High export of nitrogen and dissolved organic carbon from an Alpine glacier (Indren Glacier, NW Italian Alps)

Mountain glaciers can export large amounts of nitrogen (N) and carbon (C) to downstream aquatic ecosystems. To date, however, the number of studies that analysed concentrations and fluxes of N forms and dissolved organic carbon (DOC) from glaciers in the European Alps and worldwide is limited, given the high complexity of data gathering in harsh high-elevation environments. In this work, we rely upon new, unexploited data from field campaigns pursued during 2012-2015 at high elevations (> 3000 m a.s.l.) of the Indren Glacier (NW Italian Alps) to (1) develop glacio-hydrological modelling and stream flow estimates within a heavily glacier-fed catchment, (2) provide N forms and DOC concentrations and estimated fluxes in meltwater, and (3) provide possible explanations of cryospheric control upon water chemistry. Water and soil samples were also collected at two lower-elevation sites along the glacial stream to investigate the downstream variability of N forms and DOC. Nitrate-N, dissolved organic nitrogen, and DOC concentrations (0.21 ± 0.12, 0.19 ± 0.14, 1.16 ± 0.63 mg L-1, respectively) and yields (220, 210, 1279 kg km-2 year-1, respectively) were among the highest considering other glaciated areas of the globe, probably due to high atmospheric N and C depositions. Limited effect of soil on water characteristics was found and attributed to the reduced soil development in recently deglaciated areas (after the Little Ice Age), thus underlining the role of glacier melting in determining N and C dynamics in high-elevation, Alpine surface waters.