Collaborative Research: 3 Myr of Laurentide Ice Sheet History Inferred from Cosmogenic Nuclides in Ice-Rafted Debris

在过去300万年的冰期周期中，北美的劳伦蒂德冰盖引起了气候和海平面的巨大变化，但人们对这段时间内冰盖的详细历史知之甚少。该项目将使用从北美漂流来的冰山融化的海底沙层中的化学标记，来确定随着时间的推移冰盖有多大。这种方法提供了一种新的方法来了解劳伦蒂德冰盖过去的变化，并测试气候变化和冰盖如何相互影响的想法。这一结果应该有助于预测，由于全球变暖和极地冰盖融化，海平面在很长一段时间内都会上升。该项目还将以几种方式教育和参与气候科学方面的广泛人员。有关这项研究的视频将通过BoSTEM组织发送到波士顿公立学校，帮助该地区的学生了解科学职业。研究人员将通过弗雷明翰州立大学麦考利夫综合科学学习中心参与活动，向初中生和教师传授气候变化知识。大学生将在暑假期间通过波士顿学院面向本科生的NSF综合科学研究体验项目帮助进行研究，该项目试图寻找来自代表性不足的少数群体的学生，或者是他们家族中第一个上大学的学生，以及他们的学校没有研究可能性的学生。最后，该项目将支持一名已在波士顿学院攻读博士学位的女学生和一名在佛蒙特州大学攻读硕士学位的学生。在过去三百万年的冰期周期中，北美的劳伦蒂德冰盖是气候和海平面的最大驱动因素之一，但它在这段时间内的历史在很大程度上由于传统地质记录的限制而笼罩在不确定性之中。该项目将采用一种新的方法，测量漂浮的北美冰山融化的海洋沉积物岩芯中石英砂层中稀有化学物质的浓度。沙子的化学成分反映了北美冰盖的历史，因为这些化学物质在暴露在大气中的陆地表面积累，但当地面被冰掩埋时，这些化学物质就会放射性衰变。将对四个沉积物岩芯进行分析，以重建Laurentide冰盖的长期演化，对加拿大东部收集的沙子样本的分析将显示它们的化学物质如何记录最近一个冰期周期的冰盖变化。连同格陵兰和南极洲在过去五年中制作的类似重建图，这些记录将提供这三个冰盖在过去如何变化并对全球海平面做出贡献的全面图景。这些结果将为检验古冰盖变化的理论和模型提供亟需的约束，有助于改进对当今地球冰盖的长期未来预测。该项目将以多种方式提高气候科学的识字率和多样性。关于这项研究的“Science Bites”视频将通过BoSTEM分发给波士顿公立学校，以揭开科学职业的神秘面纱。通过弗雷明翰州立大学麦考利夫综合科学学习中心参与正在进行的努力，将有助于教育初中和高中教师和学生有关气候变化的知识。该项目将支持波士顿学院现有的一名女博士生和佛蒙特州大学的一名硕士研究生。暑期本科生研究助理将通过波士顿学院的社会综合科学研究联盟招聘，该联盟旨在从研究机会有限的学校吸引代表不足的少数族裔和第一代大学生。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

The Laurentide Ice Sheet over North America caused large changes in climate and sea level as it grew and shrank over ice age cycles during the past three million years, but little is known about the ice sheet’s detailed history throughout this interval. This project will determine how big the ice sheet was through time using chemical markers in layers of sand on the seafloor that melted out of icebergs drifting from North America. This method provides a new way to learn about past changes in the Laurentide Ice Sheet and test ideas for how climate change and ice sheets affect each other. The results should help with predictions of sea-level rise far into the future due to global warming and melting polar ice sheets. This project will also educate and involve a wide range of people in climate science in several ways. Videos about the research will be sent to Boston Public Schools through the BoSTEM organization to help students in the area learn about careers in science. The researchers will participate in activities through the McAuliffe Center for Integrated Science Learning at Framingham State University to teach middle and high school students and teachers about climate change. College students will help with the research during summers through the Integrated Science for Society NSF Research Experience for Undergraduates at Boston College, which tries to find students from underrepresented minority groups or who are the first in their family to go to college and that do not have research possibilities at their school. Lastly, the project will support a female Ph.D. student already at Boston College and an M.S. student at the University of Vermont. The Laurentide Ice Sheet over North America was one of the largest drivers of climate and sea level over the ice age cycles of the past three million years, but its history over this interval is shrouded in uncertainty largely due to limitations of conventional geologic records. This project will take a new approach, measuring the concentrations of rare chemicals in quartz sand layers from ocean sediment cores that melted out of drifting North American icebergs. The chemistry of the sand reflects the history of North American ice sheet cover because the chemicals accumulate in land surfaces exposed to the atmosphere but radioactively decay away when the surfaces are buried by ice. Four sediment cores will be analyzed to reconstruct long-term Laurentide Ice Sheet evolution, and analyses of sand samples collected across eastern Canada will show how their chemistry records ice sheet variations over the most recent ice age cycle. Together with similar reconstructions produced over the past five years from Greenland and Antarctica, these records will provide a comprehensive picture of how these three ice sheets varied in the past and contributed to global sea level. The results will offer much-needed constraints to test theories and models of paleo-ice sheet change, useful for improving long-term future projections of ice sheets on Earth today. This project will increase literacy and diversity in climate science in multiple ways. “Science Bites” videos about the research will be distributed to Boston Public Schools through BoSTEM to demystify careers in science. Participation in ongoing efforts through the McAuliffe Center for Integrated Science Learning at Framingham State University will help educate middle and high school teachers and students on climate change. This project will support an existing female Ph.D. student at Boston College and an M.S. student at the University of Vermont. Summer undergraduate research assistants will be recruited through the Integrated Science for Society NSF REU at Boston College, which seeks to attract underrepresented minority and first-generation college students from schools with limited research opportunities.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.