1University of Colorado, Department of Geological Sciences, Boulder, CO, USA
2University of Colorado, Community Surface Dynamics Modeling System, INSTAAR, Boulder, CO, USA
3University of Colorado, CIRES, Boulder, CO, USA
4USGS Alaska Science Center, Anchorage, AK, USA
5University of Copenhagen, Copenhagen, Denmark
Abstract. We test the hypothesis that increased meltwater runoff from the Greenland Ice Sheet (GrIS) has elevated the suspended sediment concentration (SSC) of six river plumes in three fjords in southwest Greenland. A~SSC retrieval algorithm was developed using the largest in situ SSC dataset for Greenland known and applied to all cloud free NASA Moderate Resolution Imaging Spectrometer (MODIS) reflectance values in the Terra image archive (2000 to 2012).
Melt-season mean plume SSC has not increased as anticipated, with the exception of one river. However, positive statistically significant trends involving metrics that described the duration and the spatial extent of river plumes were observed in many locations. Zones of sediment concentration > 50 mg L−1 expanded in three river plumes, with potential consequences for biological productivity. The high SSC cores of river plumes (> 250 mg L−1) expanded in one-third of study locations. When data from study rivers was aggregated, higher volumes of runoff were associated with higher melt-season mean plume SSC values, but this relationship did not hold for individual rivers. High spatial variability between proximal plumes highlights the complex processes operating in Greenland's glacio-fluvial-fjord systems.