Atlantic Radiocarbon Calibration using framework forming cold water corals

放射性碳定标是古气候学和古海洋学的重要工具。因此，海洋放射性碳定年的校准至关重要。然而，目前可用的海洋校准曲线MarCal13被认为是一条假设的校准曲线，它只依赖于对各种沉积物、热带珊瑚和部分有孔虫的少量测量。这条校准曲线需要显著改进。冷水珊瑚(或深海珊瑚)的U-Th和14C耦合测年主要用于追踪和量化深水循环和碳循环的变化。通过我们对摩洛哥珊瑚礁化石珊瑚的初步研究，我们证明冰川珊瑚只显示出与大气演化的微小偏差。这种中等深度(500-900米)海洋放射性碳变率减弱的原因与一般通风良好的水团的相互作用和副热带大西洋内向下混合的碳有关。从冷水珊瑚省收集了许多沉积物岩心，提供了跨度为14至60年的珊瑚化石碎片，从而跨越了整个放射性碳校准期。因此，我们处理了一个独特的档案来追踪近地表海洋中的放射性碳变化。通过质谱仪U-Th定年，可以获得亚热带亚特兰蒂斯放射性碳平衡的变化，其年龄精度和绝对时间都是前所未有的。因此，该项目旨在促进我们对海洋放射性碳随时间变化的了解，如果成功，该项目将显著改进MarCal13记录，这将成为海洋沉积物和碳循环年代学研究的基准。

Radiocarbon calibration is a major tool for paleoclimatology and paleoceanography. Calibrating marine radiocarbon ages is thus of crucial importance. However, the presently available marine calibration curve MarCal13 is thought to be a hypothetical calibration curve relying on only few measurements from varved sediments, tropical corals and partly foraminifera. This calibration curve requires significant improvement. Coupled U-Th and 14C dating of cold-water corals (or deep sea corals) is mostly used to trace and quantify changes in deep water circulation and carbon cycling. Through our preliminary work on fossil corals from the Moroccan coral reefs we demonstrate that glacial corals reveal solely minor deviation from the atmospheric evolution. The origin of such damped oceanic radiocarbon variability at mid-depth (500 - 900m) is related to the interaction of generally well-ventilated water masses and the downward mixing of carbon within the subtropical Atlantic. Numerous sediment cores from the cold-water coral province have been collected providing fossil coral fragments which span 14 to 60 kyrs in age, thus spanning the entire radiocarbon calibration period. Consequently, we dispose a unique archive to trace radiocarbon variations in the near surface ocean back in time. Through mass spectrometric U-Th dating changes of the subtropical Atlantics radiocarbon balance can be achieved at yet unprecedented age precision and absolute timing. Hence, this project aims to advance our understanding of the marine radiocarbon variability through time and if successful this project will deliver a significantly improved MarCal13 record, which will serve as a benchmark for chronological studies of marine sediments and carbon cycling.