Sea level monitoring from POLENET and GNET GNSS networks

POLENET and GNET global navigation satellite system networks are installed to study solid Earth and ice mass changes in Antarctica and Greenland, respectively. Geodetic-quality antennas are designed to boost the energy from the satellite transmitter and to suppress the reflections. But it is still possible to receive both the direct and short delayed surface reflections simultaneously. Although this multipath reception condition is one of the main error sources in high-precision GNSS studies, the temporally constructive and destructive oscillations in the recorded signal-to-noise ratio interferograms can be used to retrieve environmental variables such as sea level. Here, SNR observations from commercial off-the-shelf systems are used to estimate sea level in Antarctica and Greenland. After correcting the retrieved reflector heights for the propagation delay of microwave signals from GNSS satellites to ground-based receiver, water levels are retrieved applying two methods. In the first method, we correct the retrieved heights for the vertical velocity to consider the dynamic state of the sea and in the second method tidal parameters are estimated that allows us to determine the vertical velocity directly.