Collaborative Research: Testing the Linchpin of WAIS Collapse with Diatoms and IRD in Pleistocene and Late Pliocene Strata of the Resolution Drift, Amundsen Sea, Antarctica

合作研究：用硅藻和 IRD 测试南极洲阿蒙森海分辨率漂移的更新世和上新世晚期地层中 WAIS 塌陷的关键

• 批准号: 1939139
• 负责人: Reed Scherer
• 金额: $ 27.08万
• 依托单位: Northern Illinois University
• 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: 2020-06-01 至 2024-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1939139&HistoricalAwards=false
• 关键词: Collaborative; Research; Testing; Linchpin; WAIS

Part I, Non-technical Abstract Concerns that the West Antarctic Ice Sheet (WAIS) might be susceptible to releasing its ice as giant icebergs into the Southern Ocean due to a warming climate, raising global sea level, were first expressed more than 40 years ago. To best-assess this threat, scientists need to know whether such events occurred in the geologically recent past, during warm intervals of past glacial-interglacial cycles. Ocean drilling near the most vulnerable sector of the WAIS, in 2019, yielded seafloor geologic records demonstrating times when icebergs dropped large volumes of sands and pebbles, called ice-rafted detritus (IRD) in deep water of the Amundsen Sea. Occurring together with IRD that was eroded from bedrock beneath the ice sheets, there are abundant microfossils of diatoms (algal plankton), which indicate high biological productivity in the open ocean. The new sediment cores provide a complete, uninterrupted record of a time of dramatic fluctuations of ice sheet extent that occurred over the last 3 million years. Therefore, they provide the means to obtain clear answers to the question whether ice sheet collapse occurred in the past and offering clues to its potential future. This project will investigate sediment intervals where IRD coincides with evidence of high diatom production, to test whether these two criteria indicate rapid ice sheet collapse. Geochemical analysis of IRD pebbles will help trace the source of the icebergs to likely on-land sites. By analyzing conditions of high diatom and IRD accumulation in deep ocean sediment, where local coastal influences can be avoided, we will assess oceanographic and climatic conditions associated with past ice sheet collapse events. Diatoms provide powerful evidence of temperature and ocean productivity changes in the past, that, when linked to time, can translate into rates of ice sheet drawdown. These results will provide critical data for designing, constraining and testing the next suite computer models that can determine the likelihood and timing of future ice sheet collapse in a warming world. The project will include training of undergraduate and graduate students from diverse backgrounds, and the public will be introduced to Antarctic science and engaged through several different outreach efforts.Part 2, Technical AbstractNew drillcores from the Amundsen Sea, Antarctica (IODP Expedition 379) contain a continuous record of oceanographic changes and iceberg rafted debris (IRD) spanning the last 5 million years. This study aims to identify the signature of retreat/collapse of the West Antarctic Ice Sheet (WAIS) in these continental margin, deep-sea sediments by quantitatively analyzing, in detail, diatom and IRD records across glacial-interglacial lithostratigraphic transitions to establish the timing and frequency of Late Pliocene and Pleistocene WAIS collapse events. The investigators will secure age constraints and diagnostic observations of marine paleoenvironmental conditions for selected interglacial intervals of cores from sites U1532 and U1533, using high resolution micropaleontology of diatom assemblages coupled with microstratigraphic analysis of IRD depositional events, while petrography, geochronology and thermochronology of iceberg rafted clasts will provide evidence of iceberg sources and pathways. Depositional paleotemperatures will be assessed via a new paleotemperature proxy based on quantitative assessment of morphologic changes in the dominant Southern Ocean diatom Fragilariopsis kerguelensis. Their results will contribute to parameterization of new ice sheet models that seek to reconstruct and forecast West Antarctic Ice Sheet behavior. This project will directly contribute to undergraduate education at an undergraduate-only college and at a public university that serves a demographic typified by first generation university students and underrepresented groups. Spanning geology, geochemistry, sedimentology, paleontology and paleoceanography, the proposed work will allow undergraduate students to develop diverse skills through hands-on research within a collaborative team that is dedicated to societally relevant research. The two graduate students will conduct original research and work alongside/mentor undergraduates, making for a well-rounded research experience that prepares them for success in future academic or employment sectors. The discoveries that come from this deep-sea record from West Antarctica will be communicated by students and investigators at national and international conferences and an array of public science outreach events.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.

