Antarctica seasonal mass variations detected by GRACE

The newly available GRGS-EIGEN-GL04-30day solutions computed by the GRGS group in Toulouse are used to study inter- and intra-annual mass variations in Antarctica. The series of gravity coefficients cover the period from July 2002 to March 2005. They are corrected for ocean tides, ocean high frequencies and atmospheric pressure, so the remaining signal mostly comes from ice mass variations and post-glacial rebound. The errors of these fields are estimated to be less than 2.4 cm of water height equivalent, with punctual values of only 0.5 cm. The polar Antarctica zone benefits from a low error level, which compensates for the weak gravity variations. The temporal signal computed over the whole continent shows a clear seasonal cycle, with a maximum of precipitation during winter months and a minimum during summer months. The ratio between winter and summer snow precipitation is also estimated to be 2.75 which accords well with previous studies. The gravity fields are developed to provide suitable information up to 666 km. The study could therefore focus on regional areas. The coastal zones exhibit higher variable signals with stronger snow accumulation rates than the central part, in agreement with climatologic models and in situ observations. The peninsula zone has the highest values, with a clear semi-annual component.