Collaborative Research: Arctic Observing Network For Observing Transformation of the Greenland Ice Sheet Firn Layer

该奖项的全部或部分资金来自《2021年美国救援计划法案》(公法117-2)。由于北极变暖的速度比全球平均速度快两到三倍，格陵兰冰盖表面融化的持续时间和强度一般都在增加。大约90%的冰盖被压实的积雪覆盖，这些积雪正在慢慢转变为冰川冰。这种古老而致密的积雪被称为积雪，形成了一层数十米厚的多孔层。从降雪层表面产生的大部分融水渗入到降雪层下面开放的孔隙空间，然后重新冻结。然而，当这个多孔层吸收更多的熔体时，它会变得更温暖、更致密，并被冰层填满，这降低了它吸收额外熔体的能力。因此，格陵兰冰层目前正在经历的热和结构变化对冰盖保持未来融化的能力具有重要影响。这个项目是通过安装在积雪层内的仪器网络和冰芯对积雪进行采样来直接观察积雪的演化。该项目收集的观测数据提供了开发和测试用于大规模调查格陵兰冰盖变化的模型和遥感工具所需的降雪条件的实地记录。未来降雪层的变化将决定冰盖上局部保留了多少表面融化和流失了多少，从而影响到冰盖和周围地区的水文条件、海洋盐度和海平面上升。研究人员将沿着格陵兰冰盖的一条横断面安装和维护一个观测网络，直接测量降雪属性的状态和变化。对从地表到25米深的降雪岩芯和仪器的重复采样将产生多个科学界所需的观测数据集：降雪温度、密度和冰含量、致密率、地表边界过程(辐射、积雪、温度)和冰速。该网络将在这个为期五年的北极观测网络项目中产生4-5个全年记录。该项目将为过程级别的调查、测试降雪过程的气候模型模拟以及解释基于卫星的地表海拔变化测量提供全面的数据集。该项目将吸引和支持R2机构中具有实地研究经验和现实世界课堂学习的相对大量的本科生和研究生。外展活动将针对在冰冻圈科学中代表性较低的三个群体：1)格陵兰当地和土著居民；2)美国印第安人本科生；3)经济困难的学童。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。

This award is funded in whole or in part under the American Rescue Plan Act of 2021 (Public Law 117-2)As the Arctic warms two-to-three times faster than the global average, the duration and intensity of melting is generally increasing on the surface of the Greenland ice sheet. About 90% of ice sheet is covered by compacted snow that is slowly transitioning into glacier ice. This aged and dense snow is called ‘firn’ and forms a porous layer that is many tens of meters thick. Much of the meltwater generated from the surface of the firn layer infiltrates into the underlying open pore space of the firn and refreezes. However, as this porous layer absorbs more melt it becomes warmer, denser, and filled with ice layers, which reduces its ability to absorb additional melt. Therefore, the thermal and structural transformation that Greenland's firn layer is presently undergoing has important implications for the ice sheet's capacity to retain future melt. This project is directly observing firn evolution with a network of instruments installed within the firn layer and with ice cores sampling the firn. The observational data collected by this project provides on-the-ground documentation of firn conditions needed to develop and test models and remote sensing tools for large-scale investigations of changes to the Greenland ice sheet. Future transformation of the firn layer will govern how much surface melt is retained locally on the ice sheet and how much runs off, thereby impacting hydrologic conditions of the ice sheet and surrounding regions, ocean salinity, and sea level rise.The researchers will install and maintain an observation network along a transect of the Greenland ice sheet to directly measure the state and transformation of firn properties. Repeat sampling of firn cores and instrumentation extending from the surface to 25 meters depth will yield the observational datasets needed by multiple scientific communities: firn temperature, density and ice content, densification rate, surface boundary processes (radiation, snow accumulation, temperature), and ice velocity. The network will yield 4-5 full-year records in this five-year Arctic Observing Network project. The project will provide comprehensive datasets for process-level investigations, testing climate model simulations of firn processes, and interpreting satellite-based measurement of surface elevation change. The project will engage and support a relatively large number of undergraduate and graduate students at R2 institutions with field research experiences and real-world classroom learning. Outreach activities will target three groups poorly represented in cryospheric science: 1) local and Indigenous residents of Greenland; 2) American Indian undergraduate students; and 3) economically disadvantaged school children.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.