Suspended sediment in a high-Arctic river:an appraisal of flux estimation methods

• Published in: Science of The Total Environment
• Main Authors: Ladegaard-Pedersen, Pernille, Sigsgaard, Charlotte, Kroon, Aart, Abermann, Jakob, Skov, Kirstine, Elberling, Bo
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2017
• Subjects: Annual suspended sediment flux; Arctic river discharge; Estimation methods; Extreme events; Q/h relation; Arctic; Greenland; Zackenberg
• Online Access: https://curis.ku.dk/portal/da/publications/suspended-sediment-in-a-higharctic-river(804a2bc0-eb96-42c5-b690-f482d6c546c7).html; https://doi.org/10.1016/j.scitotenv.2016.12.006

Quantifying fluxes of water, sediment and dissolved compounds through Arctic rivers is important for linking the glacial, terrestrial and marine ecosystems and to quantify the impact of a warming climate. The quantification of fluxes is not trivial. This study uses a 8-years data set (2005-2012) of daily measurements from the high-Artic Zackenberg River in Northeast Greenland to estimate annual suspended sediment fluxes based on four commonly used methods: M1) is the discharge weighted mean and uses direct measurements, while M2-M4) are one uncorrected and two bias corrected rating curves extrapolating a continuous concentration trace from measured values. All methods are tested on complete and reduced datasets. The average annual runoff in the period 2005-2012 was 190±25mio·m 3 y -1 . The different estimation methods gave a range of average annual suspended sediment fluxes between 43,000±10,000ty -1 and 61,000±16,000ty -1 . Extreme events with high discharges had a mean duration of 1day. The average suspended sediment flux during extreme events was 17,000±5000ty -1 , which constitutes a year-to-year variation of 20-37% of the total annual flux. The most accurate sampling strategy was bi-daily sampling together with a sampling frequency of 2h during extreme events. The most consistent estimation method was an uncorrected rating curve of bi-daily measurements (M2), combined with a linear interpolation of extreme event fluxes. Sampling can be reduced to every fourth day, with both method-agreements and accuracies <±10%, using 7year averages. The specific annual method-agreements were <±10% for all years and the specific annual accuracies <±20% for 6years out of 7. The rating curves were less sensitive to day-to-day variations in the measured suspended sediment concentrations. The discharge weighted mean was not recommended in the high-Arctic Zackenberg River, unless sampling was done bi-daily, every day and events sampled high-frequently.