Observing and assessing nontidal ocean loading using ocean, continuous GPS and gravity data in the Adriatic area

The effect of nontidal ocean loading (NTOL) is observed in the height series of four permanent GPS stations in the northern Adriatic. A validation of the ECCO model is performed by comparing model estimates of sea-level anomalies from tide-gauges with TOPEX/POSEIDON data, and ECCO model estimates of bottom pressure with those derived from temperature and salinity observations. The amplitudes of the ECCO sea-level anomaly are found to be 1.4 times smaller than observations; bottom pressure is 2 times smaller. Using a Green's functions approach to determine elastic deformations, the ECCO ocean bottom pressure is used to estimate surface displacements at the GPS sites. Model results were compared with the height series and with the observed NTOL effect. The height series and the predicted NTOL are highly correlated at all four stations. The analysis performed on superconducting gravimeter data at the Medicina station also shows high correlation.