Investigating Geochemical Variability and Timing of Holocene Climatic Changes in Productivity and Terrigenous Input on the East Antarctic Margin

该奖项由极地项目办公室的南极地质与地球物理项目提供，为最近从东南极洲大陆架获得的海洋沉积物岩心的古海洋学和古气候研究提供资金。本研究的目的是通过对2001年初开展的全新世南极海洋沉积物（CHAOS）项目中恢复的超高分辨率沉积序列的地球化学研究，更好地了解南极东部边缘（EAM）的全新世气候变化。通过建立d15N、d13C、蛋白石、TOC和17种主要元素和微量元素的综合数据库，将开展一系列多样化的地球化学分析，提供养分利用、地表和出口生产、陆源通量和陆源物源指标。这个项目有两个相互加强的组成部分：波士顿大学的无机替代研究和斯坦福大学的互补同位素研究。这项工作将针对与南极东部边缘（EAM）在十年、百年和千年尺度上的气候变化有关的重要假设和问题，以及评估全球气候事件的影响，如小冰期、全新世气候最佳期、中世纪温暖期和新仙女木期。这项工作将比较和对比EAM（陆地冰盖）和南极半岛西部帕尔默深记录（主要是海洋冰盖）的记录。它将检查EAM， Palmer和北半球全新世记录之间事件的相对时间，并比较沿南极大陆边缘作用的生物（营养和出口）和物理（陆源）系统的气候变化的相对时间。综合生物和物理研究可以对南极海洋-陆地联合系统进行全面评估。通过无机化学手段记录出口生产的变化将是一种重要的独立方法，而不是研究人员专注于古生物记录（例如硅藻组合），并将提供有关大气CO2封存变化频率的定量信息。此外，氮同位素比值的变化既可以反映光区硝酸盐相对利用的差异，也可以用于跟踪深水和地表水之间的营养物质交换。碳同位素记录了水华事件，反映了地表水的生产力。各同位素指标（d15N、d13C、TOC、生物蛋白石、主微量元素等）响应生物地球化学循环的不同方面，只有综合它们才能更全面地反映该地区的系统情况。陆源通量和化学物源的变化可能表明EAM上基岩和土壤的风化模式、冰筏碎屑的输送、洋流的强度或边缘不同冰川制度的行为的变化。在其他研究的背景下解释这些结果将有助于评估当地冰川对气候变化和边缘降水的反应。这些问题已经用类似的方法和数据集的整合在南极半岛西部帕尔默深取得了巨大的成功。来自南极东部边缘的沉积物具有相当的分辨率和完整性，可用于将来比较南极东部冰盖和南极西部冰盖对气候变化的响应。

0126110MurrayThis award, provided by the Antarctic Geology and Geophysics Program of the Office of Polar Programs, provides funds for a paleoceanographic and paleoclimate study of recently acquired marine sediment cores from the continental shelf of East Antarctica. The goal of this work is to develop a better understanding of Holocene climate change on the East Antarctic Margin (EAM) via geochemical studies of ultra-high resolution sedimentary sequences recovered during the Coring Holocene Antarctic Ocean Sediments (CHAOS) program conducted in early 2001. A diverse suite of geochemical analyses will be carried out that will provide indicators of nutrient utilization, surface and export production, terrigenous flux, and terrigenous provenance by developing an integrated database of d15N, d13C, opal, TOC, and a diverse suite of 17 major and trace elements. This project has two mutually reinforcing components: inorganic proxy work at Boston University, and complementary isotopic studies at Stanford University. The work will target important hypotheses and questions relating to East Antarctic Margin (EAM) climate variability over decadal-, centennial-, and millennial-scale time scales, as well as assess the impact of global climatic events such as the Little Ice Age, Holocene climatic optimum, Medieval Warm Period, and Younger Dryas. This work will compare and contrast records from the EAM (a terrestrial ice sheet) to the Palmer Deep record off the West Antarctic Peninsula (a predominantly marine-based ice sheet). It will examine relative timing of events between the EAM, Palmer, and Northern Hemisphere Holocene records, and compare the relative timings of climatic change in both the biologic (nutrients and export) and physical (terrigenous) systems acting along the Antarctic continental margin. Integrating biological and physical studies allows for a comprehensive assessment of the combined marine-terrestrial Antarctic system. Documenting changes in export production through inorganic chemical means will be an important independent approach from that taken by researchers focusing on the paleontological record (e.g. diatom assemblages), and will provide quantitative information regarding the frequency of change in the sequestering of atmospheric CO2. In addition, variations in nitrogen isotope ratios can either reflect differences in relative utilization of nitrate in the photic zone or can be used to track the exchange of nutrients between deep and surface waters. Carbon isotope records track bloom events, which reflect productivity in the surface waters. Each of the isotope proxies (d15N, d13C, TOC, biogenic opal, major/trace elements, etc.) responds to different aspects of the biogeochemical cycle, and only by synthesizing them can a more complete picture of the region's systematics be achieved. Changes in the terrigenous flux and chemical provenance may indicate variations in the weathering patterns of bedrock and soil on the EAM, delivery of ice-rafted debris, the strength of ocean currents, or behavior of different glacial regimes on the margin. Interpreting these results within the context of other studies will allow an assessment of the response of local glaciers to changes in climate and precipitation on the margin. These issues have been targeted with similar methodologies and integration of data sets with great success in the Palmer Deep, West Antarctic Peninsula. The sediments from the East Antarctic Margin are of comparable resolution and integrity to allow for future comparisons of the response of both the East Antarctic Ice Sheet and West Antarctic Ice Sheet to climate change.