Characterizing the Supraglacial Hydrological Environment of Western Greenland: Investigating Lake and Channel Distribution, and Melt Channel Discharge Capacity

• Main Author: VanderBerg, Justin
• Other Authors: Derrick Lampkin
• Format: Text
• Language: English
• Published: Penn State 2010
• Subjects: Geography; Greenland; Jakobshavn
• Online Access: http://etda.libraries.psu.edu/theses/approved/WorldWideIndex/ETD-5977/index.html

The supraglacial hydrologic network is composed of lakes and interconnecting channels that transport water to, between, and from lakes. The spatial distribution of supraglacial lakes has been hypothesized to be dominantly controlled by the component of surface roughness influenced by basal topography. Basal topography and surface roughness profiles within the Jakobshavn Isbrae drainage basin in western Greenland, acquired from an ice penetrating radar echo sounder, were analyzed through Fourier and wavelet decompositions. Spectral analyses of basal-to-surface roughness transfer under a range of ice thickness were compared with the spatial distribution of lakes mapped from high resolution Landsat imagery. Fourier analysis identifies dominant signals in both the basal and surface profiles to be ranging between wavelengths of 1.25-12.5km. The strongest peaks of transfer of basal signals to the surface were identified at wavelengths ~11km and ~5km. Wavelet analysis identifies these peaks with thicker (1200 1400m) and thinner (500 700m) ice respectively, and also identifies surface frequencies not present in the basal signal indicating some influence from other forcings. Spatial autocorrelation analysis of supraglacial lake distribution identifies periodicities at spacings of 1.9km, 5.6km, 11km, 24km, and 30km, of which those at 5.6km and 11km correspond with the dominant frequencies present in the basal and surface profiles over thinner and thicker ice respectively. These ~5km and ~11km frequency components present in the basal topography, surface roughness, and lake distribution are within the theoretical transfer window of basal to surface transfer as a function of ice thickness. Thus, basal topography influences surface roughness and lake distribution, but does not explain all the variation present in lake distribution. The spatio-temporal distribution of supraglacial melt channels and their relationship to supraglacial lakes over the Jakobshavn Isbrae region of Western Greenland was analyzed using Landsat ETM+ panchromatic images during the 2007 melt season. A total of 1189 melt channels were delineated and show an increase in the number of melt channels throughout the season, reaching a peak on August 9. Melt channels are observed at elevations up to 1647m on August 9, and attain a minimum average slope of 0.009 on July 8. The hydrologic channel network demonstrates a progression towards terminal flow into moulins and crevasses through the melt season. Coupling this baseline survey with a thermal stream-erosion model produces the first regional scale estimates of melt channel discharge capacity. Initial results show that the melt channel network is capable of transporting up to 11000m3/day of water. Understanding the various processes that determine the distribution and redistribution of surface melt water will improve our understanding of the supraglacial hydrologic environment.