Synthesis of Fluvial Dissolved Organic Matter and Inorganic Nitrogen Data Across Space and Scale in the Arctic: Circumpolar Truths and Regional Distinctions

Arctic river biogeochemistry has been studied at a variety of locations and scales to improve understanding of land-ocean connectivity and establish baselines for assessing climate change impacts. A synthesis of water chemistry data from studies conducted in northern Alaska and other locations around the pan-Arctic domain reveals strong negative relationships between concentrations of dissolved organic matter (DOC and DON) and watershed slope that hold up across a wide range of scales and geographic regions. Patterns for dissolved inorganic nitrogen (DIN) are more variable, but there is also a significant positive relationship between nitrate concentration and watershed slope. These patterns in DOM and nitrate generally reflect differences in proportional contributions of coastal plain versus mountainous terrain among drainage basins, and are more specifically related to differences in organic matter content of soils in these contrasting terrains. Differences in water residence times that likely correlate with watershed slope may also contribute to the observed patterns. In any case, it appears that watershed slope serves as a master variable for estimating DOC, DON, and nitrate concentrations in Arctic rivers. These relationships provide a tool for estimating fluvial DOM and nitrate concentrations for drainage areas where field data are lacking, and thus improve our ability to develop pan-Arctic estimates of watershed export.