We report the finding, from the GRACE observation, of an increasing trend in the gravity anomaly in Siberia at the rate of up to 0.5 mu gal yr(-1) during 2003/1 - 2009/12, in the backdrop of a negative anomaly of magnitude on the order of similar to-10 mgal. In consideration of the non-uniqueness of the gravitational inverse problem, we examine in some detail the various possible geophysical causes to explain the increasing gravity signal. We find two geophysical mechanisms being the most plausible, namely the melting of permafrost and the GIA post-glacial rebound. We conclude that these two mechanisms cannot be ruled out as causes for the regional gravity increase in Siberia, based on gravity data and in want of ancillary geophysical data in the region. More definitive identification of the contributions of the various causes awaits further studies.