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

200多个出口冰川排列在格陵兰冰盖的边缘，在那里它们将厚厚的冰从内陆排入周围的海洋。随着这些冰川的消退和加速，它们会以更快的速度从冰盖上移走质量。因此，要量化和预测格陵兰在全球海平面上升中的作用，重要的是要了解是什么过程驱动了冰川进退的模式。该项目利用卫星数据研究海冰和冰山的混合体对格陵兰岛冰川消退的时间和规模的影响。由于混杂的分布尚不为人所知，该项目将首先测量混杂的覆盖率，显示其在冰盖周围形成和破裂的时间，并创建地图和时间序列，供其他科学家在研究中使用。然后，项目组将把这些数据产品与随时间变化的冰川前缘的测量结果进行比较，以调查冰川前面的混杂是否可以限制消退，确定混杂在哪里最重要，并量化混杂的覆盖范围是否随着时间的推移而变化。该项目由一位早期职业调查员领导，获得了她的第一个NSF奖，该项目将促进妇女充分参与STEM，并在解决重要的科学问题之外实现几个更广泛的影响。该小组将通过旨在促进多样性的渠道招募暑期本科生研究人员，通过参加公共教育活动中与冰川有关的互动活动，以及通过志愿参加小学到大学一级课堂的嘉宾演讲活动，来增加陈述和公共科学素养。流入周围海洋的出口冰川是格陵兰冰盖物质平衡的重要组成部分，出口冰川长度和速度的变化可以影响随着时间的推移冰从冰盖上移走的速度。在冰山从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混合物，称为混杂。混杂可能会在峡湾堆积，并挤满冰川崩解前沿附近的地区，这可能会限制退缩的程度和持续时间。尽管它可能会对冰川出口退缩和速度的季节模式变化产生影响，但无论是混杂冰川的总面积，还是其覆盖的时间和持续时间，都尚未在整个冰盖范围内进行测量。该项目将对格陵兰岛的混杂条件进行第一次强有力的大规模评估，以量化混杂条件在出口冰川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哨兵一号卫星任务的雷达数据，该任务每隔6至12天对格陵兰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，使其适用于出口冰川峡湾的固结或刚性混杂区域。在这样做的同时，该项目还将开发和分发重要的新数据产品，这些产品绘制出刚性混杂条件随时间变化的位置，并结合每周地图来衡量格陵兰周围特定地点出现混杂的频率。通过与现有数据集和工具的合作，项目组将把混杂数据与冰川锋面变化的测量结果进行比较，包括冰川锋面位置、冰层厚度、冰川形状以及冰山的大小和分布。这些分析将被用来更好地了解当地的地理和环境条件与混杂形成的关系，并最终帮助确定混杂形成对冰川崩解最重要的地方。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的数据集方面采用开放科学原则外，该小组还将整合旨在增加小规模群体在STEM中的代表性和参与度、提高公众极地识字能力和参与科学技术的活动和方法。该项目的首席研究员是一名早期职业女性，她领导着她的第一项由NSF资助的研究，她将与现有的项目密切合作，这些项目旨在为代表不足的人群服务，当招收学生进行有偿暑期研究体验时，这些项目与该项目的目标相辅相成。该团队还将参加面向公众的社区教育活动中与冰川相关的演示，首席调查员将把项目结果和结果纳入计划在小学到大学课堂上的嘉宾演讲活动中。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。

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.