High resolution Greenland ice sheet inter-annual mass variations combining GRACE gravimetry and Envisat altimetry

- Consistent inter-annual variations revealed by GRACE and Envisat in the GrIS.
- Most positive correlations are in the West, negative correlations in the Northeast.
- Nominal densities are estimated purely using geodetic observations.
- High resolution inter-annual mass variation is obtained by correcting Envisat data.

Inter-annual mass variations of the Greenland ice sheet (GrIS) are important for improving mass balance estimates, validation of atmospheric circulation models and their potential improvement. By combining observed inter-annual variations from Gravity Recovery and Climate Experiment (GRACE) and Environmental Satellite (Envisat) altimetry data over the period from January 2003 to December 2009, we are able to estimate the nominal density, with the objective of obtaining higher resolution mass changes using altimeter data at the inter-annual scale. We find high correlations between these two inter-annual variations on the order of 0.7 over 60% of the GrIS, in particular over the west side along the central ice divide. Significant negative correlations are found in parts of Northeast and Southeast GrIS, where negative inter-annual variation correlations were also found between mass change from GRACE and snow depth from ECMWF reanalysis in a previous study. In the regions of positive correlation, the estimated nominal densities range from 383.7±50.9 to 596.2±34.1 kgm−3. We demonstrate the feasibility of obtaining high-resolution inter-annual mass variation over Southwest GrIS, one of the regions with positive correlations, based on density-corrected Envisat altimetry, 2003-2009. A definitive explanation for the existence of regions of negative correlation remains elusive.