Seasonal changes in the optical properties of dissolved organic matter (DOM) in large Arctic rivers

Arctic rivers deliver over 10% of the annual global river discharge yet little is known about the seasonal fluctuations in the quantity and quality of terrigenous dissolved organic matter (tDOM). A good constraint on such fluctuations is paramount to understand the role that climate change may have on tDOM input to the Arctic Ocean. To understand such changes the optical properties of colored tDOM (tCDOM) were studied. Samples were collected over several seasonal cycles from the six largest Arctic Rivers as part of the PARTNERS project. This unique dataset is the first of its kind capturing seasonal trends in Arctic river tCDOM composition. Parallel Factor Analysis was used to decompose the combined tCDOM fluorescence signal into five independent model components. The relationship of individual fluorescence components to dissolved organic carbon, lignin phenol concentrations, and the 14C-DOC age were explored. This study demonstrates the usefulness and limits of CDOM as a proxy to understand seasonal and longer term changes in the quantity and quality of Arctic river tDOM