Watershed slope as a predictor of fluvial dissolved organic matter and nitrate concentrations across geographical space and catchment size in the Arctic

Understanding linkages between river chemistry and biological production in arctic coastal waters requires improved estimates of riverine nutrient export. Here we present the results of a synthesis effort focusing on relationships between watershed slope and seasonal concentrations of river-borne dissolved organic carbon (DOC), dissolved organic nitrogen (DON), and nitrate ( ${{{\rm{NO}}}_{3}}^{-}$ ) around the pan-Arctic. Strong negative relationships exist between watershed slope and concentrations of DOC and DON in arctic rivers. Spring and summer concentration-slope relationships for DOC and DON are qualitatively similar, although spring concentrations are higher. Relationships for ${{{\rm{NO}}}_{3}}^{-}$ are more variable, but a significant positive relationship exists between summer ${{{\rm{NO}}}_{3}}^{-}$ concentrations and watershed slopes. These results suggest that watershed slope can serve as a master variable for estimating spring and summer DOC and DON concentrations, and to a lesser degree ${{{\rm{NO}}}_{3}}^{-},$ from drainage areas where field data are lacking, thus improving our ability to develop pan-arctic estimates of watershed nutrient export.