Biogeochemical cycling of dissolved and particulate manganese in the northeast Pacific and Canadian western Arctic

• Main Author: Sim, Nari
• Format: Thesis
• Language: English
• Published: University of British Columbia 2018
• Subjects: Arctic; Arctic Ocean; Pacific; Beaufort Sea; Sea ice; Subarctic
• Online Access: http://hdl.handle.net/2429/67889

The biogeochemical cycling of manganese (Mn) in the ocean is regulated by the complex interaction between external sources, removal processes and its redox sensitive chemistry. The goal of this research was to expand our knowledge about the relative importance of each process, to assess the major controls on annual variability in Mn distributions, and to explore interaction between particulate and dissolved phases of Mn. To address these questions, the distribution of suspended particulate Mn (pMn) and dissolved Mn (dMn) in the northeast Pacific Ocean across the Line-P transect and the Beaufort Sea of the Arctic Ocean was evaluated in the context of the regional physical and chemical processes. Within the Summer Mixing Layer (SML) of the Line-P transect, it was found that eolian dust input and photo-reduction elevate dMn and the annual variability in dMn at the station nearest the shore is driven by variations in the strength of Ekman transport, which brings Mn-rich coastal water to this area. Below the SML, where UV ration is no longer available for photo-reduction, rapid oxidation is identified as the main process responsible for elevated pMn. Based on a simple advection/mixing model, it was identified that the horizontal distribution of dMn at intermediate depths is influenced either by eastward advection of NPIW or by northward advection of low dMn water, depending on the position of the boundary between the Pacific subarctic and subtropical gyres. Within the Oxygen Minimum Zone (OMZ), Mn is regulated by increased reduction across the transect. The decreasing concentration of dMn from the continent to the open ocean, and the low lithogenic pMn near the continental margin in the OMZ, are the combined result of reduction of re-suspended particles and addition of dMn from the sediments. This work also evaluated the biogeochemical cycling of dMn in the Beaufort Sea. Mn in this area is controlled more by external sources rather than internal cycling. River water, sea ice melt water, and photo-reduction dominate in the surface, while advection of water mass and the mixing with remobilized dMn from the continental margin are the dominant influences at the mid-depth in this region. Science, Faculty of Earth, Ocean and Atmospheric Sciences, Department of Graduate