Collaborative Research: Temporal Variations in Glacial and Subglacial Structures of Antarctica

Suny At Stony Brook, Stony Brook NY

Investigators

Abstract

Continental-scale ice sheets in the polar regions (i.e., Antarctica and Greenland) hold 99 percent of the fresh water on Earth. These ice sheets are prone to undergoing fast changes in a shifting climate and may contribute significantly to future sea level rise. The physical properties of the ice sheets contain important information that can aid understanding of ice sheet dynamics (why they move) and provide hints on how ice sheets themselves respond to the changing climate. Therefore, making comprehensive observations of the time-dependent physical properties of the ice sheets is critical to better predict how much and how fast these systems will contribute to sea level rise. By leveraging existing seismic data, this project will aid the understanding of how seismic properties within and beneath the ice sheets change over time. Seasonal changes in subglacial conditions, revealed by seismic energy from remote earthquakes and ambient noise, are directly related to the evolution of subglacial hydrological systems. Targets of the research include near-surface seismic properties, which will reveal possible changes within and local conditions of the firn, a shallow layer used to understand long-term trends and improve regional climate models. Results from Antarctica will be compared to those from the Greenland ice sheet to isolate true seasonal signatures in the response of ice sheets in northern and southern polar regions to seasonal atmospheric and climate forcing. Further, sub-glacial solid Earth properties help constrain the geology of the ice-covered continent. In addition to the research efforts, the project will support a female graduate student, a female scientist and an early career (non-tenured) faculty, with additional educational efforts catering to the needs of K-12 and undergraduate students. Seismic properties within and beneath Antarctic ice sheets reflect physical changes in firn and subglacial hydrological systems and thus contain information on how the ice sheets are changing now and may change in the future. Seismic ambient noise and teleseismic wave measurements display geographical and temporal variations of near-surface and deeper properties, described to date in polar regions such as Greenland. A systematic survey of temporal variations has not yet been performed across all of Antarctica. Preliminary findings suggest seasonal variations in seismic observations (e.g., up to ±20% annual shear velocity change), and initial comparisons between sensors and hemispheres suggest true physical changes within the ice sheet and at its base are being detected. This project will perform a comprehensive analysis of seismic data collected by more than 600 stations in Antarctica over the past two decades, focusing on seasonal and long-term temporal changes recorded in various data products from both body and surface waves. This project will investigate: 1) Body-wave receiver function waveform analysis and their vertical-to-horizontal initial amplitude ratio, a novel approach to investigate shear velocity in the top few meters to several km; 2) Surface wave analysis (horizontal-to-vertical ratios method using both ambient noise and teleseismic earthquakes); and 3) Ambient noise coda, which helps characterize subglacial hydrological systems. Notably, the first two measurements (horizontal-to-vertical ratios and radio-frequency amplitudes) will be incorporated in a novel method to constrain temporal changes in the top tens of meters of the ice sheet down to tens of kilometers depth, resolving the ice sheet base and crust below. 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.