LAUSR

Using radar satellite data from the Italian COSMO-SkyMed (CSK) constellation and the German TanDEM-X formation, we present comprehensive measurements of the bi-weekly grounding line dynamics of Pine Island Glacier, West Antarctica, from August to December 2015. The one-day repeat cycle of CSK reveals tidally-induced, grounding line migration on the scale of kilometers and extensive seawater intrusion within the grounding zone, which significantly exceeds that predicted for a stiff bed but are consistent with that calculated for a deformable bed. The deformable bed also explains the continuous draining/filling of subglacial lakes proximal to the grounding line. After correction for oceanic tides, we estimate a retreat rate for 2011-2015 of 0.3 km/yr at the glacier center and 0.5 km/yr on the sides, which is three times slower than for 1994-2011 (1.2 km/yr at the center). We attribute the decrease in retreat rate to colder ocean conditions in 2012-2013 relative to 2000-2011.