Oceanography Seminar

February 20, 3:00pm - 4:15pm
Mānoa Campus, MSB 100

Sally Walker
Post-doctorate Fellow
Dalhousie University

“Fluorescent Dissolved Organize Matter (FDOM) in the Arctic Ocean and its Surrounding Watersheds”

Abstract: Given the pace of climate change, it is important to better understand dissolved organic matter (DOM) storage and cycling in high latitude rivers and its subsequent export to the Arctic Ocean. In conjunction, a good constraint on the nature and distributions of freshwater inputs to the Arctic Ocean is paramount to understand the role climate change may play for the Arctic's hydrological cycle. To address these concerns the optical properties of fluorescent DOM (FDOM) and colored DOM (CDOM) were studied in five large Arctic rivers over two seasonal cycles, within the Canadian Archipelago, and across the Arctic Basin. Excitation/Emission Matrix spectroscopy and Parallel Factor Analysis (PARAFAC) coupled with optical indices were used to characterize the DOM. In comparing Pan-Arctic relationships between the optical properties and chemical properties of DOM in large Arctic rivers, FDOM could be used as a potential indicator to discriminate between relatively fresh terrestrial DOM sources from terrestrial DOM that has recently been altered by microbes. Differences in FDOM character between the rivers could be explained by general watershed characteristics, including vegetation, topography, and hydrology. Based on these differences, it is possible that increased hydrological connectivity in the Ob catchment and the abundance of lakes within the Mackenzie watershed may influence FDOM concentrations and the microbial processing of DOM within these watersheds. In surface waters of the Canadian Archipelago, 17 % of the DOM pool was of a terrestrial origin, even though waters were diluted with sea ice melt, suggesting the likelihood of a subsurface plume of tDOM entrained within river runoff from Arctic Rivers. In the interior Arctic, an elevated terrestrial FDOM signal in the Eurasian Basin points to the presence of Eurasian river FDOM entrained within river runoff in the Transpolar Drift. In contrast, autochthonous/microbial FDOM sources were more important the Canadian Basin and the terrestrial FDOM signal was much lower relative to the Eurasian Basin. This study illustrates the usefulness of FDOM to finger-print water masses within the Arctic Ocean and shows promise to improve our understanding of upper Arctic Ocean ventilation patterns.

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