A new method of resolving annual precipitation for the past millennia from Tibetan ice cores

Abstract. Net accumulation records derived from ice cores provide the most direct measurement of past precipitation. However, quantitative reconstruction of accumulation for past millennia remains challenging due to the difficulty in identifying annual layers in the deeper sections of ice cores. In this study, we propose a new method to quantify annual accumulation from ice cores for past millennia, using as an example an ice core drilled at the Chongce ice cap in the northwestern Tibetan Plateau (TP). First, we used the Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) technology to develop an ultra-high-resolution trace element records in three sections of the ice core and identified annual layers in each section based on seasonality of these elements. Second, based on nine 14C ages determined for this ice core, we developed a two-parameter flow model to established the thinning parameter of this ice core. Finally, we converted the thickness of annual layers in the three sample sections to past accumulation rates based on the thinning parameter derived from the ice-flow model. Our results show that the mean annual accumulation rate for the three sample sections are 102 mm/year (2511–2541 a B.P.), 76 mm/year (1682–1697 a B.P.) and 84 mm/year (781–789 a B.P.). For comparison, the Holocene mean precipitation is 103 mm/year. This method has the potential to reconstruct continuous high-resolution precipitation records covering millennia or even longer time periods.