Supraglacial Stream Morphology and Flow Characteristics from Ultra-High Resolution Bathymetric Mapping
Abstract
Surface melting increasingly dominates the mass balance of the Greenland Ice Sheet. Surface meltwater flows into complex supraglacial stream networks that are significantly darker than the surrounding ice. These streams usually carry sediment along their beds which exacerbate decreases in albedo. The rapidly evolving morphology of supraglacial streams in response to changing meltwater inputs may also add to this process by redistributing sediment and potentially changing their ability to efficiently route meltwater off the surface of the icesheet. Despite their disproportionately large impact on ablation zone albedo, little is known about the flow characteristics of supraglacial streams, how these characteristics may interact with stream sediment, and how they will be impacted by climate change. Here we measure a single supraglacial stream in southwest Greenland using high resolution GPS mapping, velocity measurements, and UAV imagery. Analysis of these inputs produced a centimeter scale bathymetric map, a week-long stream discharge time series, and map of initial sediment distribution. Together, they give clues as to how the geometry and meltwater input into supraglacial stream systems impact the aerial coverage of water and sediment. Large diurnal and spatial variability in water depth and surface slope cause large fluctuations in sediment transport capacity. The bed of supraglacial streams changes roughness significantly in response to flow velocity so that small increases in meltwater supply result in large changes in bed properties. This correlation between bed roughness and water velocity may help us better understand how supraglacial streams my influence the albedo of the ablation zone in response to a warming climate.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.C51G1154L
- Keywords:
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- 0720 Glaciers;
- CRYOSPHEREDE: 0726 Ice sheets;
- CRYOSPHEREDE: 1827 Glaciology;
- HYDROLOGYDE: 1863 Snow and ice;
- HYDROLOGY