| Summary: | Continuously recording GPS stations have operated at permanent Antarctic research stations, mainly along the coast, for nearly 3 decades. In contrast, deployment of continuously recording autonomous GPS instruments in the continental interior of Antarctica started mainly during the 2007-08 International Polar Year. At present, the U.S. ANET-POLENET and UK-ANET projects maintain most GNSS stations across interior and remote coastal West Antarctica and the Antarctic Peninsula; these projects have limited-term support and are currently scheduled to end within the next 2 years. Cessation of data acquisition, due to lack of operational support and/or site decommissioning, is resulting in a crucial gap in observational constraints for GIA modeling. It also hinders a range of studies using GNSS data, spanning the deep Earth to the ionosphere. Geodetic time series from autonomous GNSS systems distributed across Antarctica have revealed unexpected patterns and startling rates of crustal deformation due to GIA. Linked with seismic mapping and derived rheological properties of the Antarctic crust and mantle, and with new advances in GIA modeling capabilities, GNSS observations have transformed our understanding of the timescales of GIA response to ice sheet change. Rapid GIA response promotes cryosphere-solid earth interactions that can alter ice sheet behavior on decadal and centennial timescales, with significant implications for the contributions of marine-based sectors of the Antarctic Ice Sheet to sea level in the future. Continued progress in understanding how such feedbacks should be adopted in global sea level projections requires continuing and expanding our geodetic observations through international cooperation.
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