Fractures in glaciers - Crack tips and their stress fields by observation and modeling

Abstract

High-resolution optical camera systems are opening new opportunities to studyfractures in ice. Here, we present data obtained from the Modular Aerial CameraSystem camera system operated onboard of Alfred Wegener Institute HelmholtzCentre for Polar and Marine Research (AWI) polar aircraft in northeast Green-land in 2022. In addition, we are using optical and radar satellite imagery. Thestudy area is the 79N Glacier (Nioghalvfjerdsbræ, 79NG), an outlet glacier of theNortheast Greenland Ice Stream. We found that crack tips are exhibiting addi-tional isolated cracks ahead of the main crack. Subsequent crack propagationis starting from those isolated cracks, leading to an advance of the crack, withbridges between crack faces. The bridges provide information of the episodiccrack propagation. Fractures have typically a length scale of kilometers andthe distance of crack faces is in the order of meters to tenths of meters. Frac-ture modes will be inferred from stress fields computed by an inverse modelingapproach using the Ice Sheet and Sea Level System Model. To this end, a surfacevelocity field derived from satellite remote sensing is used for the optimal controlmethod that constrains model parameters, for example, basal friction coefficientor rheology.