Collaborative Research: Bringing the Late Pleistocene into Focus: Better Estimates of Ages and Ocean Circulation Through Data-Model Comparison

合作研究：关注更新世晚期：通过数据模型比较更好地估计年龄和海洋环流

• 批准号: 1760958
• 负责人: Geoffrey Gebbie
• 金额: $ 14.64万
• 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: 2018
• 资助国家: 美国
• 起止时间: 2018-04-01 至 2021-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1760958&HistoricalAwards=false
• 关键词: Collaborative; Research; Bringing; Late; Pleistocene

Measurements of past climate changes are crucial for understanding the causes, amplitudes, and rates of natural climate variability. Ocean sediments contain abundant microfossils that are an important archive of past climate information with near-global coverage. To place an ocean sediment sample into context, researchers need two kinds of information: (1) an interpretation of the climate represented by that sample and (2) the age of the sample. Age information is crucial for reconstructing the rate and sequence of climate changes globally. Some sediments are well-dated using radiocarbon. However, the ages of many samples can only be estimated indirectly, resulting in age uncertainties as large as 4,000 years. This research project aims to improve these indirect age estimates using statistical analysis of the available radiocarbon-dated samples. Improvements in indirect age estimates will be used to increase the accuracy of global datasets of climate changes for the past 150,000 years.More specifically, the aim of this project is to improve indirect age estimates derived from the stratigraphic alignment of benthic delta18O (a proxy for global ice volume and deep ocean temperature). A major source of uncertainty in these ages derives from differences of up to 4,000 years in the timing of benthic delta18O change observed at a few core sites with very accurate radiocarbon models. However, little is known about how the timing of benthic delta18O signals differs at other locations. The research approach for this project incorporates ocean circulation models, paleoclimate data (benthic delta18O and 14C from ~100 globally distributed sediment cores), and statistical inference. Phase one of the project is to characterize benthic delta18O age differences (delta18O lags) globally using radiocarbon data from ~100 sediment cores in conjunction with results from ocean circulation models. Phase two is to apply the results from phase one to develop improved methods for delta18O alignment. Phase three is to generate a new database of improved delta18O age models. Thus, the final products of the project will be (1) probabilistic stacks (averages) describing regional and global patterns of benthic delta18O variability, (2) probabilistic algorithms for multiproxy core alignments and for generating Bayesian inferences of delta18O lags, (3) a database of age models for ~300 cores with benthic delta18O data, and (4) estimates of ocean circulation changes based on comparing benthic del18O data with different circulation model scenarios.This project has broader impacts for climate change research and education. Accurate paleoclimate age estimates are crucial for creating data compilations that are used to test the effectiveness of climate models and improve confidence in their ability to simulate potential future climate changes. The spatial coverage of paleoclimate data compilations is often increased by including data with indirect age estimates that have large uncertainties. By improving age estimates for benthic delta18O alignments and quantifying alignment age uncertainties, this project will allow for more informed selection of which data to include in compilations and overall better accuracy. Data-model comparison performed as part of this project will also better constrain ocean circulation changes, which could help describe the causal chain of events for past climate changes and may identify isolated reservoirs of carbon sequestered in the ocean during glaciations. This project will also provide interdisciplinary training in earth science and mathematics to two graduate students. Research methods and findings will be incorporated into undergraduate and graduate classes through the development and dissemination of interactive computer lab activities.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.

过去气候变化的测量对于理解自然气候变化的原因，幅度和速率至关重要。海洋沉积物中包含丰富的微化石，这是过去气候信息的重要档案，并具有近乎全球的覆盖范围。要将海洋沉积物样本置于上下文中，研究人员需要两种信息：（1）对该样本代表的气候的解释以及（2）样本的年龄。年龄信息对于重建全球气候变化的速度和序列至关重要。一些沉积物使用放射性碳良好。但是，许多样本的年龄只能间接估计，从而导致年龄不确定性长达4000年。该研究项目旨在使用可用的放射性碳日期样本的统计分析来改善这些间接年龄估计。间接年龄估计的改善将用于提高过去150,000年的气候变化全球数据集的准确性。更具体地说，该项目的目的是改善底栖底迪（Benthic delta18o）地层比对得出的间接年龄估计值（全球冰量和深海温度的代理）。在这些年龄段的主要不确定性来源是在底栖三角洲18o变化时的差异最高4，000年，这些变化在几个具有非常准确的放射性碳模型的核心地点观察到。但是，关于底栖delta18o信号的时间在其他位置有何不同，知之甚少。该项目的研究方法结合了海洋循环模型，古气候数据（底栖三角洲18O和14C的全球分布沉积物核心）和统计推断。该项目的第一阶段是使用来自〜100个沉积物核心的放射性碳数据以及海洋循环模型的结果来表征全球底栖delta18o年龄差异（Delta18o滞后）。第二阶段是应用第一阶段的结果来开发改进的Delta18O比对方法。第三阶段是生成改进的Delta18O年龄模型的新数据库。 Thus, the final products of the project will be (1) probabilistic stacks (averages) describing regional and global patterns of benthic delta18O variability, (2) probabilistic algorithms for multiproxy core alignments and for generating Bayesian inferences of delta18O lags, (3) a database of age models for ~300 cores with benthic delta18O data, and （4）基于比较底栖del18O数据与不同循环模型方案的估计变化的估计。该项目对气候变化研究和教育产生了更大的影响。准确的古气候年龄估计值对于创建用于测试气候模型有效性的数据汇编至关重要，并提高对模拟未来气候变化的能力的信心。通过包括具有较大不确定性的间接年龄估计的数据，通常增加了古气候数据汇编的空间覆盖范围。通过改善底栖三角洲18O对准的年龄估计并量化对齐年龄不确定性，该项目将允许更明智地选择哪些数据包含在汇编中和整体上更好的准确性。作为该项目的一部分进行的数据模型比较还将更好地限制海洋循环的变化，这可以帮助描述过去气候变化的事件的因果关系链，并可以在冰川期间识别出海洋中隔离的碳含量。该项目还将为两名研究生提供地球科学和数学的跨学科培训。通过开发和传播交互式计算机实验室活动，研究方法和发现将被纳入本科和研究生班。该奖项反映了NSF的法定任务，并被认为是值得通过基金会的知识分子和更广泛影响的评估评估标准来通过评估来支持的。