# GPS Time Series Analysis from Aboa the Finnish Antarctic Research Station
## 1 Introduction
Numerous GPS and/or GNSS (Global Navigation Satellite System) continuous and episodic stations have been established in Antarctica in the last two decades (Figure 1). The development has lead to GPS becoming an essential component of geophysical and meteorological research for studying fundamental solid Earth and atmospheric processes that drive natural hazards, weather, and climate [27]. The first GPS measurements in Antarctica were conducted in the early 90s. The main objective was to gain detailed insights into the tectonic behaviour of the Antarctic plate [28; 29]. The accumulation of the measurements allowed the definition of a precise reference frame [30]. Later, [PERSON] et al. [5] analysed GPS data from more than 50 stations across Antarctica. The authors estimated a more complete and precise vertical velocity field that allowed them to observe increase in uplift rates in the northern Antarctic peninsula after 2002-2003. Plate tectonics and vertical deformation studies also triggered the development of local or regional-scale projects [31; 32]. Long time series of continuous GPS data have been used to constrain and test the reliability of glacial isostatic adjustment (GIA) models [33; 34; 35]. Furthermore, GPS measurements in Antarctica have allowed atmospheric studies, such as ionospheric scintillation [36; 37] or ground-based water vapour retrieval [38; 39]. Aboa is an important GPS station in Antarctica due to the sparsity of bedrock sites, especially in East Antarctica. As seen in Figure 1, most of the sites are located in West Antarctica, whereas the number of sites is much lower in East Antarctica. In addition, the distances between the sites are rather large and limited to coastal regions of the continent where bedrock can be found. Furthermore, only a limited number of sites provide continuous GPS observations. As of 26 October 2018 ([[http://www.igs.org/network](http://www.igs.org/network)]([http://www.igs.org/network](http://www.igs.org/network))), there are only 13 active permanent International GNSS Service (IGS) stations [40] on the Antarctic continent and only 10 of them have longer continuous time series than Aboa. This study covers a time span of 15 years. This is two times longer than in [5] who used data for 1959 days between 2003 and 2010, whereas [42, 43] used reduced time periods. [42] covered a period of 1415 days between 2009 and 2013, while [43] analysed a time series derived for the 2010-2013 period. Furthermore, [33] computed a series of theoretical expected site velocity uncertainty for 5, 10, and 20-year long time series. Their computations show that the uncertainty decreases with the length of time series. Therefore, our results have the benefit of longer time series and thus higher reliability. Our study is the first to include an in-depth analysis of all available Aboa GPS data. The rest of the paper is as follows. Section 2 describes the material and methods used to generate and analyse the coordinates time series. Section 3 reports the numerical results of our study. Section 4 discusses the obtained results and their relationship with other published data. Section 5 summarises the main achievements, the importance of our study and the way how our work will continue.