Temperature Dependence of Ice Crystal Size in Tibetan Ice Cores

Abstract. The ice crystal size in ice core can not only reflect the glacial strain process but also be connected to climate change. However, the process of ice crystal size variation along ice core in mountain glacier remains largely unexplored. Here, we continuously measured the ice grain areas along two deep ice cores drilled from the Tibetan Plateau, and found that the two ice cores exhibit vertical grain area differentiation at the hundred-meter scale, analogous to polar ice-core profiles, relatively higher temperatures significantly accelerate grain growth and result in larger grain areas. Refreezing under warm conditions gives rise to abrupt increases in grain area within melt-refrozen layers, whereas impurities result in abrupt decreases in grain area within cloudy bands. Together, these two factors drive centimeter-scale fluctuations in grain area. Even so, we also found that grain area exhibits a significant correlation with δ¹⁸O in ice layers where Rotation Recrystallization (RRX)-induced refinement is negligible, indicating that the ice crystal size of mountain glaciers ice core can retain temperature signals.