Relation between neighbouring grains in the upper part of the NorthGRIP ice core — Implications for rotation recrystallization

We propose a new method to investigate the relationships between neighbouring crystals and apply it to the textures measured along the upper 900 m of the NorthGRIP ice core. This method shows unexpected correlations between neighbours in the so-called normal grain growth regime, questioning the classical view on the onset of rotation recrystallization in ice-sheets. Moreover, the fractionation rate associated to the rotation recrystallization appears constant through time. Finally, grains with low-angle boundaries do not present a special distribution pattern of their c-axes. This suggests that rotation recrystallization is an isotropic process not affected by the direction of the macroscopic strain.