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: 1947558
• 负责人: R Leckie
• 金额: $ 35.21万
• 依托单位: University of Massachusetts Amherst
• 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 2024-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1947558&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.

非技术摘要目前，随着地球大气和南大洋变暖，南极洲的冰川正在融化。关于南极洲的冰盖可能如何应对目前和未来的变暖，我们知之甚少，但这样的知识很重要，因为随着冰盖的持续融化，南极洲的冰盖可能会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堆积，这些泥浆由微小海洋生物的骨骼和碎片以及来自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、海洋循环、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们可以利用对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了多久，以及在过去地球气候变暖的时候，冰盖、海洋和海洋生态系统是如何反应的。在这个项目中，来自南佛罗里达大学、马萨诸塞大学和北伊利诺伊大学的研究人员将重建约1700万年前到1300万年前罗斯海中部的深度、海洋温度、风化和营养输入以及海洋生态系统，当时温暖的中新世气候最佳时期过渡到更凉爽的时间段，有更大的冰盖。记录将产生于国际大洋发现计划第374次远征期间发现的新沉积物和1970年深海钻探计划期间S发现的遗留层序。结果将被整合到冰盖和气候模型中，以提高预测的准确性。这项研究通过一个多机构的REU项目为三名研究生和七名本科生提供了经验，该项目的重点是增加南极地球科学的多样性。深海沉积物显示，中新世气候最佳时期(MCO)是近20 Ma以来最温暖的气候时期，与全球碳循环变化和冰的生长有关，紧接在南极冰扩张和全球变冷的三个主要时期之一的中中新世气候转变(MMCT；~14 Ma)之前。需要对冰层附近进行研究，以评估：冰在哪里和何时生长、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)大气温度对冰动力学的影响、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 Ma到13.5 Ma之间，冰多次扩展到横贯北极山脉的罗斯海大陆架上。然而，这些记录要么过于接近冰层/陆地，无法充分评估海冰相互作用，要么研究不足。为了解决这一数据缺口，这项工作将：1)从现有的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古生物和地球化学记录，以及2)利用这些替代记录来检验这样一个假设，即在MCO期间，罗斯海地区的冰川动态扩张是由气候敏感性增强期间向高纬度输送的热量和水分驱动的。下部岩心的地球化学和微古生物研究将集中在罗斯海大陆架上IODP站点U1521的早至中新世(~17-16 Ma)扩大的(120m/m)硅藻/富泥岩/硅藻土单元。其间歇期(~16-14.6 Ma)指示MCO期间冰的扩张，随后是硅质岩-泥岩单元的轻微退缩(14.6-14 Ma)，紧接着MMCT。来自U1521站的数据将与来自DSDP LEG 28(1972/73)和RISP J-9(1978-79)的有孔虫地球化学和微古生物数据相结合，以利用先前为有孔虫处理的遗留岩芯材料，开发MCO至晚中新世海洋-冰盖相互作用的区域视图。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程度；2)提供轨道尺度的古温度重建(TEX86、镁/钙、δ18O、MBT/CBT)，以建立极高纬度变暖期间的大气-海洋-冰相互作用；3)提供轨道尺度的营养物质/古生产力、海洋环流和古环境数据，以评估与中新世南极冰盖和全球气候系统发展相关的气候反馈。该奖项反映了美国国家科学基金会的法定使命，通过使用基金会的智力优势和更广泛的审查标准进行评估，认为值得支持。

项目成果

Early and middle Miocene ice sheet dynamics in the Ross Sea: Results from integrated core-log-seismic interpretation

罗斯海早中新世冰盖动力学：岩心-测井-地震综合解释的结果

• DOI: 10.1130/b35814.1
• 发表时间: 2021
• 期刊: GSA Bulletin
• 作者: Pérez, Lara F.;Santis, Laura De;McKay, Robert M.;Larter, Robert D.;Ash, Jeanine;Bart, Phil J.;Böhm, Gualtiero;Brancatelli, Giuseppe;Browne, Imogen;Colleoni, Florence
• 通讯作者: Colleoni, Florence