由于气候变暖，全球海平面上升，人们对南极西部冰盖（WAIS）可能会以巨大冰山的形式向南大洋释放冰的担忧在40多年前首次提出。为了最好地评估这种威胁，科学家们需要知道这些事件是否发生在地质上最近的过去，在过去冰期-间冰期旋回的温暖间隔期间。2019年，在WAIS最脆弱的区域附近进行海洋钻探，获得了海底地质记录，显示了冰山在阿蒙森海深水中落下大量沙子和鹅卵石（称为冰筏碎屑（IRD））的时间。与冰盖下基岩侵蚀形成的IRD一起发育的硅藻（浮游藻类）微化石丰富，表明开阔海域生物生产力较高。新的沉积物岩心提供了一个完整的、不间断的记录，记录了在过去300万年里发生的冰盖范围剧烈波动的时期。因此，它们提供了一种方法，可以明确回答过去是否发生过冰盖崩塌的问题，并为其潜在的未来提供线索。该项目将调查IRD与高硅藻产量证据相吻合的沉积物间隔，以测试这两个标准是否表明冰盖迅速崩塌。对IRD鹅卵石的地球化学分析将有助于追踪冰山可能在陆地上的来源。通过分析深海沉积物中高硅藻和IRD积累的条件，我们将评估与过去冰盖崩塌事件相关的海洋和气候条件。硅藻提供了过去温度和海洋生产力变化的有力证据，当与时间联系起来时，可以转化为冰盖减少的速度。这些结果将为设计、限制和测试下一套计算机模型提供关键数据，这些模型可以确定在变暖的世界中未来冰盖崩塌的可能性和时间。该项目将包括对来自不同背景的本科生和研究生的培训，并通过几项不同的外展工作向公众介绍南极科学并参与其中。来自南极洲阿蒙森海的新钻探岩芯（IODP 379考察队）包含了过去500万年海洋变化和冰山漂流碎片（IRD）的连续记录。本研究旨在通过定量分析南极西部冰盖（WAIS）在冰川-间冰期岩石地层转换过程中的硅藻和IRD记录，确定晚上新世和更新世WAIS崩塌事件的时间和频率，从而识别南极西部冰盖（WAIS）在大陆边缘深海沉积物中的退缩/崩塌特征。研究人员将利用硅藻组合的高分辨率微古生物学，结合IRD沉积事件的微地层分析，对U1532和U1533地点选定的间冰期岩心进行年龄限制和海洋古环境条件的诊断观察，而冰山漂流碎屑的岩石学、地质年代学和热年代学将提供冰山来源和路径的证据。在定量评价南大洋优势硅藻Fragilariopsis kerguelensis形态变化的基础上，采用一种新的古地温代用物来评价沉积古地温。他们的结果将有助于新的冰盖模型的参数化，这些模型旨在重建和预测南极西部冰盖的行为。该项目将直接为本科学院和公立大学的本科教育做出贡献，这些大学为第一代大学生和代表性不足的群体提供服务。横跨地质学、地球化学、沉积学、古生物学和古海洋学，这项工作将允许本科生通过在一个致力于社会相关研究的合作团队中进行实践研究来发展各种技能。这两名研究生将进行原创性研究，并与本科生一起工作/指导本科生，为他们在未来的学术或就业领域取得成功做好准备。来自南极西部深海记录的发现将由学生和调查人员在国内和国际会议上以及一系列公共科学推广活动上进行交流。该奖项反映了美国国家科学基金会的法定使命，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。

项目成果

Latitudinal Variance in the Drivers and Pacing of Warmth During Mid‐Pleistocene MIS 31 in the Antarctic Zone of the Southern Ocean

南大洋南极区中更新世 MIS 31 期间温暖驱动因素和节奏的纬度变化

• DOI: 10.1029/2021pa004394
• 发表时间: 2022
• 期刊: Paleoceanography and Paleoclimatology
• 影响因子: 3.5
• 作者: Warnock, Jonathan P.;Reilly, Brendan T.;Raymo, Maureen E.;Weber, Michael E.;Peck, Victoria;Williams, Trevor;Armbrecht, Linda;Bailey, Ian;Brachfeld, Stefanie;Du, Zhiheng
• 通讯作者: Du, Zhiheng