Greenland-wide Assessment of Proglacial Melange Variability and Implications for Glacier Retreat

在格陵兰冰盖的边缘有200多个出水口冰川，它们将厚厚的冰层从内部排入周围的海洋。随着这些冰川的退缩和加速，它们以更快的速度从冰盖上带走了物质。因此，为了量化和预测格陵兰岛在全球海平面上升中的作用，了解驱动冰川前进和后退模式的过程是很重要的。这个项目使用卫星数据来研究冰凌（海冰和冰山的混合物）对格陵兰冰川退缩的时间和规模的影响。由于对msamdange的分布还不太了解，这个项目将首先测量msamdange的覆盖范围，显示它在冰盖周围形成和分解的时间，并绘制地图和时间序列，供其他科学家在他们的研究中使用。然后，项目团队将这些数据产品与冰川锋面随时间变化的测量结果进行比较，以调查冰川前的msamdange是否可以限制退缩，确定msamdange最重要的地方，并量化msamdange覆盖范围是否随时间变化。该项目由一位获得首个美国国家科学基金会奖的早期职业研究者领导，将促进女性在STEM领域的充分参与，并在解决重要科学问题之外实现几个更广泛的影响。该团队将通过旨在促进多样性的渠道招募夏季本科生研究人员，通过参与公共教育活动中与冰川相关的互动活动，以及在小学到大学的课堂上志愿担任客座演讲，来增加代表性和公众科学素养。流入周围海洋的出口冰川是格陵兰冰盖质量平衡的重要组成部分，出口冰川的长度和速度的变化会影响冰从冰盖上移除的速度。在冰山从正在崩解的冰川中分离出来的地区，海冰可能会与冰山混合，形成一种重新冻结的、半刚性的混合物，这种混合物被称为msamulange。msamlange会在峡湾积聚，并聚集在冰川崩解前沿附近的地区，这可能会限制冰川退缩的程度和持续时间。尽管它可能对冰川出口退缩和速度的季节性变化模式产生影响，但在整个冰原范围内，既没有测量过它的总面积，也没有测量过它覆盖的时间和持续时间。该项目将对格陵兰岛的msamange条件进行第一次强有力的大规模评估，以量化msamange在冰川出口行为中的作用及其对冰川和冰盖质量损失的净影响。这项研究将大量利用Sentinel-1卫星任务的雷达数据，该卫星任务每6到12天对格陵兰岛海岸线的大部分地区进行成像，并调整现有的冰川速度跟踪方法，以在冰川出口峡湾的固结或刚性冰川区域发挥作用。在此过程中，该项目还将开发和分发重要的新数据产品，这些产品可以绘制出固定的msamdange条件随时间变化的位置，并结合每周的地图来测量msamdange在格陵兰周围特定地点出现的频率。通过与现有数据集和工具的合作，项目团队将把msamange数据与冰川前沿变化的测量结果进行比较，包括前沿位置、冰厚、冰川形状以及冰山的大小和分布。这些分析将用于更好地了解当地的地理和环境条件与msamuange形成的关系，并最终帮助确定哪里的msamuange形成对冰川崩解最重要。这项工作的结果将包括超出科学价值的更广泛的影响。除了在开发和共享新数据集时采用开放科学原则外，该团队还将整合旨在增加少数群体在STEM中的代表性和参与度的活动和方法，并提高公众对科学和技术的极性素养和参与度。该项目的首席研究员是一位早期的职业女性，她领导了她的第一个nsf支持的研究，她将与现有的项目密切合作，这些项目旨在为代表性不足的人群提供服务，在招收学生参加暑期有偿研究经历时，这是对项目目标的补充。该团队还将在面向公众的社区教育活动中参与与冰川相关的演示，首席研究员将把项目结果和成果纳入计划在小学到大学课堂上进行的客座演讲。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。

Over two hundred outlet glaciers line the edges of the Greenland ice sheet, where they drain thick ice from the interior into the surrounding ocean. As these glaciers retreat and speed up, they remove mass from the ice sheet at a faster rate. Therefore, to quantify and predict Greenland’s role in global sea level rise, it is important to understand what processes drive patterns of glacier advance and retreat. This project uses satellite data to study the impact of ice mélange, or the mixture of sea ice and icebergs, on the timing and magnitude of glacier retreat in Greenland. Because the distribution of mélange is not well known, this project will first measure mélange coverage, show when it forms and breaks up around the ice sheet, and create maps and time series for other scientists to use in their research. The project team will then compare these data products to measurements of changing glacier fronts through time to investigate whether mélange in front of glaciers can limit retreat, identify where mélange is most important, and quantify if mélange coverage is changing over time. Led by an early career investigator on her first NSF award, this project will promote the full participation of women in STEM and accomplish several broader impacts beyond addressing important scientific questions. The team will increase representations and public science literacy by recruiting summer undergraduate researchers through channels aimed at promoting diversity, by participating in interactive glacier-related activities at public educational events, and by volunteering in guest speaking engagements at elementary through university-level classrooms. Outlet glaciers that flow out into the surrounding ocean are an important component of the Greenland ice sheet mass balance, and changes in outlet glacier length and speed can affect how rapidly ice is removed from the ice sheet through time. In areas where icebergs break off from calving glaciers, sea ice may intermix with icebergs and form a refrozen, semi-rigid mixture called mélange. Mélange can build up in the fjord and crowd the area near the glacier calving front, potentially limiting how much and for how long retreat can occur. Despite its likely impact on changing seasonal patterns of outlet glacier retreat and speed, neither the total area of mélange nor the timing and duration of its coverage have yet been measured on an ice sheet-wide scale. This project will conduct the first robust, large-scale assessment of mélange conditions in Greenland to quantify the role of mélange in outlet glacier behavior and its net impact on glacier and ice sheet mass loss. The study will heavily utilize radar data from the Sentinel-1 satellite mission, which images most areas of the Greenland coastline every 6 to 12 days, and adapt existing methods of glacier speed tracking to function over regions of consolidated, or rigid, mélange in outlet glacier fjords. In doing so, the project will also develop and distribute important new data products that map the location of rigid mélange conditions through time and combine the ~weekly maps to measure how often mélange is present at specific sites around Greenland. Through collaborative efforts with existing datasets and tools, the project team will compare the mélange data to measurements of glacier front changes, including front position, ice thickness, and glacier shape, as well as iceberg size and distribution. These analyses will be used to better understand how the local geographic and environmental conditions relate to mélange formation, and finally, help identify where mélange formation is most important for glacier calving. Outcomes of this work will include broader impacts that extend beyond the scientific merit. In addition to adopting open science principles in the development and sharing of new datasets, the team will also integrate activities and approaches aimed at increasing the representation and participation of minoritized groups in STEM, and at improving public polar literacy and engagement in science and technology. The project’s principal investigator is an early career woman leading her first NSF-supported study, and she will work closely with existing programs designed to serve underrepresented populations when recruiting students for paid summer research experiences that are complementary to the project’s goals. The team will also participate in glacier-related demonstrations in a public-facing, community educational event, and the lead investigator will incorporate project results and outcomes into guest speaking engagements planned for elementary through university-level classrooms.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.