The Effects of Soluble Impurities on the Flow and Fabric of Polycrystalline Ice

Abstract:

It is well known that the Earth’s large continental ice sheets contain a wide variety of naturally occurring physical impurities, both soluble and insoluble. Understanding how these impurities may affect the rheology, intrinsic thermodynamic properties, and ultimate fate of these ice sheets, however, is much less understood. One such soluble impurity thought to be of critical importance and already shown to be catalytic in the flow of single crystal ice, is sulfuric acid. In order to further investigate the potential effects that sulfuric acid may also have on the flow and ductility of polycrystalline ice, we have established a procedure for preparing polycrystalline ice specimens that have been doped with known amounts of sulfuric acid which can then be used for conducting creep tests in uniaxial tension while subjected to a low (less than 1 MPa) but constant applied stress. These creep tests are conducted at -10 and -20 degrees C and each specimen is taken to 10% strain. The influence of a variable temperature is thought to be of particular significance as other previous works have already shown that the effects of soluble impurities can be directly observed in the deformation of the ice crystal lattice and grain boundaries. Following the completion of each creep test, post-creep microstructural analysis is conducted via polarized light microscopy, optical environmental SEM imaging, and Raman spectroscopy.