Surface elevation and velocity changes on the south-central Greenland ice sheet: 1980-2011

We extend through 2011 an ice-sheet elevation and surface velocity record across three measurement networks established in south-central Greenland by The Ohio State University in 1980/81. Surface parameters are derived from repeat GPS in situ observations, elevations measured by airborne laser altimetry and by the Ice, Cloud and land Elevation Satellite (ICESat). Elevations at the western network steadily rose early in the record by 0.10 +/- 0.02 m a(-1), but an eastward-progressing thinning trend began in the mid-1990s followed by a similar to 1 m elevation drop at all stations from 2005 to 2011. Measurements weakly suggest a surface velocity increase at the western cluster from 1980 to 2005. At the central network, elevations rose by 0.08 +/- 0.02 m a(-1) through 2005 and surface speed increased by 0.5-0.7 m a(-1). Surface elevations at the central network remained nearly constant thereafter. Thickening occurred at the southern ice divide by 0.05 +/- 0.02 m a(-1), while east of the divide the ice sheet thinned with increasing rate from the divide, likely because of decreasing accumulation rate trends and drawdown into rapidly retreating coastal glaciers. Our most recent data show that thinning rates are slowing at several sites just east of the divide and that the elevation at the divide continues to increase.