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Studies on trace metal dynamics in mesoscale anticyclonic eddies in the Gulf of Alaska Crispo, Sabrina Marie

Abstract

Haida eddies are large, anticyclonic eddies that form off the coast of the Queen Charlotte Islands, British Columbia during the winter. They can transport up to 6000km³ of coastal water offshore annually. The eddy can retain its coastal signature for up to 3 years before it dissipates. Due to the length of time these eddies exist and their minimal interactions with surroundings, the Haida eddies are an ideal laboratory in which to study processes affecting trace metal distributions as coastal water ages. Haida eddies were found to transport high concentrations of dissolved aluminum and manganese into the Gulf of Alaska. Average dissolved aluminum and manganese concentrations decreased within the eddy as it aged. The quantity of dissolved aluminum these eddies supply to the Gulf of Alaska was similar to the predicted amount of dissolved aluminum supplied by dust deposition to this region. Average dissolved cadmium and copper concentrations increased within the eddy as it traveled offshore into waters with higher nutrient concentrations. For both cadmium and copper, the increase in the amount of the dissolved metal concentration within the core of the eddy over time was not significantly different from the amount predicted by physical mixing. The processes controlling dissolved iron distributions within the surface waters of the Haida eddy over time were also studied with the aid of tracers. It was found that both biological uptake and particle scavenging played a role in dissolved iron removal. Dissolved manganese supplied information on external dissolved iron inputs, although removals of dissolved manganese and dissolved iron were not correlated. Changes in cadmium to phosphate ratios support the theory of preferential cadmium uptake in iron-limited waters, and the similarities between iron and copper dynamics in the surface waters suggest that the biological uptake and regeneration of copper and iron are linked.

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