Collaborative Proposal: Miocene Climate Extremes: A Ross Sea Perspective from IODP Expedition 374 and DSDP Leg 28 Marine Sediments

合作提案：中新世极端气候：IODP 374 号探险队和 DSDP 第 28 段海洋沉积物的罗斯海视角

• 批准号: 1947646
• 负责人: Amelia Shevenell
• 金额: $ 43.45万
• 依托单位: University of South Florida
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2020
• 资助国家: 美国
• 起止时间: 2020-05-01 至 2025-04-30
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1947646&HistoricalAwards=false
• 关键词: Collaborative; Proposal; Miocene; Climate; Extremes

Nontechnical abstractPresently, Antarctica’s glaciers are melting as Earth’s atmosphere and the Southern Ocean warm. Not much is known about how Antarctica’s ice sheets might respond to ongoing and future warming, but such knowledge is important because Antarctica’s ice sheets might raise global sea levels significantly with continued melting. Over time, mud accumulates on the sea floor around Antarctica that is composed of the skeletons and debris of microscopic marine organisms and sediment from the adjacent continent. As this mud is deposited, it creates a record of past environmental and ecological changes, including ocean depth, glacier advance and retreat, ocean temperature, ocean circulation, marine ecosystems, ocean chemistry, and continental weathering. Scientists interested in understanding how Antarctica’s glaciers and ice sheets might respond to ongoing warming can use a variety of physical, biological, and chemical analyses of these mud archives to determine how long ago the mud was deposited and how the ice sheets, oceans, and marine ecosystems responded during intervals in the past when Earth’s climate was warmer. In this project, researchers from the University of South Florida, University of Massachusetts, and Northern Illinois University will reconstruct the depth, ocean temperature, weathering and nutrient input, and marine ecosystems in the central Ross Sea from ~17 to 13 million years ago, when the warm Miocene Climate Optimum transitioned to a cooler interval with more extensive ice sheets. Record will be generated from new sediments recovered during the International Ocean Discovery Program (IODP) Expedition 374 and legacy sequences recovered in the 1970’s during the Deep Sea Drilling Program. Results will be integrated into ice sheet and climate models to improve the accuracy of predictions. The research provides experience for three graduate students and seven undergraduate students via a multi-institutional REU program focused on increasing diversity in Antarctic Earth Sciences. Technical AbstractDeep-sea sediments reveal that the Miocene Climatic Optimum (MCO) was the warmest climate interval of the last ~20 Ma, was associated with global carbon cycle changes and ice growth, and immediately preceded the Middle Miocene Climate Transition (MMCT; ~14 Ma), one of three major intervals of Antarctic ice expansion and global cooling. Ice-proximal studies are required to assess: where and when ice grew, ice sheet extent, continental shelf geometry, high-latitude heat and moisture supply, oceanic and/or atmospheric temperature influence on ice dynamics, regional sea ice extent, meltwater input, and regions of bottom water formation. Existing studies indicate that ice expanded beyond the Transantarctic Mountains and onto the prograding Ross Sea continental shelf multiple times between ~17 and 13.5 Ma. However, these records are either too ice-proximal/terrestrial to adequately assess ocean-ice interactions or under-studied. To address this data gap, this work will: 1) generate micropaleontologic and geochemical records of oceanic and atmospheric temperature, water depth, ocean circulation, and paleoproductivity from existing Ross Sea marine sedimentary sequences, and 2) use these proxy records to test the hypothesis that dynamic glacial expansion in the Ross Sea sector during the MCO was driven by heat and moisture transport to the high latitudes during an interval of enhanced climate sensitivity. Downcore geochemical and micropaleontologic studies will focus on an expanded (120 m/my) early to middle Miocene (~17-16 Ma) diatom-bearing/rich mudstone/diatomite unit from IODP Site U1521, drilled on the Ross Sea continental shelf. A hiatus (~16-14.6 Ma) suggests ice expansion during the MCO, followed by diamictite to mudstone unit indicative of slight retreat (14.6 -14 Ma) immediately preceding the MMCT. Data from Site U1521 will be integrated with foraminiferal geochemical and micropaleontologic data from DSDP Leg 28 (1972/73) and RISP J-9 (1978-79) to develop a MCO to late Miocene regional view of ocean-ice sheet interactions using legacy core material previously processed for foraminifera. This integrated record will: 1) document the timing and extent of glacial advances and retreats across the prograding Ross Sea shelf during the middle and late Miocene, 2) provide orbital-scale paleotemperature reconstructions (TEX86, Mg/Ca, δ18O, MBT/CBT) to establish atmosphere-ocean-ice interactions during an extreme high-latitude warm interval, and 3) provide orbital-scale nutrient/paleoproductivity, ocean circulation, and paleoenvironmental data required to assess climate feedbacks associated with Miocene Antarctic ice sheet and global climate system development.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

