Collaborative Research: Vertical gradients in Southern Ocean Radiocarbon across the major climate transitions of the last 30,000 years

合作研究：过去 3 万年主要气候转变期间南大洋放射性碳的垂直梯度

• 批准号: 1903723
• 负责人: Christopher Charles
• 金额: $ 20.79万
• 依托单位: University of California-San Diego Scripps Inst of Oceanography
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2019
• 资助国家: 美国
• 起止时间: 2019-09-01 至 2023-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1903723&HistoricalAwards=false
• 关键词: Collaborative; Research; Vertical; gradients; Southern

The Southern Ocean holds disproportionate influence in setting atmospheric CO2 variability and carbon storage in the deep ocean because it is a region featuring both upwelling and deep-water formation. Consequently, considerable effort has been devoted to understanding the Southern Ocean conditions and processes that ultimately led to lower atmospheric CO2 during the last ice age. Radiocarbon is in principle the most diagnostic tracer for ocean/atmosphere carbon cycling over this time period. However, the existing body of radiocarbon data for the Southern Ocean is still limited temporally and spatially, while also suffering from some essential uncertainties that preclude firm conclusions about carbon cycling during the last ice age. This project involves a coordinated program of radiocarbon measurements in three distinct archives of Southern Ocean oceanographic change that span the last 30,000 years. These archives, including both marine sediment sequences and deep-sea coral samples, are located so as to capture the surface, intermediate and deep-water carbon cycle response to climate forcing. The objective of this program is to extend existing radiocarbon measurements while also directly resolving some of the principal uncertainties that currently limit the application of existing radiocarbon observations. The program will serve as a natural platform for engagement of underrepresented students to STEM disciplines and will include undergraduate and masters-level students recruited from local community colleges and state universities.More specifically, the project includes i.) planktonic-benthic foraminiferal radiocarbon age measurements in a newly acquired sediment sequence off Mozambique (IODP Site U1477) that features exceptionally high resolution; the bottom water at this location is recently ventilated water subducted just south of the Subtropical Convergence, and, therefore, the benthic foraminiferal radiocarbon variability monitors that of the sub-Antarctic surface ocean; ii.) U-series/radiocarbon age pairs in a set of deep-sea coral samples collected from intermediate water depths off Tasmania; the radiocarbon variability expressed in this series of samples is intended as a direct comparison to that of the Mozambique foraminiferal sequence; iii.) extension of existing (but not yet definitive) planktonic-benthic foraminiferal age depth pairs in abyssal South Atlantic sedimentary sequences; the benthic foraminiferal radiocarbon variability at these sites should reflect the deep branch of the Meridional Overturning Circulation (MOC). The intention is to provide new observations that, both on their own and by unlocking the potential of existing measurements, will serve as direct tests of models of the relationship between climate forcing and carbon cycling.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

南部海洋在将大气中的二氧化碳变异性和深海中的碳储存设置为含量中占不成比例的影响，因为它是一个具有上升和深水形成的地区。 因此，已经大力致力于理解南部海洋状况和过程，这些条件和过程最终导致了最后一个冰河时代大气中的二氧化碳。放射性碳原则上是在这段时间内海洋/大气碳循环的最诊断示踪剂。但是，现有的南大洋的放射性碳数据在时间和空间上仍然受到限制，同时还遭受了一些基本不确定性，这些不确定性排除了最后一个冰河时代的碳循环结论。该项目涉及在过去30，000年的三个不同的南海海洋学变化档案中协调的放射性碳测量计划。这些档案，包括海洋沉积物序列和深海珊瑚样品，以捕获表面，中间和深水碳循环对气候强迫的反应。该计划的目的是扩展现有的放射性碳测量结果，同时还直接解决了一些当前限制现有放射性碳观察的主要不确定性。 The program will serve as a natural platform for engagement of underrepresented students to STEM disciplines and will include undergraduate and masters-level students recruited from local community colleges and state universities.More specifically, the project includes i.) planktonic-benthic foraminiferal radiocarbon age measurements in a newly acquired sediment sequence off Mozambique (IODP Site U1477) that features exceptionally high resolution;最近在亚热带收敛以南的通风水俯冲，因此是底栖有孔虫放射性碳变异性监测器的底部水。 ii。）U系列/放射性碳年龄对，一组从塔斯马尼亚州中间水深收集的深海珊瑚样品；在这一系列样品中表达的放射性碳变异旨在与莫桑比克有孔虫序列的放射性变异性直接比较。 iii。）在深渊南大西洋沉积物序列中现有（但尚未确定的）浮游有孔虫年龄深度对扩展；这些位点的底栖有孔虫放射性碳变异性应反映子午倾覆循环（MOC）的深部分支。目的是提供新的观察结果，无论是自己还是通过释放现有测量的潜力，将作为对气候强迫和碳循环之间关系模型的直接测试。该奖项反映了NSF的法定任务，并认为通过基金会的智力和更广泛的影响，可以通过评估来进行评估，以审查CRITERIA。