The Impacts of the Microstructural Location of H2SO4 on the Flow of Polycrystalline Ice

The effects of soluble impurities on the flow of glaciers and ice sheets as well as the effects of ice flow on impurities migration are not well understood. This study investigates the effects of sulfuric acid (H2SO4) concentrations ranging from 10 to 25 ppm on the flow and fabric of polycrystalline ice under compression at temperatures of -3°C and -12°C. The results show that H2SO4-doped polycrystalline ice deforms significantly faster than high-purity polycrystalline ice, with the deformation rate being 1.5 to 3 times higher. At -12°C, the presence of H2SO4 within the grains induces the most ice softening, whereas at -3°C, H2SO4's softening effects are observed both within the grains and at grain boundaries. The migration of H2SO4 to grain boundaries during deformation leads to the formation of a liquid-like layer, with increased solubility at higher temperatures potentially homogenizing the impurities within the ice matrix. This homogenization at -3°C suggests that post-depositional processes near the bed of ice sheets could significantly alter sulfate records. At -12°C, where homogenization is absent, impurity-induced dislocation processes may heavily influence deformation and impurity migration. Additionally, the comparison of natural ice with lab-grown samples indicates that fabric development significantly impacts compressive strength and creep rates, with implications for the understanding of impurity-induced deformation processes in polar ice.