmospheric Chemistry Studies in the Oceanic Environment (ACSOE) research campaign and the DImethyl Sulphide biogeochemistry within a COccolithophore bloom (DISCO) study. Using multiple linear regression (MLR) analyses, it was found that the combination of, in situ rate of primary production and underwater irradiance accounted for significant variance in DMS concentrations in data from discrete depths within the euphotic zone (R2 = 0.55), from near-surface waters (R2 = 0.66) and within depth profile integrated data (R2 = 0.40). The final analysis is an investigation into global surface DMS ... |
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