| Summary: | In the past decade there has been an overall decrease in Arctic Ocean sea ice cover. Changes to the ice cover have important consequences for organic carbon cycling, especially over the continental shelves. When sea ice is formed, dissolved organic carbon (DOC) and other tracers are fractionated in relation to the initial water. Two separate “freeze-out” experiments were conducted to observe the effects of fractionation during ice formation. In experiment 1, marine and freshwater end members were mixed together in different ratios to create four different salinities. In experiment 2, a brackish water sample was collected. The initial unfrozen water, ice melt, and post-freeze brine water were tested for dissolved organic carbon, total nitrogen (TN), dissolved inorganic carbon (DIC), fluorescence and absorption (optics), water isotopes (δ18O and δD), and lignin phenols. Results showed a clear fractionation effect for all parameters, where the ice samples contained much less of the dissolved species than the enriched brine samples. This information is important to consider when trying using these parameters to determine the fate of carbon and the freshwater budget to the Arctic Ocean.
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