Characterizing the internal structure of laboratory ice samples with nuclear magnetic resonance

Due to solute impurities and freezing-point depression in polycrystalline ice, a complicated and dynamic network of liquid water forms within the solid ice matrix at the boundaries between ice crystal grains. Impurity concentrations, temperature and pressure influence this network structure and impact physical, transport and rheological properties of ice. However, the nature of this internal network structure is not fully understood. Here we utilize nuclear magnetic resonance (NMR) measurements of diffusion and magnetic relaxation to study the geometry and interconnectivity of the liquid-filled network in laboratory ice, formed from a 7 g L NaCl solution, and its evolution due to recrystallization processes. Additionally, we apply these NMR measurements to observe the impact on ice microstructure of an ice-binding protein (IBP) excreted by the V3519-10 organism (Flavobacteriaceae family) isolated from the Vostok ice core in Antarctica. Recrystallization inhibition was observed as a function of IBP concentration. This work demonstrates the utility of advanced NMR techniques for applications to ice microstructure and has broader implications for understanding geophysical properties of cryospheric systems.