An overview of the layered structure of the polar ice sheet based on crystalline textural properties of the Dome Fuji summit ice core, Antarctica

This study provides an overview of the layered structure of Antarctic ice sheets, focusing on the crystalline textural properties and deformational regimes in the Dome Fuji ice core. Polar ice sheets consist of layers with diverse rheological characteristics, shaped by depositional processes such as atmospheric aerosol deposition. Layer thickness varies from millimeters (annual layers) to thicknesses spanning glacial-interglacial periods, with the initial ice fabric forming during firnification.

Key factors influencing the rheology of ice include ion content (e.g., Cl−, F−, NH4+) and insoluble particles such as salts and dust. Ions can substitute within the ice crystal lattice, affecting dislocation density, viscosity, and deformation behavior. These influences persist from firnification to the basal layers of the ice sheet. Notably, salt inclusions have larger volume fractions than dust particles, significantly impacting microstructure evolution.

The ice sheet’s deformation can be divided into two regimes: the upper 80% of the ice sheet, characterized by lower strain and temperature gradients, and the lower 20%, where higher temperatures and strain induce complex recrystallization processes. Four primary factors drive the evolution of crystal orientation fabrics and microstructures: (i) temperature conditions, (ii) strain configurations, (iii) insoluble particle effects, and (iv) dynamic recrystallization, including grain boundary migration and the formation of new grains. These processes result in a deformational history unique to each layer, spanning up to one million years.

Understanding these layered structures has significant implications. For ice sheet modeling, they provide constraints on strain values and inform models of vertical thinning. For ice core sciences, the layered structure highlights the importance of drilling sites. Dome summit sites preserve continuous, undisturbed records of ancient ice, while locations away from domes risk basal disturbances, including folding, faulting, and layer mixing.

This research enhances our understanding of ice sheet dynamics and supports the development of improved dating models, contributing to studies of Earth's climate history over millennia.