Fractal Properties of Greenland Isolines

Abstract

The shape of Earth’s surface topography is determined by numerous competing processes that act to either roughen or smoothen the surface. Hence, calculating topographic roughness is a useful technique for understanding the relative importance of these processes. This study analyzes the relative surface roughness of the Greenland Ice Sheet by calculating the fractal dimension of surface elevation isolines. It is shown that the fractal dimension of isolines decreases at higher elevations for nearly all the ice sheet catchments. However, the magnitude of fractality, which represents the relative complexity or roughness of the surface, is spatially variable. Catchments in the central-east of the ice sheet have the highest fractal dimension, and the north catchment has the lowest fractal dimension. Multi-fractality at lower elevations for several catchments is observed including the southeast catchment, indicating that these catchments have variable dominant forcings at different length scales. Exploring the local variation of fractal dimensions shows that the majority of isolines with high fractal dimension are clustered in the central-east region and persist in contours up to 2500 m elevation. However, it is shown that local fractal dimensions are related to surface elevation, bed elevation, and ice thickness. It is also shown that local fractal dimensions are correlated with the ruggedness of basal topography (defined as the difference between the highest and lowest elevation in a window of $$3\times 3$$ pixels on a 150 m grid). This analysis serves as a qualitative approach for investigating the processes that control the geometry of ice caps on other terrestrial planets.