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

这项研究将检验最重要的假设，即在最后一次冰川消融期间，南大洋的通风导致低D14C的水通过南极中间水(AAIW)分两个阶段向北扩散。这项工作是在下加利福尼亚州南端附近最近的结果基础上进行的，这些结果显示，在两次去冰期大气二氧化碳增加(大气D14C减少)期间，中间水D14C都急剧下降；这样的观测似乎需要从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CO2以及海洋和大气D14C的既定消冰变化联系在一起。研究基于下加利福尼亚州南部大陆边缘和智利南部边缘沉积岩芯深度横断面的底水和地表水D14C重建。D14C的重建是根据沉积物中底栖和浮游有孔虫的14C测量得出的，并具有独立的气候-地层年龄控制。这项研究增加了对海洋在冰川-间冰期大气二氧化碳循环中作用的机械理解，并为用于预测未来变化的海洋-大气数值模型的测试提供了具体的目标。该项目还为一名博士生和一名地质科学本科生提供广泛的培训。

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.