Seaglider observations of biogeochemical variability in the Iberian upwelling system.

Brown, Christopher (2013) Seaglider observations of biogeochemical variability in the Iberian upwelling system. Doctoral thesis, University of East Anglia.

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Seasonal upwelling events along the Galician coastline of the North Atlantic furnish the upper
watercolumn with nutrients, resulting in strong summer phytoplankton blooms and the sustenance of
one of Europe’s largest fisheries. The episodic nature of these upwelling events result in considerable
challenges studying the region using traditional shipboard observations. This thesis demonstrates an
alternative sampling technique, providing high spatial and temporal resolution biogeochemical data
through the use of an autonomous underwater gliderthe
SG510 “Orca” was outfitted with sensors to measure dissolved oxygen, temperature,
salinity, chlorophyll a (chl a), coloured dissolved organic material (CDOM) and optical backscatter.
Deployed for 113 days over summer 2010, Orca completed 17 zonal transects across the shelf,
continental slope and open ocean at 42.1° N. Data collected during the campaign was used to
assess both the physics of the watercolumn, and the effect these physical processes have on the
region’s biogeochemistry. As part of this biogeochemical study, a novel attempt at calculating net
community production (NCP) was completed using an oxygen inventory technique.
Two major phytoplankton bloom events occurred during the deployment period, with
respective peak Chl a concentrations of 9.65 and 11.23 mg m3.
During these bloom events, NCP
varied between (net autotrophic) values of 25 and 123 (±17 ) mmol m2.
Negative values of
NCP were only observed twice for 24 and 60 hours respectively, with a maximum heterotrophy of
(±17) mmol m2
Overall, the summer season featured a net autotrophic metabolic balance of
+27 mmol m2
.thus highlighting the importance of the region for net carbon sequestration.
Finally, this thesis also demonstrates the success of using autonomous glider platforms for sustained
biogeochemical and physical observations within a highly dynamic and challenging operational
environment with strong currents and considerable shipping traffic.

Item Type: Thesis (Doctoral)
Faculty \ School: Faculty of Science > School of Environmental Sciences
Depositing User: Users 2259 not found.
Date Deposited: 13 Jun 2014 08:41
Last Modified: 13 Jun 2014 08:41


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