Collaborative Research: The Ocean-Atmosphere Carbon Cycle and Climate Change: Constraints from Radiocarbon and Climate History

pi将获得并解释来自美国密苏里州裂隙洞和中国南京Hulu洞相同样品的14C/12C记录和高分辨率气候记录。这些记录将使用高精度230Th和231Pa技术进行独立和精确的测年，从而确定初始14C/12C值并建立绝对年表。pi将使用这些记录(1)重建整个放射性碳时间尺度（最近45天）的大气14C/12C，(2)将这些记录直接与来自相同样品的气候记录进行比较。前者将限制冰川时期以来海洋-大气碳循环的运作。后者将描述碳循环变化与气候变化之间相互作用的特征。两者都对理解当前和未来的碳循环有影响。最近的研究表明，在44至34 Ka之间的大部分时间里，大气中的14C/12C非常高，而且变化很大。放射性碳值通常远高于现代碳循环所能达到的值，即使地球磁场和太阳磁场可以忽略不计。因此，这些数据需要现代碳循环和冰川碳循环之间的显著差异，以及冰川碳循环的大时间变化。这项工作的深远影响需要在巴哈马以外的地点进行复制，巴哈马是收集这些证据的地点。

The PIs will obtain and interpret cave speleothem 14C/12C records and high-resolution climate records from the same samples from Crevice Cave, Missouri and Hulu Cave, Nanjing, China. The records will be dated independently and precisely with high precision 230Th and 231Pa techniques enabling determination of initial 14C/12C values and establishment of an absolute chronology. The PIs will use the records to (1) reconstruct atmospheric 14C/12C for the whole radiocarbon timescale (the last 45 ky) and (2) compare those records directly to the climate records from the same samples. The former will place constraints on the operation of the ocean-atmosphere carbon cycle since glacial times. The latter will characterize the interplay between changes in the carbon cycle and climate change. Both have implications for the understanding of the current and future carbon cycle. Recent work indicates extremely high and variable atmospheric 14C/12C for much of the interval between 44 and 34 Ka. The radiocarbon values are generally well above values that can be achieved with the modern carbon cycle, even if terrestrial and solar magnetic fields were negligible. These data therefore require significant differences between the modern and glacial carbon cycles, as well as large temporal changes in the glacial carbon cycle. The far-reaching implications of this work require replication, ideally at sites other than the Bahamas, the site where this evidence was collected.