青藏高原冰芯定年方法回顾及新技术展望

冰芯高分辨率高保真地记录了过去不同时间尺度气候环境变化历史，而冰芯精确定年是重建过去气候环境演化的先决条件。通过回顾青藏高原冰芯定年的常用方法，提出了目前冰芯定年仍存在的挑战和机遇。通常的冰芯定年方法包括基于冰芯季节变化信号的数年层方法、放射性标志层定年、冰川流动模型、基于其他已知时间序列的对比定年，以及放射性同位素定年。最可靠的方法是数年层的方法，但受到冰川中下部年层逐渐减薄的制约，冰川流动模型主要应用于冰芯中下部定年，但存在不确定性较大而且难以验证的难题。未来冰芯学科发展对冰芯定年提出了更高要求，随着测量技术与手段的突破，新的方法与技术开始在极地冰芯与高山冰芯定年研究中展示了广泛的应用前景。冰芯连续测量技术（如冰芯同位素连续测量技术、激光剥蚀等离子体质谱技术）大幅度提高了冰芯测量结果的时间精度，有可能把数年层的定年方法延推到冰芯底部；基于“原子阱痕量分析”（Atom Trap Trace Analysis，ATTA）的惰性气体（⁸⁵Kr、⁸¹Kr、³⁹Ar）放射性测年技术是一项革命性的技术，由于惰性气体在大气中的稳定性与均匀性使其在不同时间尺度冰川冰的绝对定年中发挥出优势。低浓度的可溶性有机碳的¹⁴C定年也从实验室探索阶段开始转入试用阶段，而且用冰量低，有望解决冰芯中碳含量低，定年困难的窘迫状况。此外，人类活动影响之前处于自然背景下的冰芯³H低本底测量技术结合数据处理方法，有望恢复过去100~200年与太阳活动周期相关的信号，将补充放射性标志层只有近代结果的不足。这些新的技术与方法在冰芯定年中的应用有望进一步推动中低纬度高山冰芯研究。

A review and perspective of the ice core dating methods on the Tibetan Plateau

Ice core is nature archives to rebuild paleo climate and environment in varying time scale with high resolution and high fidelity， while precise ice core dating is the prerequisite for such a purpose. This paper presented a review of ice core dating methods mostly used in the Tibetan Plateau ice core research， and also addressed the challenge and opportunity involved in the ice core dating. Conventional dating methods includes annual layer counting， radioactive laying marker， glacier flow modeling， comparison with other established chronology， and radioactive dating. The most reliable dating method is the annual layer counting. However， this method is limited in the middle and lower part of ice core as the annual layer become too thin to be identified as ice moves towards the bottom of glacier. The glacier flow modeling is restricted by larger uncertainty in the dating result and hard to be verified. The achievements in the ice core research require an improvement in the ice core dating precision. Therefore， we also reviewed the new technology and methods emerged in recent years made available in the ice core dating. Ice core continuous measuring technique （e g.， ice core water isotope continuously measurement， laser ablation-inductively coupled plasma-mass spectrometry （LA-ICP-MS））， provides sub-millimeter-scale sampling resolution， and therefore， can extend the annual layer counting method to the bottom of ice core. Noble gas （⁸⁵Kr、⁸¹Kr、³⁹Ar） radioactive dating method based on ATTA （Atom Trap Trace Analysis） provided a revolutional method for absolute dating of glacier ice， as for their stability and homogeneity in the atmosphere. Dissolved organic carbon （DOC） ¹⁴C dating will make its practice in laboratory ice dating due to its less ice sample size used and showed its potential in the ice core dating. In addition， low level ³H in ice core measurement， particular prior to the nuclear test epoch， can be used to dating the ice core age in the past 1~2 centuries as for its concentration steps with the solar cycle. These new methods and technique provide the potential wide practice in the recent and future alpine ice core dating， and therefore， benefit the future ice core research.