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.

OCE-0751643从末次盛冰期到全新世的气候转变过程中最重要且无法解释的观测之一是大约 16,000 年前开始的大气中二氧化碳含量的突然上升和大气中放射性碳 (14C) 含量的同时下降。 据推测，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库。深海与大气之间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 16,000 年前开始，来自下加利福尼亚州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“旧”碳从南大洋深处到北太平洋的转移。在该项目中，项目负责人将通过研究沿着智利边缘深度横断面的一系列沉积物岩芯中底栖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，并检验以下假设：冰消期大气二氧化碳的增加是由于南大洋深处通过南极中层水的排气所致。 由于该区域非常接近推测的南大洋旧深水源头，并且岩芯跨越了一系列中等海水深度，因此非常适合测试下加利福尼亚州的观测和假设。 PI将为智利核心套件开发氧同位素地层学和年代学，以确定冰消期，并将测量岩心底栖有孔虫中的放射性碳，以确定冰消期期间的深度范围和放射性碳通气变化的程度。 这项研究的结果将测试演化理论的一个重要组成部分，以解释陆地、海洋和大气在冰消过程中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 推广以及智利博士后 Ricardo dePol Holz 博士的国际指导。