The kinematics of Ny-Ålesund from space geodetic data

We have compared coordinate time series from several space geodetic observing techniques to derive the kinematical motions of Ny-Ålesund, Svalbard. Velocity estimates from VLBI, GPS, and DORIS scatter more than the expected error estimates from each technique, and also between individual GPS solutions with different software and analysis strategies. A statistical combination yields average topocentric velocity components of 14.3±0.214.3±0.2 mm/year (north), 9.8±0.79.8±0.7 mm/year (east), and 8.2±0.98.2±0.9 mm/year (vertical) for 1993–2007. The horizontal velocity is in agreement with a combined prediction of NUVEL-NNR-1A and the effects of post-glacial rebound and present day ice melt of nearby glaciers. The observed uplift is twice that predicted by the two latter processes. The non-linear time series of both VLBI and GPS data suggest that the uplift rate increases from 7.0 mm/year before 2003 to 10.8 mm/year after 2003. We conclude that this has a geophysical origin since no monument motions have been detected. A recent sea level decrease (1993–2007) of 4.7±0.94.7±0.9 mm/year supports an absolute sea level increase of 3.2 mm/year as determined elsewhere by satellite altimetry.