GNSS processing in Northern Italy at hourly sampling rate, gravity, and detection of the Ocean tide loading

Ocean tides especially in closed sea areas can deviate significantly from the theoretical values due to the bathymetry. Even though the amplitudes of the ocean tides in the Mediterranean Sea are relatively small, the availability of the best tidal model is essential for geodetic and geodynamic applications. We analyse different types of geodetic techniques to investigate current ocean tidal models (FES2014b, EOT20, TPOX9-Atlas) for the Adriatic Sea, eventually to further refine the ocean-tide model for this particular area. The data used are GNSS double difference products at hourly sampling rate obtained from processing with GNSS Bernese software. The 60 stations processed over a one-year timespan are collected from different European networks. Furthermore, we process tide gauge observation along the Adriatic coast. Gravity data collected from two relative gravimeters located in the Skocjan cave (Slovenia) are used as a control of the ocean tide models. By testing two weeks of GNSS data, we discovered a discrepancy in amplitudes and phases for the horizontal components between the observations and the predicted model for FES2014b, while the observed vertical component presents good coherence with the model. We believe that by expanding the timespan interval of observations, investigating other global ocean loading models and adding gravity data, we should be able to obtain a clearer understanding of the identified discrepancies. In a second step, the analysis looks at the detection of non-tidal loading high stance effects present in GNSS and gravity time series, an important condition for the estimation of accurate rates of the Earth’s crust movement in the studied area.