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Title: Processes affecting the cycling of iron in the Atlantic Ocean
Author: Rogan, Nicholas
ISNI:       0000 0004 5351 3010
Awarding Body: University of Liverpool
Current Institution: University of Liverpool
Date of Award: 2014
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Iron is important in determining the biogeochemistry of the oceans and has a strong control on ocean productivity. The sources of iron vary from atmospheric supply of desert dust, resuspension of oceanic sediments and fluxing of volcanic material out of vents into the deep ocean. Iron is very reactive in the water column and interacts with organic ligands, to form metal complexes, and particles via surface association. The interaction of these processes determines the ocean basin-wide distribution of total dissolved iron. Observational measurements of 234Th and 238U were used to estimate the particle scavenging fluxes of iron in the subpolar North Atlantic, resulting in mean iron losses of 1.03 ± 0.89 pM Fe d⁻¹ and 7.1 ± 5.9 pM Fe d⁺¹ between spring and summer. During the spring a volcanic eruption deposited large amounts of ash into the North Atlantic, this had a strong effect on the scavenging and fallout of iron. A novel iron model framework is presented. Diagnosis of this framework implies two important balances: • The total iron (FeT ) distribution is determined by the distribution of mixed layer preformed tracer (Fepre) and two new tracers representing sediment source and hydrothermal source, thus FeT = Fepre + Fesed + Fehyd. • Regeneration (Fereg) and scavenging (Fescav) nearly cancel each other out. Though the size of the terms are bigger than the preformed tracer they have a very limited net impact. The excess regeneration resulting from the balance of these terms, (Fereg + Fescav) indicates whether the regeneration of iron is important for setting the total dissolved iron distribution. For the majority of the ocean there is no regeneration imprint. Organic ligands play a central role in determining the dissolved iron distribution. Ligands form organic complexes with inorganic free iron and increase the solubility of iron within the water column. These organic complexes then protect the iron from scavenging. Thus, the presence of ligands enhances the transport of iron-rich water throughout the Atlantic basin.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available