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

夏季北冰洋的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重现观测到的海冰范围的变化。 另一种方法是寻找过去的类似物。 在地质学上，过去的海洋是什么样的？ 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，它是已知的，当北极是温暖的过去。 该项目将开发一个海洋表面温度的估算器或代用品。 这是基于单细胞生物有孔虫，生活在海洋表面的沃茨。 当代用指标显示海面温度高于海冰的熔点时，我们就知道海冰并不存在，在完成这一研究项目的过程中，将有助于培训下一代科学家，并向更广泛的人口宣传北极。 该项目的博士后研究人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接受宝贵的培训。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研究员教授的课程内容。 该项目的知识将通过讲座、在专业和大众期刊上发表文章以及互联网博客传播给专家和广大公众。目标受众将包括各个年级的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。需要重建北极过去温暖时期的代用品，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。根据弗拉姆海峡（北极-大西洋门户）和北冰洋中部沉积物样品中北极有孔虫物种的组成及其镁/钙比率，提供资金以确定北极古海面温度的特征。这项研究将涉及与几个国家和国际合作伙伴的密切合作，以确保样本交换，实验室间数据的兼容性和广泛的解释背景。实现项目目标涉及若干方法和数据生成步骤，包括：（1）为亚极地南极有孔虫脆弱试验的Mg/Ca分析制定最佳清洁/测量程序;（2）使用改进的组合传递函数，根据现代水文学校准Mg/Ca;高分辨率古温度重建（十年到世纪尺度），使用来自弗拉姆海峡的全新世岩心，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沃茨出口的短期变化。它还将有助于了解北极生物群，例如北极有孔虫，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.