A New Instrument and Measurement Approach to Cryo-Seismogeodesy: Monitoring Antarctic Ice Shelf Stability Using Ice Penetrators

第一部分：非技术性南极大陆被一层巨大的冰盖住。冰盖通过降雪获得质量，通过高耸的冰山融化和崩解而失去质量。损失主要发生在冰架上。这就是冰盖与海洋的交汇之处。南极陆基冰盖的稳定性取决于海洋冰架的稳定性，因为冰架起到了支撑物的作用，限制和调节了可以流入海洋的冰量。正如目前观察到的那样，当冰架变薄和变弱时，它们可能会解体，从而导致陆基冰加速排放到海洋中。一旦冰到达海洋，它就会加速海平面上升。因此，地球的气候和南极冰的状态通过冰架的稳定性紧密联系在一起。因此，了解南极冰架如何应对大气和海洋状况的持续变化至关重要。不幸的是，南极环境的条件是极端的。部署能够在这些条件下生存并测量冰架对大气赋予的力量的冰上反应的科学仪器，是一项后勤和工程挑战。因此，冰架的测量结果是稀少的。这些挑战可以通过开发一种坚固的仪器来应对，这种仪器可以将所需的科学传感器打包成一个可以空投到许多冰架上偏远位置的冰穿透器。该项目将把科学家用来研究地震和火山物理的最先进的传感器融合成一个单一的仪器，它将获得与冰架物理有关的测量结果。为了证明这种方法的价值，两台这样的仪器将从直升机上投放到麦克默多美军基地附近的罗斯冰架上，在那里它们将收集大约一年的科学数据，并通过卫星链路实时传递数据。该项目将包括本科生和研究生的大量参与。第二部分：技术说明南极冰架是南极冰盖稳定的关键因素，现正显示出迅速减少的迹象。冰架融化、退缩和变薄导致地面冰向海洋的排放量增加，并伴随着海平面的上升。冰架的解体可能会导致南极冰盖最终崩溃。尽管冰架在气候变暖的情况下对南极冰盖未来的命运起着关键作用，但冰架缺乏现场地震和大地测量数据。虽然地震大地测量可以揭示冰架对当今海洋和大气压力的反应，但在南极冰架上获得连续、高质量的测量是具有挑战性的。为了解决这些科学问题和应对观测挑战，该项目将首次将低温地震学和冷冻学结合到一个单一的仪器--地震大地冰穿透仪(SGIP)中，该仪器可以被空投到冰架表面，以帮助增进对南极冰-海洋-大气动力学的了解。地震大地测量仪提供了一种有效地观察和量化冰架稳定性的手段。地震大地测量仪的现场测试将在麦克默多附近的罗斯冰架上进行，在那里，两个地震大地测量仪将在第一季被直升机投放，并允许在冬季继续运行。第三个参考仪器将被手动植入空投的地震大地冰穿透器中，用于地面实况测量。来自这些仪器的科学和工程数据将通过卫星链路近乎实时地传递。地震大地测量仪和参考设备将在第二季回收。这一奖励反映了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。

Part I: Nontechnical The Antarctic continent is covered by a massive sheet of ice. The ice sheet gains mass by snowfall and losses mass by melting and calving of towering icebergs. Losses occur primarily at the ice shelves. These are where the ice sheet meets the ocean. The stability of the Antarctic land-based ice sheet depends on the stability of the oceanic ice shelves, because the ice shelves act as a buttress, restraining and modulating the amount of ice that can flow into the ocean. When ice shelves thin and weaken, as is currently observed, they can disintegrate, which leads to accelerated discharge of land-based ice to the ocean. Once the ice reaches the ocean, it contributes to accelerating sea-level rise. Thus, the Earth’s climate and the state of Antarctic ice are intimately linked through the stability of the ice shelves. It is therefore critical to understand how the Antarctic ice shelves are responding to ongoing changes in atmospheric and ocean conditions. Unfortunately, the conditions of the Antarctic environment are extreme. Deploying scientific instruments that can survive those conditions and measure the on-ice response of the shelves to forces imparted by the atmosphere is a logistics and an engineering challenge. As a result, ice-shelf measurements are sparse. These challenges can be met by developing a robust instrument that packages the desired scientific sensors into an ice penetrator that can be air dropped into remote locations on many ice shelves. This project will fuse state-of-the-art sensors that scientists use to study the physics of earthquakes and volcanoes into a single instrument that will obtain measurements pertaining to ice shelf physics. As a test to demonstrate the value of this approach, two such instruments will be dropped from a helicopter onto the Ross Ice Shelf near the US base at McMurdo, where they will collect science data for about a year, relaying the data in real time via satellite link. The project will include significant participation from undergraduate and graduate students. Part II: Technical Description Antarctic ice shelves, a critical element in the stability of the Antarctic Ice Sheet, are showing signs of rapid decline. Ice-shelf melting, retreating, and thinning lead to increased discharge of grounded ice to the ocean, and to concomitant sea-level rise. Ice-shelf disintegration could drive the Antarctic Ice Sheet to eventual collapse. Despite their key role in the future fate of the Antarctic Ice Sheet under a warming climate, ice shelves are lacking in-situ seismic and geodetic measurements. Although seismogeodetic measurements can unveil the response of the ice shelves to present-day ocean and atmospheric forcings, obtaining continuous, high-quality measurements on the Antarctic ice shelves is challenging. To address these scientific problems and tackle the observational challenges, This project will combine cryoseismology and cryogeodesy for the first time into a single instrument, a seismogeodetic ice penetrator (SGIP), that can be air-dropped onto an ice-shelf surface to help advance understanding of Antarctic ice-ocean-atmosphere dynamics. The seismogeodetic ice penetrator provides a means to efficiently observe and quantify ice-shelf stability. The seismogeodetic ice penetrator field testing will occur on the Ross Ice Shelf near McMurdo where two seismogeodetic ice penetrator units will be helicopter dropped in the first season and allowed to continuously operate over winter. A third, reference instrument will be manually implanted along an air-dropped seismogeodetic ice penetrator for ground-truthing. Science and engineering data from these instruments will be relayed over a satellite link in near-real time. The seismogeodetic ice penetrator and reference equipment will be recovered in the second season.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.