West Antarctic Ice-sheet Change and Paleoceanography in the Amundsen Sea Across the Pliocene Climatic Optimum

南极西部冰原是最易受变暖影响的极地冰块，已经是全球平均海平面上升的主要原因。鉴于持续变暖，它的命运是一个非常不确定的话题。由于极地地区的冰块减少，海平面加速上升是一个主要问题，因为它会导致沿海洪水增加，影响数百万人。这个项目将揭示埋在南极洲阿蒙森海海底下的一个独特的地质档案，它将揭示南极西部冰盖在过去温暖气候下的表现。这些数据和见解可用于沿海政策制定中使用的冰盖和海洋模型。该项目还将支持培养具有竞争力的美国STEM劳动力。地质学入门课程的在线课堂练习将为合格的学生进入本科研究项目提供一个门户，该项目将通过资助当前女博士生的教育来提高女性对科学的参与。该项目的目标是在上新世早期沉积记录中，南极西部冰盖在几个冰期-间冰期旋回的长期变化，这些沉积记录是由国际海洋发现计划（IODP）第379队在阿蒙森海钻探的。数据收集包括：1)阿蒙森海和南极半岛地区冰碛碎屑和陆架碎屑岩的砂源及其来源；2)根据粒度记录和电流强度和相互作用的重建计算沉积结构和可分选泥沙；3)与阿蒙森海陆架的现有数据相比，大陆隆起沉积物的大部分物源与南极底水形成途径的下坡流调查相比较。结果在反射光谱和比色法（RSC）和x射线荧光扫描仪（XRF）数据的旋回地层框架内进行分析，以深入了解高纬度过程的轨道强迫。根据深海稳定同位素和海表温度记录，上新世早期的气候适宜期（PCO）为4.5 ~ 4.1 Ma，是一个主要的暖期。这一时期也与全球平均海平面上升20米相吻合，这需要南极洲的冰块损失。以下假设将得到验证：1)在PCO ~4.5 Ma开始时，由于次冰架融化和冰山崩解的增加，西南极冰盖从大陆架撤退；2)在~4.5 Ma之后，由于冰架在冰川终止期间暴露，密集的大陆架水通过斜坡通道瀑布状下降。该项目将首次揭示在目前的“冰窖”时期（3.3 Ma）开始之前，南极西部冰盖是如何在更温暖的气候状态下运作的。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。

The West Antarctic Ice Sheet is the most vulnerable polar ice mass to warming and already a major contributor to global mean sea level rise. Its fate in the light of prolonged warming is a topic of major uncertainty. Accelerated sea level rise from ice mass loss in the polar regions is a major concern as a cause of increased coastal flooding affecting millions of people. This project will disclose a unique geological archive buried beneath the seafloor off the Amundsen Sea, Antarctica, which will reveal how the West Antarctic Ice Sheet behaved in a warmer climate in the past. The data and insights can be used to inform ice-sheet and ocean modeling used in coastal policy development. The project will also support the development of a competitive U.S. STEM workforce. Online class exercises for introductory geology classes will provide a gateway for qualified students into undergraduate research programs and this project will enhance the participation of women in science by funding the education of current female Ph.D. students.The project targets the long-term variability of the West Antarctic Ice Sheet over several glacial-interglacial cycles in the early Pliocene sedimentary record drilled by the International Ocean Discovery Program (IODP) Expedition 379 in the Amundsen Sea. Data collection includes 1) the sand provenance of ice-rafted debris and shelf diamictites and its sources within the Amundsen Sea and Antarctic Peninsula region; 2) sedimentary structures and sortable silt calculations from particle size records and reconstructions of current intensities and interactions; and 3) the bulk provenance of continental rise sediments compared to existing data from the Amundsen Sea shelf with investigations into downslope currents as pathways for Antarctic Bottom Water formation. The results are analyzed within a cyclostratigraphic framework of reflectance spectroscopy and colorimetry (RSC) and X-ray fluorescence scanner (XRF) data to gain insight into orbital forcing of the high-latitude processes. The early Pliocene Climatic Optimum (PCO) ~4.5-4.1 Ma spans a major warm period recognized in deep-sea stable isotope and sea-surface temperature records. This period also coincides with a global mean sea level highstand of 20 m requiring contributions in ice mass loss from Antarctica. The following hypotheses will be tested: 1) that the West Antarctic Ice Sheet retreated from the continental shelf break through an increase in sub iceshelf melt and iceberg calving at the onset of the PCO ~4.5 Ma, and 2) that dense shelf water cascaded down through slope channels after ~4.5 Ma as the continental shelf became exposed during glacial terminations. The project will reveal for the first time how the West Antarctic Ice Sheet operated in a warmer climate state prior to the onset of the current “icehouse” period ~3.3 Ma.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.