This project constructs POLENET a network of GPS and seismic stations in West Antarctica to understand how the mass of the West Antarctic ice sheet (WAIS) changes with time. The information is ultimately used to predict sea level rise accompanying global warming and interpret climate change records. The GPS (global positioning system) stations measure vertical and horizontal movements of bedrock, while the seismic stations characterize physical properties of the ice/rock interface, lithosphere, and mantle. Combined with satellite data, this project offers a more complete picture of the ice sheet's current state, its likely change in the near future, and its overall size during the last glacial maximum. This data will also be used to infer sub-ice sheet geology and the terrestrial heat flux, critical inputs to models of glacier movement. As well, this project improves tomographic models of the earth's deep interior and core through its location in the Earth's poorly instrumented southern hemisphere.
Broader impacts of this project are varied. The work is relevant to society for improving our understanding of the impacts of global warming on sea level rise. It also supports education at the postdoctoral, graduate, and undergraduate levels, and outreach to groups underrepresented in the sciences. As an International Polar Year contribution, this project establishes a legacy of infrastructure for polar measurements. It also involves an international collaboration of twenty four countries. For more information see IPY Project #185 at IPY.org. NSF is supporting a complementary Arctic POLENET array being constructed in Greenland under NSF Award #0632320.
Abstract
This award supports a seismological study of the Gamburtsev Subglacial Mountains (GSM), a Texas-sized mountain range buried beneath the ice sheets of East Antarctica. The project will perform a passive seismic experiment deploying twenty-three seismic stations over the GSM to characterize the structure of the crust and upper mantle, and determine the processes driving uplift. The outcomes will also offer constraints on the terrestrial heat flux, a key variable in modeling ice sheet formation and behavior. Virtually unexplored, the GSM represents the largest unstudied area of crustal uplift on earth. As well, the region is the starting point for growth of the Antarctic ice sheets.
Because of these outstanding questions, the GSM has been identified by the international Antarctic science community as a research focus for the International Polar Year (2007-2009). In addition to this seismic experiment, NSF is also supporting an aerogeophysical survey of the GSM under award number 0632292. Major international partners in the project include Germany, China, Australia, and the United Kingdom. For more information see IPY Project #67 at IPY.org. In terms of broader impacts, this project also supports postdoctoral and graduate student research, and various forms of outreach.
This grant funded the installation of a network of seismograph stations and GPS receivers (POLENET/ANET) in West Antarctica. Washington University was involved with the seismograph installation and data analysis so this report focuses on these aspects of the POLENET project. Installation of the seismographs began in late 2007 and continued until 2011 (figure 1). A line of temporary seismic stations were also installed across Marie Byrd Land and the West Antarctic Rift System from early 2010 to early 2012. The seismic stations operated successfully in the rugged Antarctic conditions and achieved 85-90% data return. Several important results from the project: We discovered an active volcanic system beneath nearly 1 mile of ice in Marie Byrd Land, by identifying the seismic signals from the magma system [Lough et al., 2013] (figure 2). Mapping of seismic anisotropy (the directional dependence of seismic velocity) shows that the earth's mantle is extensively deformed beneath West Antarctica. The fast direction of anisotropy is parallel with the direction of stretching along the West Antarctic Rift System (Accardo et al, 2014). Mapping of crustal thickness throughout West Antarctica shows very thin crust (about 20 km) along parts of the West Antarctic Rift system, demonstrating the large degree of crustal extension (Chaput et al., 2014).
