Antarctica, Greenland and Gulf of Alaska land-ice evolution from an iterated GRACE global mascon solution

We have determined the ice mass evolution of the Antarctic and Greenland ice sheets (AIS and GIS) and Gulf of Alaska (GOA) glaciers from a new GRACE global solution of equal-area surface mass concentration parcels (mascons) in equivalent height of water. The mascons were estimated directly from the reduction of the inter-satellite K-band range-rate (KBRR) observations, taking into account the full noise covariance, and formally iterating the solution. The new solution increases signal recovery while reducing the GRACE KBRR observation residuals. The mascons were estimated with 10 day and 1 arcdeg equal-area sampling, applying anisotropic constraints. An ensemble empirical mode decomposition adaptive filter was applied to the mascon time series to compute annual mass balances. The details and causes of the spatial and temporal variability of the land-ice regions studied are discussed. The estimated mass trend over the total GIS, AIS and GOA glaciers for the time period 1 December 2003 to 1 December 2010 is –380 31Gt a, equivalent to –1.05 0.09mma sea-level rise. Over the same time period we estimate the mass acceleration to be –41 27Gt a, equivalent to a –0.11 0.08mma sea-level acceleration. The trends and accelerations are dependent on significant seasonal and annual balance anomalies.