Seasonal evolution of supraglacial stream network in southwest Greenland
Abstract
Meltwater on the Greenland ice sheet surface is routed through supraglacial streams and river networks before descending into moulins and crevasses. These networks impact the timing and amplitude of moulin discharge which in turn may influence basal sliding and ice motion. However, despite its importance, surface routing through these stream networks is poorly understood. In this study, we collected 45 discharge measurements and continuous water level stage measurements from 13 June - 13 August 2016, which provide an unprecedented record of stream flow within a ~0.53 km2 supraglacial catchment near the ice sheet margin in southwest Greenland. We calculate a robust rating curve (R2 = 0.928) relating stage to discharge, revealing discharge variations from 0.0-1.0 m3/s with a peak in mid-July. Changes in the efficiency of meltwater transport of the supraglacial stream network were investigated using amplitude and time to peak of the daily stream hydrograph. Model studies show that large amplitudes and early peak times characterize a well-developed stream network when meltwater is evacuated quickly from its origin to the outlet. In our study, we found that the amplitude of daily discharge increased from 0.2 m3/s in mid-June to 0.8 m3/s in mid-July, followed by a continuous high plateau until month's end and a gradual decrease starting early August. Time to daily peak discharge decreases by 2 hours from mid-June through the end of July. These results suggest that the stream network efficiency has marked seasonal variation and peaks in mid to late July near the ice sheet margin in southwest Greenland. Understanding seasonal changes in the efficiency of supraglacial stream network is vital for determining the impact of surface mass balance on ice dynamics and should be incorporated into ice sheet models to accurately predict the short-term timing of Greenland's contributions to sea-level rise.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.C11A..04M
- Keywords:
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- 0720 Glaciers;
- CRYOSPHERE;
- 0726 Ice sheets;
- CRYOSPHERE;
- 0730 Ice streams;
- CRYOSPHERE;
- 0776 Glaciology;
- CRYOSPHERE