The marine portion of the West Antarctic Ice Sheet (WAIS) in the Amundsen Sea Embayment (ASE) accounts for one-fourth of the cryospheric contribution to global sea-level rise and is vulnerable to catastrophic collapse. The bedrock response to ice mass loss, glacial isostatic adjustment (GIA), was thought to occur on a time scale of 10,000 years. We used new GPS measurements, which show a rapid (41 millimeters per year) uplift of the ASE, to estimate the viscosity of the mantle underneath. We found a much lower viscosity (4 × 10 pascal-second) than global average, and this shortens the GIA response time scale from tens to hundreds of years. Our finding requires an upward revision of ice mass loss from gravity data of 10% and increases the potential stability of the WAIS against catastrophic collapse.

We present preliminary geodetic estimates for vertical bedrock velocity at twelve survey GPS stations in the West Antarctic GPS Network, an additional survey station in the northern Antarctic Peninsula, and eleven continuous GPS stations distributed across the continent. The spatial pattern of these velocities is not consistent with any postglacial rebound (PGR) model known to us. Four leading PGR models appear to be overpredicting uplift rates in the Transantarctic Mountains and West Antarctica and underpredicting them in the peninsula north of 65°. This discrepancy cannot be explained in terms of an elastic response to modern ice loss (except, perhaps, in part of the peninsula). Therefore, our initial geodetic results suggest that most GRACE ice mass rate estimates, which are critically dependent on a PGR correction, are systematically biased and are overpredicting ice loss for the continent as a whole.

We identified coseismic ionospheric disturbances (CID) in Antarctica generated by the 2010 Maule and the 2011 Tohoku‐Oki earthquakes analyzing total electron content (TEC) data with a modified beamforming technique. Beamforming in Antarctica, however, is not straightforward due to the effects of array deformation and atmospheric neutral wave‐ionospheric plasma coupling. We take these effects into account and present a method to invert for the seismically generated acoustic wave using TEC observations. The back azimuths, speeds, and waveforms obtained by the beamform are in excellent agreement with the hypothesis that the TEC signals are generated by the passage of Rayleigh waves from the Maule and Tohoku‐Oki earthquakes. The Tohoku‐Oki earthquake is ~12,500 km from Antarctica, making this the farthest observation of CIDs to date using GPS.

We present a new record of crustal deformation for the Dry Valleys and surrounding region of Antarctica. Values of crustal tilt resulting from the differential uplift of lacustrine strandlines are derived and linked with age data to provide a history of solid earth deformation since deglaciation. We present tilt directions and gradients for 13 strandlines formed c. 18 100-2100 cal yr BP. Derived gradient magnitudes increase exponentially with age and indicate an ongoing response to deglaciation since the Last Glacial Maximum. Azimuths of crustal tilting are consistently down to the SE towards West Antarctica. This tilt pattern is opposite to that predicted by models of glacial isostatic adjustment for Antarctica. Tilt magnitudes are significantly larger than tilted strandlines documented elsewhere in the world, suggesting an influence from thin crust and weak mantle underlying the region. This study presents the first use of lacustrine strandline tilts to document crustal deformation due to glacial unloading in Antarctica and provides an important new datum for constraining glacial isostatic adjustment models.

<p>ANET-POLENET (Antarctic Network of the Polar Earth Observing Network) bedrock GNSS sites in the Ross Sea region of Antarctica surround an LGM load center in the Siple region of the Ross Embayment and record crustal motion due to GIA.  Rather than a radial pattern of horizontal motion away from the former load, we instead observe three primary patterns of deformation; 1) motions are reversed towards the load in the southern region of the Transantarctic Mountains (TAM), 2) motions are radially away from the load in the Marie Byrd Land (MBL) region, and 3) an overall gradient in motion is present, with magnitudes progressively increasing from East to West Antarctica.  We investigate the effects of alternative Earth model and ice loading scenarios, with the goal of understanding these distinct patterns of horizontal bedrock motion and their drivers. Using GIA models with a range of 1D Earth models, alternative ice loading scenarios for the Wilkes Subglacial Basin (LGM time scale) and the Siple Coast (centennial and millennial time scales) are explored.  We find that no 1D model, regardless of the Earth model and ice loading scenario used, reproduces all three distinct patterns of observed motion at the same time.  For select ice loading scenarios we also examine the influence of more complex rheology by invoking a boundary in Earth properties beneath the Transantarctic Mountains.  This approach accounts for the strong lateral gradient in Earth properties across the continent by effectively separating East and West Antarctica into two different Earth model profiles.  Some of our GIA models utilizing 3D Earth structure reproduce predicted motions that match all three observed patterns of deformation, and we find that a multiple order magnitude of change in upper mantle viscosity between East and West Antarctica is required to fit the observations. </p>