Continuous Summer Export of Nitrogen-Rich Organic Matter from the Greenland Ice Sheet Inferred by Ultrahigh Resolution Mass Spectrometry

Runoff from glaciers and ice sheets has been acknowledged as a potential source of bioavailable dissolved organic matter (DOM) to downstream ecosystems. This source may become increasingly significant as glacial melt rates increase in response to future climate change. Recent work has identified significant concentrations of bioavailable carbon and iron in Greenland Ice Sheet (GrIS) runoff. The flux characteristics and export of N-rich DOM are poorly understood. Here, we employed electrospray ionization (ESI) coupled to Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) to determine the elemental compositions of DOM molecules in supraglacial water and subglacial runoff from a large GrIS outlet glacier. We provide the first detailed temporal analysis of the molecular composition of DOM exported over a full melt season. We find that DOM pools in supraglacial and subglacial runoff are compositionally diverse and that N-rich material is continuously exported throughout the melt season, as the snowline retreats further inland. Identification of protein-like compounds and a high proportion of N-rich DOM, accounting for 27–41% of the DOM molecules identified by ESI FT-ICR MS, may suggest a microbial provenance and high bioavailability of glacially exported DOM to downstream microbial communities

Saanich_TimeSeries_Historical_O2_DATA

Historical dissolved oxygen winkler measurements at Station S3 in Saanich Inlet from 1953 to 2007. This data includes, geographical coordinates, date (year and month), depth (meters), temperature (celcius degrees), salinity (PSU), density (sigma-theta), oxygen (milliliter per liter and micromolar). For detailed methods see the manuscript

Saanich_TimeSeries_Chemical

Chemical bottle data collected from Station S3 (-123.505, 48.59166667) in Saanich Inlet, BC, Canada. This data includes unique geographical coordinates for sampling station (Decimal degrees), Numerical identifier of individual cruises (Numeric string), Date of cruise (YY-MM-DD), Sampling depth (Meters), Oxygen concentration calculated from CTD SBE (Micromolar), Phosphate (Bran Luebbe AutoAnalyser - colorimetric) (Micromolar), Silicate (Bran Luebbe AutoAnalyser - colorimetric) (Micromolar), Nitrate (Bran Luebbe AutoAnalyser - colorimetric) (Micromolar), Average Ammonium (fluorometric) (Micromolar), Average Nitrite (colorimetric) (Micromolar), Average Hydrogen sulfide (colorimetric) (Micromolar), Cell counts value quantified by flow cytometry (Number of cells per millilitre (cells/mL)), Average concentration of Nitrogen gas (headspace) (Micromolar), Standard deviation for Nitrogen gas, Average concentration of Oxygen (headspace) (Micromolar), Standard deviation for Oxygen, Average concentration of Carbon dioxide (headspace) (Micromolar), Standard deviation for Carbon dioxide, Average concentration of Nitrous oxide (headspace or automated purge-and-trap) (Micromolar), Standard deviation for Nitrous oxide, Average concentration of Methane (headspace or automated purge-and-trap) (Nanomolar), Standard deviation for Methane. For detailed description of methods see manuscript

Saanich_TimeSeries_CTD_DATA

CTD data from Station S3 in Saanich Inlet. This data includes unique geographical coordinates for sampling station (Decimal degrees), Numerical identifier of individual cruises (Numeric string), Date of cruise (YY-MM-DD), CTD pressure measurement in intervals of 1 meter (Decibars), CTD temperature (Celsius degrees), CTD conductivity (Millisiemens per centimetre), CTD fluorometer chlorophyll measurement (Chlorophyll concentration in milligram per cubic meter), CTD transmissometer measurement (Light transmission), CTD Photosintentically active radiation (PAR) measurement (Irradiance), CTD Dissolved oxygen sensor measurement (SBE) (Volts), Oxygen concentration based on CTD Oxygen SBE (Micromolar), CTD salinity measurement at each pressure point (Practical salinity unit), CTD density measurement at each pressure point (Sigma-theta). For detailed description on methods see manuscript

Saanich_TimeSeries_Winkler_DATA

Dissolved oxygen winkler measurements at Station S3 in Saanich Inlet from 2008-2014. This data includes unique geographical coordinates, date (year and month), depth (meters) and oxygen concentration (micromolar). See manuscript for detailed methods