Summary
The CRAC-ICE project aims at monitoring the calving of the Mertz Glacier tongue in East Antarctica, an ice tongue which extends 140km from its grounding line. Legresy et al. (2004) observed dramatic ice flow changes at daily scales linked to tide currents using limited GPS observations and inSAR. During the French Antarctic program in 2007, we deployed a network of year-round GPS beacons along a flow line of the glacier, including upstream of the grounding line, the upper part of the ice tongue each side of the main rift and near the glacier front. Two GPS were also installed on rock sites each side of the glacier. Two months of GPS data were collected at the end of the field season from 2 stations (GPS4 & GPS5) around the main rift. We have analyzed ERS SAR, Landsat images, Radio echo sounding (taken during the Italian Antarctic program in 1999, 2001 and 2003) and the GPS data together to draw an overall description of the rifting and calving process. We draw the history of this rifting. We monitored the development of the rift over 13 years. The ice tongue is freely floating and has horizontal motions of about 3m/d, rift opening of 12cm/d, it’s rotating Eastward since 2002 and. The ice flow and rifting are modulated at daily to fortnightly scales with tides and currents, a lag is observed between spring tides and fastest ice flow suggesting lubrication. Finally we observe stretching induced thinning of the area near the rift opening.