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

北冰洋夏季海冰覆盖面积正在迅速减少。下降的速度和程度对航运、矿产开发、气候和国防都有影响。模型可以用来预测未来，具有一定的准确性，但我们知道，现有的模型还不能完全再现观测到的海冰面积的变化。另一种方法是寻找过去的类似之处。过去的地质时期，海面是什么样子的？在以前温暖的大气条件下，北极的冰是自由的吗？使用独立的估计，如从冰芯，这是已知的时候北极在过去是温暖的。该项目将开发海洋表面温度的估计器或替代物。这是基于生活在海洋表层水域的被称为有孔虫的单细胞生物。当代理表明海面温度高于海冰的融点时，我们就知道海冰不存在。在完成这一研究项目的过程中，将为培养下一代科学家以及向更广泛的民众宣传北极做出贡献。对该项目博士后研究人员的部分支持将使她能够扩大她的科学专长和国际经验。参与这项工作的本科生还将在研究的许多技术方面接受有价值的培训。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。本研究的成果将丰富首席调查员的教学内容。该项目的知识将通过讲座、专业和流行期刊上的出版物以及互联网博客向专家和更广泛的公众传播。目标受众将包括不同年级的K-12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。需要对北极过去的温暖时段进行替代重建，以便与对北极海洋生态系统环境正在发生和预计发生的变化的理解进行比较和对比。提供资金，根据弗拉姆海峡(北极-大西洋门户)和北冰洋中部沉积物样本中浮游有孔虫物种的组成及其镁/钙比，确定北极古海洋表面温度。这项研究将涉及与几个国家和国际伙伴的密切合作，以确保样本交换、实验室间数据兼容性和广泛的解释背景。实现项目目标涉及若干方法学和编制数据的步骤，包括：(1)制定关于亚极地浮游有孔虫脆弱测试的镁/钙分析的最佳清洁/测量程序；(2)利用改进的基于组合的传递函数将镁/钙与现代水文学进行校准；(3)利用来自弗拉姆海峡的全新世岩心重建高分辨率(十年至世纪尺度)的古温度，以及北冰洋中部的变暖/减冰事件(如海洋同位素第1、5和11阶段)。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消退的程度，以及全新世期间海冰和极地水域出口的短期变化。它还将有助于理解以浮游有孔虫为代表的北极生物群对气候变暖和海冰减少的反应。由此产生的数据集将通过适当的公共档案提供。

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.