A scientist from the International Arctic Research Center/University of Alaska Fairbanks seeks to understand the biogeochemical processes governing the composition, reactivity, transformation and flux of organic carbon species, including dissolved, colloidal and particulate organic carbon from the Yukon River Basin. Being heavily influenced by ice, snow and permafrost dynamics, the Yukon River Basin, a pristine river basin, is sensitive to environmental and climate change. With up to 50% of the world's soil organic carbon stored in the northern region, the role of arctic/subarctic rivers in the remobilization of organic carbon and thus marine and global carbon cycles is far more important than previously recognized. Due to the Yukon River's remoteness and the extreme weather conditions, the composition and reactivity of organic carbon species entering the ocean via the Yukon remain largely unknown and the riverine carbon export flux is poorly quantified. Observations will include phase partitioning of organic carbon between dissolved, colloidal and particulate phases, and concentrations, optical properties, molecular and isotopic (d13C, d15N and ?14C) composition and reactivity of size fractionated organic carbon. Field and laboratory experiments will also be carried out to examine the extent to which organic carbon fractionates during ice formation and how the fractionation drives carbon partitioning and transformation. This project will be among the first to combine both molecular-level and basin-scale observations to understand temporal and spatial variations in composition and flux of organic carbon species in a large but pristine and less anthropogenically influenced river basin. The proposed research will provide valuable data for comparative studies between drainage basins, and provide inputs for and contribute effectively to the integrated carbon cycle program and model development, and the understanding of the environmental impacts from a changing climate.
