Recent postglacial rebound, gravity change and mantle flow in Fennoscandia

The recent postglacial rebound of Fennoscandia is investigated using sea-level data, levelling data and gravity data. In particular, an analysis is made of the repeated data obtained hitherto on the Fennoscandian land-uplift gravity line along latitude 63 degrees. Methods for this analysis include an iterative procedure for computing the relation between gravity change and absolute land uplift, the mass-flow parameter and the geoid rise; the remaining land uplift is also estimated. The mass-how parameter c is used to characterize the relation between additional mass and additional volume due to rebound; it is a number between 0 and 1, 1 corresponding to full inflow of mantle below the rising crust, and 0 to no inflow but some kind of decompression. The main result is that c is significantly different from 0 at the 99 per cent level: we find c approximate to 0.8. This means that models proposed of the present uplift based on pure decompression must be ruled out, and that a viscous inflow of mantle is a necessary part of the ongoing uplift process. On the other hand, this process might be more complicated than a pure viscous flow.