Tracing the Radiocarbon Signal of the Ocean's CO2 Release During the Last Deglaciation

本研究将验证南大洋通风导致低d14c水在末次冰消期的两个阶段通过南极中间水（AAIW）向北扩散的总体假设。这项研究是在加利福尼亚南部最近的研究结果的基础上进行的，该结果表明，在两次冰期大气二氧化碳增加（大气D14C减少）期间，中间水的D14C急剧下降；这样的观察似乎需要从一个假定的深海水库注入非常古老的水。这项工作将提供关键的机械证据，将海洋环流、大气二氧化碳、海洋和大气D14C等已建立的冰川消融变化联系起来。研究的基础是海底和地表水的D14C重建，这些重建来自下加利福尼亚州南部大陆边缘和智利南部边缘的沉积物岩心的深度样带。D14C的重建来源于沉积物中底栖生物和浮游有孔虫的14C测量，具有独立的气候-地层年龄控制。这项研究增加了对海洋在冰期-间冰期大气CO2循环中的作用的机制理解，并为用于预测未来变化的海洋-大气数值模式的测试提供了具体目标。该项目还为一名博士生和一名地质科学本科生提供了广泛的培训。

This research will test the overarching hypothesis that ventilation of the Southern Ocean caused low-D14C waters to spread northward via Antarctic Intermediate Water (AAIW) in two stages during the last deglaciation. The work follows on recent results from off the southern tip of Baja California that show dramatic drops in intermediate water D14C during each of the two deglacial atmospheric CO2 increases (atmospheric D14C decreases); such observations appear to require the injection of very old waters from a presumed abyssal reservoir.This work will provide crucial mechanistic evidence tying together established deglacial changes in ocean circulation, atmospheric CO2, and oceanic and atmospheric D14C. Studies are based on bottom- and surface- water D14C reconstructions in a depth transect of sediment cores from the continental margin off southern Baja California and from the southern Chilean Margin. D14C reconstructions are derived from benthic and planktic foraminiferal 14C measurements in sediments with independent climate-stratigraphic age control.This research adds to the mechanistic understanding of the ocean's role in glacial-interglacial atmospheric CO2 cycles and provides concrete targets for testing of ocean-atmosphere numerical models that are used to project future changes. The project also provides extensive training for a PhD student and a Geological Sciences undergraduate.