Sea Tide Analysis Derived by PPP Kinematic GPS Data Acquired at David-Drygalski Floating Ice Tongue (Antarctica)

One of the most important ice-stream of the Victoria Land (VL) is the David Glacier, which produces 100 km long floating sea-ward ice tongues in the Ross Sea, the Drygalski Ice Tongue (DIT). The ice-tongue slides down into the sea increasing its velocity rates and together with ice-stream movement sometime produce characteristic ice-quakes. This paper shows the effects of the sea tidal variation on both horizontal and vertical components of movement at a portion of DIT. Ocean tide is usually modelled by a series of harmonic coefficients (amplitude and phase), which are estimated through several systems of measurement. For the study area, these data are made available by the Antarctic Tide Gauge (ATG) database. Moreover, tidal data recorded by a multiparameter underwater tide gauge, which was installed at Mario Zucchelli Station (MZS), the Italian Antarctic Base, in February 2006, are being processed again. The kinematic Precise Point Positioning (PPP) processing was adopted for the analysis of 24 days of acquisition performed with a GPS receiver located in the initial part of DIT, about 46 km seaward from the Ice Fault David Cauldron. The analysis of harmonic tidal components has shown that PPP solutions show correct values of diurnal and semi-diurnal tidal components and therefore can provide valuable information in the coastal area covered by ice tongues.