Antarctic Intermediate Water Ventilation Through the Last Deglaciation Off Chile

OCE-0751643从末次盛冰期到全新世气候转变的最重要和无法解释的观测之一是大气中CO2含量的突然上升和大气中放射性碳（14 C）含量的同时减少，大约在16，000年前开始。 有人假设，这些变化反映了深海环流的突然变化，因为海洋是比大气大得多的碳储存库。深海-大气层联系的最有力证据来自Marchitto等人的一项研究，（2007年）的研究表明，从16,000年前开始，下加利福尼亚的底栖有孔虫化石的放射性碳含量急剧下降。他们假设这些数据反映了从南大洋深处到北太平洋的“旧”碳的运输。在该项目中，PI将确认这些已发表的结果，并通过研究智利边缘沿着一个深度断面的一套沉积物岩心中的底栖和南极有孔虫化石的放射性碳含量，检验冰消期大气CO2增加是由于南极中层水向南大洋深层释气所致的假设。 由于这一区域非常接近旧深水的假定南大洋来源，并且岩心跨越一系列中间海洋水深，因此它们是测试下加利福尼亚观测和假设的理想选择。 PI将为智利岩心套制定氧同位素地层学和年代学，以确定冰消期间隔，并将测量岩心中底栖有孔虫的放射性碳，以确定冰消期期间放射性碳通风变化的深度范围和程度。 这项研究的结果将测试不断发展的理论的一个重要组成部分，以解释陆地，海洋和大气在冰川消退期间如何相互作用，以改变全球气候。更广泛的影响将包括基础研究，以帮助解释过去气候变化的机制，K-12推广和智利博士后研究员里卡多·德波尔·霍尔茨博士的国际指导。

OCE-0751643One of the most important and unexplained observations of the climate transition from the Last Glacial Maximum into the Holocene is the abrupt rise in atmospheric CO2 content and coincident decrease in the atmosphere's radiocarbon (14C) content that began about 16,000 years ago. It has been hypothesized that these changes reflect a sudden change in deep ocean circulation because the ocean is a much larger reservoir of carbon than the atmosphere. The strongest evidence for a deep ocean-atmosphere connection comes from a study by Marchitto et al., (2007) that showed the radiocarbon content of fossil benthic foraminifera from Baja California decreased dramatically starting 16,000 years ago. They hypothesized these data reflect the transit of 'old' carbon from the deep Southern Ocean to the north Pacific. In this project, the PI will confirm these published results and test the hypothesis that the increase in deglacial atmospheric CO2 was due to outgasing of the deep Southern Ocean via Antarctic Intermediate Water by studying the radiocarbon content of fossil benthic and planktic foraminifera in a suite of sediment cores along a depth transect from the Chilean margin. Because this region is very close to the presumed Southern Ocean source of the old deep water, and the cores span a range of intermediate ocean water depths, they are ideal for testing the Baja California observations and hypotheses. The PI will develop oxygen isotope stratigraphies and chronologies for the Chilean core suite to identify the deglacial interval, and will measure radiocarbon in benthic foraminifera from the cores to define the depth range and the extent of the radiocarbon ventilation changes during the deglaciation. The results of this research will test an important component of the evolving theory to explain how the land, the sea and the atmosphere interacted during the deglaciation to alter global climate. Broader impacts will include fundamental research to help explain the mechanisms of past climate change, K-12 outreach and international mentoring of a Chilean postdoctoral fellow, Dr. Ricardo dePol Holz.