Antarctic Intermediate Water Ventilation Through the Last Deglaciation Off Chile

智利近海末次冰消期的南极中层水通风

• 批准号: 0751643
• 负责人: Lloyd Keigwin
• 金额: $ 30.91万
• 依托单位: Woods Hole Oceanographic Institution
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-05-01 至 2010-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0751643&HistoricalAwards=false
• 关键词: Antarctic; Intermediate; Water; Ventilation; Through

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.

关于从末次盛冰期到全新世的气候转变，最重要和最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（14C）含量的同时下降，这始于大约16000年前。据推测，这些变化反映了深海环流的突然变化，因为海洋是一个比大气大得多的碳储存库。深海与大气联系的最有力证据来自Marchitto等人（2007）的一项研究，该研究表明，从16000年前开始，下加利福尼亚州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“老”碳从南大洋深处到北太平洋的转移。在这个项目中，PI将通过研究智利边缘沿深度样带的一套沉积物岩心中的底栖生物和浮游有孔虫化石的放射性碳含量，来证实这些已发表的结果，并验证冰层融化大气中二氧化碳的增加是由于通过南极中间水向南大洋深处释放气体所致的假设。由于该地区非常接近假定的古老深水的南大洋来源，并且岩心跨越了一系列中等海洋水深，因此它们是检验下加利福尼亚观测和假设的理想选择。PI将为智利岩心组开发氧同位素地层学和年代学，以确定脱冰间隔，并将测量岩心底栖有孔虫中的放射性碳，以确定脱冰期间放射性碳通气变化的深度范围和程度。这项研究的结果将检验进化理论的一个重要组成部分，以解释在冰川消融期间陆地、海洋和大气如何相互作用，从而改变全球气候。更广泛的影响将包括帮助解释过去气候变化机制的基础研究，K-12推广和智利博士后Ricardo dePol Holz博士的国际指导。