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

点击翻译按钮获取中文摘要

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.