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

点击翻译按钮获取中文摘要

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.