Collaborative Research: Trapped Gas Composition and the Chronology of the Vostok Ice Core

高纬度深冰芯包含极地温度、大气尘埃负荷(和大陆干旱)、温室气体浓度、生物圈状况和过去环境的其他基本性质的基本记录。如果要充分认识到这些记录的重要性，就需要对它们进行准确的年代学研究。测年挑战刺激了轨道调整的努力。在这种方法中，人们在允许的范围内改变时间刻度，以优化古环境属性与随时间变化的日照曲线之间的匹配。由于直接的日照强迫，理想的性质会随时间变化。它不会受到复杂的气候反馈和遥相关的影响，而且它将提供高信噪比的干净记录。冰核捕获气体的O_2/N_2比是这种性质的有力论据，而且有证据表明，这种大气比几乎不变的性质与当地夏季的日照有关。该奖项将支持一个项目，在Vostok冰芯中以1 KYR的间隔分析~115-400 ka的O2/N2比率。将进行Ar/N_2、Ne/N_2和重惰性气体比值的辅助测量，以了解气泡关闭分馏及其在Vostok圈闭气体记录中的表现。O2/N2的变化将与沃斯托克的夏季日照相匹配，以实现对沃斯托克核心的高精度年代学。然后将重新检查沃斯托克和其他相关的气候记录，以提高我们对更新世气候变化动力学的理解。

High latitude deep ice cores contain fundamental records of polar temperatures, atmospheric dust loads (and continental aridity), greenhouse gas concentrations, the status of the biosphere, and other essential properties of past environments. An accurate chronology for these records is needed if their significance is to be fully realized. The dating challenge has stimulated efforts at orbital tuning. In this approach, one varies a timescale, within allowable limits, to optimize the match between a paleoenvironmental property and a curve of insolation through time. The ideal property would vary with time due to direct insolation forcing. It would be unaffected by complex climate feedbacks and teleconnections, and it would give a clean record with high signal/noise ratio. It is argued strongly that the O2/N2 ratio of ice core trapped gases is such a property, and evidence is presented that this property, whose atmospheric ratio is nearly constant, is tied to local summertime insolation. This award will support a project to analyze the O2/N2 ratios at 1 kyr intervals from ~ 115-400 ka in the Vostok ice core. Ancillary measurements will be made of Ar/N2, and Ne/N2 and heavy noble gas ratios, in order to understand bubble close-off fractionation and its manifestation in the Vostok trapped gas record. O2/N2 variations will be matched with summertime insolation at Vostok to achieve a high-accuracy chronology for the Vostok core. The Vostok and other correlatable climate records will then be reexamined to improve our understanding of the dynamics of Pleistocene climate change.