Biogeochemical linkages between Ice Age climate, ocean productivity, and carbon cycling

这项研究计划的目标是通过从沉积记录中存档的古环境指标重建过去的海洋条件，来探索海洋环流、海洋生产力和碳(C)循环之间的联系。提出了三个将采用相同方法的补充项目：将在东南太平洋深海岩心上生成新的生物通量、海表面温度和模态水替代数据，选择这些数据是因为它们对研究问题具有战略重要性，以及它们有能力填补现有知识的空白。这些新数据将放在正在进行的全球生物源通量数据综合的背景下，其中纳入了关于碳积累和海洋浮游植物丰度变化的七个指标的信息，以重建海洋生产力不同组成部分变化的相对时间。最后，这些数据将被用来评估精心设计的模型敏感性实验，在这些实验中，海冰覆盖、铁肥、上升流强度和淡水强迫都发生了变化。将把模拟的生产力变化与观测到的冰期重建进行比较，以评估哪些过程与下列项目的数据最匹配：项目1探索海冰覆盖和尘埃对二氧化硅和碳循环的影响。项目2研究了南半球环流变化(例如，西风、海洋锋面、亚南极模式水形成)对生产力的影响。项目3调查了从最后一个冰河时代到今天的过渡期间极地表面清新和相关的环流变化对海洋生产力的潜在影响。这项拟议的研究将对上一次冰河时代东南太平洋过去的海洋状况提供新的重建。全球古环境数据集为分析海洋生物地球化学模型模拟提供了广泛和高度新颖的评估工具，从而使地球系统科学领域受益。这些结果将有助于我们目前对冰河时代海洋C循环的了解，确定导致冰河时代大气二氧化碳变化的海洋机制。

The goal of this research program is to explore the linkages between ocean circulation, marine productivity, and carbon (C) cycling by reconstructing past ocean conditions from paleo-environmental indicators archived in the sedimentary record. Three complementary projects are proposed that will follow the same approach: New biogenic flux, sea-surface temperature, and mode-water proxy data will be generated on deep-sea cores from the southeast (SE) Pacific Ocean, selected for their strategic importance to the research questions and their ability to fill a gap in current knowledge. These new data will be placed within the context of an ongoing global biogenic flux data synthesis that incorporates information on seven indicators of changes in C accumulation and marine phytoplankton abundance, to reconstruct the relative timing of changes in different components of marine productivity. Finally, these data will be used to evaluate carefully designed model sensitivity experiments in which changes in sea-ice cover, iron fertilization, upwelling intensity, and freshwater forcing have been imposed. Simulated changes in productivity will be compared with observed ice age reconstructions to assess which processes provide the best match to the data for the following projects: PROJECT 1 explores the influence of sea-ice cover and dust on silica and C cycling. PROJECT 2 examines the influence of changed Southern Hemisphere circulation (e.g., westerly winds, oceanic fronts, Subantarctic Mode Water formation) on productivity. PROJECT 3 investigates the potential influence of polar surface freshening and associated circulation changes on marine productivity during the transition from the last Ice Age to today. The proposed research will provide new reconstructions of past oceanic conditions in the SE Pacific Ocean during the last Ice Age. The global paleo-environmental datasets benefit the field of Earth System science by providing extensive and highly novel evaluation tools for analyzing ocean biogeochemistry model simulations. The results will contribute to our current knowledge of the ice age ocean C cycle, identifying oceanic mechanisms responsible for ice-age changes in atmospheric carbon dioxide.