The geodynamics of Ny Alesund from ITRF2014 time series

We have derived the kinematical motions of Ny-Ålesund, Svalbard, comparing recently published ITRF2014 coordinate time series from VLBI, GPS, and DORIS. Earlier studies have revealed inconsistent results between different observing techniques, mainly due to non coherent processing strategies and different detection, handling and estimation strategy of the discontinuities. Offset detection and estimation still remain a critical issue in order to further reduce offset-related velocity biases. The harmonic analysis shows also some differences in the detected periodic signals frequency, phase and amplitude, that are clearly of non geophysical origin.

The adopted analysis method models time series as discrete-time Markov processes. This approach is particularly well suited to better describe the long-term signal, particularly in case of nonlinearities in the time series when also the multilinear velocity models are not adequate. Time series offsets and long-term trends were estimated to obtain the quasi-cyclostationary residuals needed to conduct the harmonic analysis. Documented first-order discontinuities were assumed a priori as candidate discontinuity epochs, whereas other discontinuities were detected, thus adding dedicated variables to the original state–space model of the time series. The coordinate offsets were estimated and tested for statistical meaningfulness.