Researchers: Valentina R. Barletta, Technical University of Denmark and Ohio State University, Michael Bevis, Terry Wilson, Abel Brown, Eric Kendrick, Stephanie Konfal and Dana J. Caccamise II, Ohio State University, Benjamin E. Smith, University of Washington, Andrea Bordoni and Shfaqat Abbas Khan, Technical University of Denmark, Michael Willis, University of Colorado, Marc Rovira-Navarro, Technical University of Denmark and Technical University of Delft, Ian Dalziel, University of Texas, Robert Smalley Jr., University of Memphis, Richard C. Aster, Colorado State University, Andy Nyblade, Penn State University and Douglas A. Wiens, Washington University.
Written by Linda Rowan
26 October 2018
The West Antarctic Ice Sheet is melting and the ice loss causes the land surface to rise up in a process called glacial isostatic adjustment (GIA). GPS measurements in the Amundsen Sea Embayment (ASE) show a rapid rise of as much as 41 millimeters per year; more than expected. One reason for the rapid rise is a softer, more pliant mantle beneath the land surface. These results suggest that the ice loss is more significant than previously realized with gravity measurements and this may have implications for global sea level change forecasts.
Antarctica is a very large continent that is mostly covered by a massive ice sheet. Along the coast, the changes in the ice sheet are significant, especially the ice loss. Along the coast and other places where bare rock is exposed, GPS monuments have been installed to measure the horizontal and vertical motion of the land surface. The observations are helping to measure the amount of GIA that has occurred over decadal scales.
The West Antarctic Ice Sheet has shown the most dramatic changes over many decades and the marine portion of the ice sheet in the ASE accounts for one quarter of the cryospheric contribution to global sea level rise. A network of six GPS monuments installed in the bedrock in and around the ASE provided observations of these changes. Using a new processing technique for global geodetic data and a more complex model of mantle viscosity, the researchers constrained the GIA signal and the Earth structure below the ASE.
The six GPS sites measured significant, as high as 41 millimeters per year, over a 13-year period of measurement (2002 to 2014). A higher resolution model with a more complex viscosity structure in the mantle can be fit to the measurements if the mantle has a very low viscosity (that is, if the mantle is more pliant with a greater capacity for flow). A softer mantle allows for greater uplift for a given ice mass loss. Compellingly, these results indicate that the ice mass loss rate is much higher than previously measured with gravity. The new Earth structure found in ASE has implications for global sea level change and other environmental factors.
Observed rapid bedrock uplift in Amundsen Sea Embayment promotes ice-sheet stability, V. Barletta et al., Science 22 Jun 2018: Vol. 360, Issue 6395, pp. 1335-1339, doi:10.1126/science.aao1447.
viscosity, glacial isostatic adjustment, global sea level rise
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