Similarity of organized patterns in driving and basal stresses of Antarctic and Greenland ice sheets beneath extensive areas of basal sliding

The rate of ice transport from the interior of ice sheets to their margins, and hence the rate with which it contributes to sea level, is determined by the balance of driving stress, basal resistance and ice internal deformation. Using recent high resolution observations of the Antarctic and Greenland ice sheets, we compute driving stress and ice deformation velocities, inferring basal traction by inverse techniques. The results reveal broad scale organization in 5–20 km band-like patterns inboth the driving and basal shear stresses located in zones with substantial basal sliding. Both ice sheets experience basal sliding over areas substantially larger than previously recognized. The likely cause of the spatial patterns is the development of a band-like structure in the basal shear stress distribution that is the results of pattern-forming instabilities related to subglacial water. The similarity of patterns on the Greenland and Antarctic Ice Sheets suggests the flow of ice sheets is controlled by the same fundamental processes operating at their base, which control ice-sheet sliding and are highly variable on relatively short spatial and temporal scales, with poor predictability. This has far-reaching implications for understanding of the current and projection of the future ice sheets’ evolution