Towards a Decadally-Resolved Radiocarbon Calibration for the Last Glacial Period (30,000-11,700 years ago) Using New Zealand Kauri (Agathis australis)

过去的气候变化为比较现在和未来的变暖提供了一个关键的基线。然而，不幸的是，尽管已经进行了许多跨越最后一个冰河时代的重建，但大多数记录都不能精确地相互关联。主要问题是绝大多数记录都是放射性碳年代测定的，没有国际公认的校准曲线，排除了在日历时间尺度上进行重建的可能性，并阻止了与高分辨率和绝对年代序列（如冰芯）进行可靠的比较。这是科学界面临的一个重大问题。对放射性碳定年记录的“校准”可能导致气候变化在世界各地领先、滞后或同步的结论，这取决于使用哪种转换，从而阻止科学界详细了解地球系统的变化机制。准确和精确的放射性碳校准曲线应该基于绝对定年记录，该记录具有在形成时直接从大气中掺入的碳。树木年轮已被证明是一个很好的资源，用于这一目的。目前，国际上公认的基于北美和欧洲树木年轮测年材料的绝对测年校准曲线只能追溯到12 410年;由于过去冰盖对材料的破坏，在北方半球大幅延长记录的前景并不乐观。在横跨新西兰北方的泥炭沼泽中埋藏着古老的针叶树贝壳杉。据我们所知，世界上没有其他地方拥有如此丰富的亚化石木材资源，能够捕获全部放射性碳。在这些沼泽中保存的时间跨度确实是巨大的;跨越超过130，000年。这些树木的比例很大，几乎保存完好;每棵树的直径可达4米，寿命长达2000年。在这个珍贵的档案中，是大气放射性碳水平和过去气候变化的年度记录。这是一个独特的资源。然而，不幸的是，木材也是家庭家具，艺术和手工艺品的高价。结果是，埋藏的木材正以惊人的速度被开采，并将在十年内耗尽。在这个项目中，我们将在贝壳杉永远消失之前收集和分析它。我们将重点对树木年轮进行全面测年，以确定大气中放射性碳的变化水平，使用在30，000至11，700年前收集的古代日志。这项研究的结果将有助于精确校准过去气候，环境和考古变化的放射性碳年代序列，从而帮助我们提高对地球系统的理解。

Past climate change provides a critical baseline against which to compare present and future warming. Unfortunately, however, although numerous reconstructions spanning the last ice age have been made, most of the records cannot be precisely correlated to one another. The main problem is the vast majority of records have been radiocarbon dated for which no internationally-accepted calibration curve exists, precluding the placement of reconstructions on a calendar timescale and preventing robust comparisons with high-resolution and absolutely dated sequences (such as ice cores). This is a significant problem for the scientific community. 'Calibration' of radiocarbon-dated records can result in the conclusion that climate change led, lagged or was synchronous around the world depending on which conversion is used, preventing the scientific community from gaining a detailed understanding of mechanisms of change in the Earth system. An accurate and precise radiocarbon calibration curve should be based on an absolutely dated record that has carbon incorporated directly from the atmosphere at the time of formation. Tree rings have proven to be an excellent resource for this purpose. At the moment, the internationally-accepted absolutely-dated calibration curve based on North American and European tree-ring dated material only extends back to 12,410 years; the prospect of significantly extending the records in the northern hemisphere is not high due to destruction of material by past ice sheets. Buried in peat bogs across northern New Zealand are ancient conifer trees called kauri. We know of nowhere else in the world with such a rich resource of subfossil wood that is capable of capturing the complete range of radiocarbon. The time span preserved within these bogs is truly enormous; spanning more than 130,000 years. These trees are of vast proportions and almost perfectly preserved; individual trees can measure up to 4 metres across and live for up to 2000 years. Within this precious archive is an annual record of changing atmospheric radiocarbon levels and past climate. This is a unique resource. Unfortunately, however, the timber is also highly-prized for household furniture, arts and crafts. The result is the buried wood is being mined at an alarming rate and will be exhausted within ten years. In this project, we will collect and analyze the kauri before it is lost forever. We will focus on undertaking comprehensive dating of the tree rings to determine changing levels of radiocarbon in the atmosphere using ancient logs that have been collected within the period spanning 30,000 to 11,700 years ago. The results from this study will help to precisely calibrate radiocarbon-dated sequences of past climate, environmental and archaeological change, thereby helping us to improve our understanding the Earth system.