Cryospheric and Polar Processes Seminar

Beyond water: impact of Greenland’s melt on its coastal sediment dynamics

Irina Overeem, INSTAAR, University of Colorado

Abstract:

Melt of the Greenland Ice Sheet releases large amounts of freshwater into the ocean, raising sea level globally. What else drains out of Greenland with this freshwater?
Here, we use field measurements, massively parallel satellite data analysis, and modeling to investigate sediment and nutrient fluxes and its possible impacts on biogeochemical cycles and the coastal zone. 
In-situ data and satellite methods demonstrate a tremendous amount of sediment drain from Greenland. River suspended sediment concentrations are highly variable, which is explained by a first-order model of glacial dynamics, with meltwater drainage basins with high glacier velocities producing the highest sediment concentrations. We find that, although runoff from Greenland represents only 1.1% of the Earth’s freshwater flux, the Greenland ice sheet produces approximately 8% of the modern fluvial export of fine sediment to the global ocean.
Whereas we do not have in-situ data on coarse bedload sediments, we infer coarse sediment transport from river delta dynamics. Systematic mapping of 121 Greenland’s deltas used historical air photos and more recent satellite imagery. We found that southwestern Greenland deltas were largely stable from the 1940s to 1980s, but prograded in a warming Arctic from the 1980s to 2010s. Statistical analysis corroborates that delta progradation has dominantly been driven by higher meltwater runoff from the Greenland Ice Sheet.
Greenland’s sediment dynamics may be unique in the world. As most of world’s rivers are carrying less sediment due to damming and temperate deltas are drowning from human-caused subsidence and global sea level rise, Greenland’s sediment fluxes are, in contrast, advancing because of the increased mass loss from Greenland’s land-based ice.