A preliminary investigation of the influence of basal and surface topography on supraglacial lake distribution near Jakobshavn Isbrae, western Greenland

摘要

The spatial distribution of supraglacial lakes has been hypothesized to be dominantly controlled by the component of surfacenroughness influenced by basal topography. Basal topography and surface roughness profiles within the Jakobshavn Isbraendrainage basin in western Greenland, acquired from an ice-penetrating radar echo sounder, were analysed through fourier andnwavelet decompositions. Spectral analyses of basal-to-surface transfer under a range of ice thickness were compared withnspatial distribution of lakes mapped from high-resolution Landsat imagery. Fourier analysis identifies dominant signals innboth the basal and surface profiles to be ranging between wavelengths of 1D25–12D5 km. The strongest peaks of transfer ofnbasal signals to the surface were identified at wavelengths .11 .5 km. Wavelet analysis identifies these peaks with thickern(1200–1400 m) and thinner (500–700 m) ice respectively and also identifies surface frequencies not present in the basal signalnindicating some influence from other factors. Spatial autocorrelation analysis of supraglacial lake distribution indentifies highncorrelations at 1D9, 5D6, 11, 24, and 30 km lags. Lags at 5D6 and 11 km correspond to dominant frequencies present in thenbasal and surface profiles over thinner and thicker ice respectively. These .5 and .11 km frequency components present innthe basal topography, surface roughness, and lake distribution are within the theoretical transfer window of basal-to-surfacentransfer as a function of ice thickness. The transect analysed in this study does not contain wavelengths in the surface structurenthat are less than the ice thickness, even though there are relatively higher frequencies present in the surface profile betweenn0 and 15 km that have less power in the basal profile. Copyright  2011 John Wiley & Sons, Ltd.