Evaluating Sea-Surface Conditions in the Interglacial Arctic Ocean Using Planktic Foraminiferal Assemblages and Mg/Ca Ratios

使用浮游有孔虫组合和 Mg/Ca 比率评估间冰期北冰洋的海面条件

• 批准号: 1404370
• 负责人: Leonid Polyak
• 金额: $ 25.2万
• 依托单位: Ohio State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-07-01 至 2018-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1404370&HistoricalAwards=false
• 关键词: Evaluating; Sea; Surface; Conditions; Interglacial

Summer sea ice cover in the Arctic Ocean is diminishing rapidly. The rate and extent to which it decreases has implications for shipping, mineral development, climate, and national defense. Models can be used to predict the future with some accuracy, but we know that existing models cannot yet fully reproduce observed changes in sea ice extent. Another approach is to look for analogs in the past. What was the sea cover like in the geologic past? Was the Arctic ice free under previous warm atmospheric conditions? Using independent estimates such as from ice cores, it is known when the Arctic was warm in the past. This project will develop an estimator, or proxy, for sea surface temperature. This is based on single-celled organisms known as foraminifera that live in the surface waters of the ocean. When the proxy indicates that sea surface temperature was higher than the melting point of sea ice, we know that sea ice was not present.In the course of completing this research project, contributions will be made to training the next generation of scientists, as well as to informing the broader population about the Arctic. Partial support of a postdoctoral researcher on this project will allow her to broaden her scientific expertise and international experience. An undergraduate student involved in this work will also receive valuable training in many technical aspects of the research. Collaboration with scientists from several countries will aid in fostering broader international cooperation in the Arctic. Results of this research will enrich the content of courses taught by the principal investigator. Knowledge from this project will be disseminated to both specialists and the broader public through talks, publications in professional and popular journals, and internet blogs. The target audiences will include K-12 students of various grades, as well as parents and educators through the Byrd Polar Research Center Learning Center. Proxy reconstructions of the past warm intervals in the Arctic are needed to compare and contrast with understanding of the ongoing and projected changes in the Arctic marine ecosystem environment. Funds are provided to characterize Arctic paleo sea surface temperatures based on the composition of planktic foraminiferal species and their magnesium/calcium ratios in sediment samples from the Fram Strait (the Arctic-Atlantic gateway) and the central Arctic Ocean. This research will involve close collaboration with several national and international partners to ensure sample exchange, interlaboratory data compatibility, and a broad context for interpretation. Achieving the project goals involves several methodological and data-producing steps, including (1) development of the optimal cleaning/measuring procedure for Mg/Ca analysis on fragile tests of subpolar planktic foraminifers, (2) calibration of Mg/Ca to modern hydrography using improved assemblage-based transfer functions, and (3) reconstruction of paleo temperatures at high-resolution (decadal to century-scale) using Holocene cores from the Fram Strait, as well as warming/ice-reduction events in the central Arctic Ocean (e.g., Marine Isotope Stages 1, 5, and 11). This research will provide insights into the extent of surface warming and sea-ice retreat in the Arctic Ocean during past climate amelioration events, as well as the short-term variability in the export of sea ice and polar waters during the Holocene. It will also contribute to understanding the response of Arctic biota, exemplified by planktic foraminifers, to climatic warming and sea-ice reduction. The resultant data sets will be made available through appropriate public archives.

北冰洋夏季海冰覆盖面积正在迅速减少。它减少的速度和程度对航运、矿产开发、气候和国防都有影响。模式可以用来预测未来有一定的准确性，但我们知道，现有的模式还不能完全重现观测到的海冰范围的变化。另一种方法是寻找过去的相似之处。在过去的地质时期，海洋的覆盖是什么样的？在之前温暖的大气条件下，北极是无冰的吗？通过对冰芯的独立估计，我们可以知道北极在过去什么时候是温暖的。这个项目将开发一个海面温度的估算器或代理。这是基于被称为有孔虫的单细胞生物，它们生活在海洋的表层水域。当代用物表明海面温度高于海冰的熔点时，我们就知道海冰不存在。在完成这项研究项目的过程中，将为培训下一代科学家以及向更广泛的人群宣传北极做出贡献。对该项目的博士后研究员的部分支持将使她能够扩大她的科学专业知识和国际经验。参与这项工作的本科生也将在研究的许多技术方面得到宝贵的训练。与几个国家的科学家合作将有助于促进北极地区更广泛的国际合作。这项研究的结果将丰富首席研究员所教授的课程内容。从这个项目中获得的知识将通过讲座、专业和大众期刊的出版物以及互联网博客传播给专家和更广泛的公众。目标受众将包括K-12年级的各个年级的学生，以及通过伯德极地研究中心学习中心的家长和教育工作者。北极过去暖期的替代重建需要与对北极海洋生态系统环境正在发生的和预计的变化的理解进行比较和对比。根据来自弗拉姆海峡（北极-大西洋门户）和北冰洋中部的沉积物样品中浮游有孔虫物种的组成及其镁/钙比率，提供了资金来表征北极古海面温度。这项研究将涉及与几个国家和国际伙伴的密切合作，以确保样品交换、实验室间数据兼容性和广泛的解释背景。实现项目目标涉及几个方法学和数据生成步骤，包括：(1)开发用于亚极地浮游有孔虫脆弱测试中Mg/Ca分析的最佳清洗/测量程序，(2)使用改进的基于组合的传递函数将Mg/Ca校准为现代水文，以及(3)使用Fram海峡全新世岩心以高分辨率（年代际到世纪尺度）重建古温度。以及北冰洋中部的变暖/冰减少事件（例如，海洋同位素阶段1、5和11）。这项研究将深入了解过去气候改善事件期间北冰洋表面变暖和海冰退缩的程度，以及全新世期间海冰和极地水域输出的短期变化。它还将有助于了解以浮游有孔虫为例的北极生物群对气候变暖和海冰减少的反应。所得的数据集将通过适当的公共档案提供。