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，北美的劳伦泰德冰原的生长和收缩引起了气候和海平面的巨大变化，但在这段时间内，人们对冰原的详细历史知之甚少。这个项目将利用从北美漂流来的冰山融化的海底沙层中的化学标记物来确定冰盖在过去的时间里有多大。这种方法为了解劳伦泰德冰盖过去的变化提供了一种新的方法，并测试了气候变化和冰盖如何相互影响的想法。研究结果应该有助于预测由于全球变暖和极地冰盖融化导致的未来海平面上升。该项目还将以多种方式教育和参与气候科学的广泛人群。有关该研究的视频将通过BoSTEM组织发送到波士顿公立学校，以帮助该地区的学生了解科学职业。研究人员将通过弗雷明汉州立大学的麦考利夫综合科学学习中心参加活动，向初高中学生和教师讲授气候变化。大学生们将在暑假期间通过波士顿学院的“社会科学与科学基金会本科生综合研究经验”项目帮助这项研究，该项目试图找到来自代表性不足的少数群体的学生，或者是家庭中第一个上大学的学生，他们在学校没有研究机会。最后，该项目将支持一名已经在波士顿学院攻读博士学位的女学生和一名在佛蒙特大学攻读硕士学位的学生。在过去300万年的冰期周期中，北美的劳伦泰德冰盖是气候和海平面变化的最大驱动因素之一，但由于常规地质记录的限制，它在这段时间内的历史笼罩在不确定之中。这个项目将采用一种新的方法，测量从漂流的北美冰山融化的海洋沉积物岩心中提取的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覆盖的历史，因为化学物质在暴露于大气中的陆地表面积累，但当表面被冰掩埋时，放射性物质就会衰变。将对四个沉积物岩心进行分析，以重建劳伦泰德冰盖的长期演变，对加拿大东部收集的沙子样本进行分析，将显示它们的化学成分如何记录冰盖在最近冰期周期中的变化。再加上过去五年在格陵兰岛和南极洲进行的类似重建，这些记录将提供一个全面的画面，说明这三个冰盖在过去是如何变化的，以及对全球海平面的影响。这些结果将为检验古冰盖变化的理论和模型提供急需的约束条件，有助于改进对当今地球冰盖的长期预测。该项目将以多种方式提高气候科学的识字率和多样性。有关这项研究的“科学叮咬”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。通过弗雷明汉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，将有助于对初高中教师和学生进行气候变化教育。该项目将资助波士顿学院的一名在读女博士和佛蒙特大学的一名在读硕士。夏季本科生研究助理将通过波士顿学院的社会综合科学NSF REU招聘，该机构旨在吸引来自研究机会有限的学校的少数族裔和第一代大学生。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 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.