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研究的重要工具。因此，校准海洋放射性碳年龄至关重要。然而，目前可用的海洋校准曲线MarCal13被认为是一个假设的校准曲线，仅依赖于对不同沉积物，热带珊瑚和部分有孔虫的少量测量。该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，我们证明了冰川珊瑚与大气演化的偏差很小。这种中深度（500 - 900m）海洋放射性碳衰减的成因与亚热带大西洋内普遍通风良好的水团相互作用和碳的向下混合有关。从冷水珊瑚省收集的大量沉积物岩心提供了年龄在14至60岁之间的化石珊瑚碎片，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U-Th定年法，亚热带大西洋放射性碳平衡的变化可以达到前所未有的年龄精度和绝对定时。因此，该项目旨在提高我们对海洋放射性碳随时间变化的理解，如果成功，该项目将提供显着改进的MarCal13记录，这将作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.