目前，随着地球大气层和南大洋的变暖，南极洲的冰川正在融化。关于南极洲的冰盖如何应对持续和未来的变暖，我们所知不多，但这些知识很重要，因为南极洲的冰盖可能会随着持续融化而显著提高全球海平面。随着时间的推移，泥浆在南极洲周围的海底积累，这些泥浆由微生物的骨骼和碎片以及邻近大陆的沉积物组成。随着这些泥浆的沉积，它创造了过去环境和生态变化的记录，包括海洋深度，冰川进退，海洋温度，海洋环流，海洋生态系统，海洋化学和大陆风化。有兴趣了解南极洲的冰川和冰盖如何应对持续变暖的科学家可以使用这些泥浆档案的各种物理，生物和化学分析来确定泥浆沉积的时间以及冰盖，海洋和海洋生态系统如何在过去地球气候变暖的间隔期间做出反应。在这个项目中，来自南佛罗里达大学，马萨诸塞州大学和北方伊利诺伊大学的研究人员将重建深度，海洋温度，风化和营养输入，以及罗斯海中部的海洋生态系统，从大约1700万年到1300万年前，当温暖的中新世气候最佳过渡到更广泛的冰盖的较冷间隔。记录将产生于国际海洋发现计划（IODP）374远征期间恢复的新沉积物和20世纪70年代深海钻探计划期间恢复的遗留序列。结果将被纳入冰盖和气候模型，以提高预测的准确性。该研究通过多机构REU计划为三名研究生和七名本科生提供经验，该计划专注于增加南极地球科学的多样性。深海沉积物显示中新世气候适宜期（MCO）是近20 Ma以来最温暖的气候时段，与全球碳循环变化和冰的生长有关，并紧接着中中新世气候转换期（MMCT; ~14 Ma），这是南极冰扩张和全球变冷的三个主要时段之一。需要对近冰区进行研究，以评估：冰生长的地点和时间、冰盖范围、大陆架几何形状、高纬度热量和水分供应、海洋和/或大气温度对冰动态的影响、区域海冰范围、融水输入和底层水形成区域。现有的研究表明，在~17和13.5 Ma之间，冰多次扩展到跨南极山脉之外，并进入罗斯海大陆架。然而，这些记录要么太接近冰/陆地，以充分评估海洋-冰的相互作用或研究不足。为了解决这一数据差距，这项工作将：1）从现有罗斯海海洋沉积序列中产生海洋和大气温度、水深、海洋环流和古生产力的微体古生物和地球化学记录，和2）利用这些代用记录来检验这一假设，即MCO期间罗斯海地区的动态冰川扩张是由在一次大冰期期间向高纬度地区输送的热量和水分驱动的。气候敏感性增强的时间间隔。深钻地球化学和微体古生物学研究将侧重于在罗斯海大陆架钻探的IODP站点U1521的早中新世至中中新世（~17-16 Ma）含碳酸盐/富碳酸盐泥岩/碳酸盐单元的扩展（120 m/my）。一个间断（~16-14.6 Ma）表明MCO期间冰膨胀，随后是杂岩到泥岩单元，表明紧接在MMCT之前的轻微后退（14.6 - 14 Ma）。来自站点U1521的数据将与来自DSDP第28航次（1972/73年）和RISP J-9（1978-79年）的有孔虫地球化学和微体古生物学数据相结合，以使用先前处理过的有孔虫遗留岩心材料，开发海洋-冰盖相互作用的MCO至晚中新世区域视图。这一综合记录将：1）记录中新世中晚期罗斯海陆架冰川进退的时间和范围，2）提供轨道尺度的古温度重建（TEX 86，Mg/Ca，δ 18 O，MBT/CBT）建立极端高纬暖期大气-海洋-冰相互作用; 3）提供轨道尺度的营养/古生产力、海洋环流、该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。