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

Abstract

AbstractThe 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 analysed through fourier and wavelet decompositions. Spectral analyses of basal‐to‐surface transfer under a range of ice thickness were compared with 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 1·25–12·5 km. The strongest peaks of transfer of basal signals to the surface were identified at wavelengths ∼11∼5 km. Wavelet analysis identifies these peaks with thicker (1200–1400 m) and thinner (500–700 m) ice respectively and also identifies surface frequencies not present in the basal signal indicating some influence from other factors. Spatial autocorrelation analysis of supraglacial lake distribution indentifies high correlations at 1·9, 5·6, 11, 24, and 30 km lags. Lags at 5·6 and 11 km correspond to dominant frequencies present in the basal and surface profiles over thinner and thicker ice respectively. These ∼5 and ∼11 km 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. The transect analysed in this study does not contain wavelengths in the surface structure that are less than the ice thickness, even though there are relatively higher frequencies present in the surface profile between 0 and 15 km that have less power in the basal profile. Copyright © 2011 John Wiley & Sons, Ltd.