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

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普遍在增加。大约90%的冰盖被压实的雪覆盖，这些雪正在慢慢转变为冰川冰。这种古老而致密的雪被称为“firn”，形成了几十米厚的多孔层。从冰层表面产生的大部分融水渗透到冰层下的开放孔隙空间并重新冻结。然而，随着这个多孔层吸收更多的融水，它变得更温暖、更致密，并充满了冰层，这降低了它吸收额外融水的能力。因此，格陵兰冰层目前正在经历的热和结构转变对冰盖保持未来融化的能力具有重要意义。该项目通过安装在冰芯层内的仪器网络和冰芯取样直接观察冰芯的演变。本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坚实条件的实地文件。冰冻层的未来转变将决定冰盖局部保留多少表面融水和流失多少融水，从而影响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个样带安装并维护一个观测网，以直接测量公司属性的状态和变化。从地表延伸至25米深度的冰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：冰芯温度、密度和冰含量、致密化率、表面边界过程（辐射、积雪、温度）和冰速度。在这个为期五年的北极观测网络项目中，该网络将产生4-5个全年记录。该项目将为过程级调查提供全面的数据集，测试气候模式模拟的过程，并解释基于卫星的地表高程变化测量。该项目将吸引并支持R2机构中相当多的本科生和研究生，让他们拥有实地研究经验和现实世界的课堂学习。外联活动将针对在冰冻圈科学中代表性不足的三个群体：1)格陵兰的当地居民和土著居民；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。

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.