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

第一部分，非技术摘要40多年前，人们首次表示担心，由于气候变暖，南极西部冰盖（WAIS）可能容易将其冰作为巨大的冰山释放到南大洋，从而提高全球海平面。为了最好地评估这种威胁，科学家需要知道这些事件是否发生在地质学上最近的过去，在过去的冰川-间冰期循环的温暖时期。2019年，在WAIS最脆弱的区域附近进行的海洋钻探产生了海底地质记录，显示了冰山在阿蒙森海深水中落下大量沙子和鹅卵石的时间，称为冰筏碎屑（IRD）。 与从冰盖下的基岩被侵蚀的IRD一起，有丰富的硅藻（藻类浮游生物）的微化石，这表明开阔海洋的生物生产力很高。新的沉积物岩心提供了一个完整的，不间断的记录，在过去300万年发生的冰盖范围的剧烈波动的时间。 因此，它们提供了一种手段，可以明确地回答过去是否发生过冰盖崩塌的问题，并为未来的可能性提供线索。该项目将调查沉积物间隔，其中IRD与高硅藻生产的证据相吻合，以测试这两个标准是否表明冰盖快速崩溃。对IRD卵石的地球化学分析将有助于追踪冰山的来源，以找到可能的陆地位置。通过分析深海沉积物中高硅藻和IRD积累的条件，可以避免当地海岸的影响，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，可以转化为冰盖下降的速度。这些结果将为设计、约束和测试下一套计算机模型提供关键数据，这些模型可以确定未来冰盖在变暖的世界中崩溃的可能性和时间。该项目将包括对来自不同背景的本科生和研究生进行培训，并将向公众介绍南极科学，并通过几种不同的外联工作参与其中。第2部分，技术摘要来自南极洲阿蒙森海的新岩芯（IODP Expedition 379）包含了过去500万年来海洋学变化和冰山漂流碎片（IRD）的连续记录。本研究的目的是确定这些大陆边缘，深海沉积物的西南极冰盖（WAIS）的退缩/崩溃的签名，通过定量分析，详细，硅藻和IRD记录跨冰川间冰期岩石地层过渡，以建立晚上新世和更新世WAIS崩溃事件的时间和频率。调查人员将利用硅藻组合的高分辨率微体古生物学以及IRD沉积事件的微地层学分析，确保对U1532和U1533站点岩心的选定间冰期间隔的海洋古环境条件进行年龄限制和诊断观察，而冰山筏状碎屑的岩相学、地质年代学和热年代学将提供冰山来源和途径的证据。沉积古温度将通过一个新的古温度代理的基础上，在占主导地位的南大洋硅藻Fragilariopsis kerguelensis形态变化的定量评估进行评估。他们的研究结果将有助于新的冰盖模型的参数化，以重建和预测南极西部冰盖的行为。该项目将直接促进一所只招收本科生的学院和一所公立大学的本科生教育，该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，拟议的工作将允许本科生通过动手研究，致力于社会相关的研究合作团队内开发各种技能。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。来自南极洲西部深海记录的发现将由学生和研究人员在国家和国际会议以及一系列公共科学推广活动中进行交流。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。

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.