Comparing Non-Tidal Ocean Loading Around the Southern North Sea With Subdaily GPS/GLONASS Data

Abstract

Observing subdaily surface deformations is important to the interpretation of rapidly developing transient events. However, it is not known whether Global Navigation Satellite System (GNSS) is able to identify millimeter-level transient displacements over various subdaily timescales. We studied non-tidal ocean loading (NTOL) using 18 GNSS stations along the southern North Sea for November–December 2013 and compared 3-h GPS/GLONASS displacements with NTOL predictions. It was found that they overall agreed well with a mean correlation coefficient of 0.6 and their vertical differences had an RMS of 5.7 mm, but a 10-mm subsidence prediction for December 5th could only be marginally detected. Hence, the spatial coherence among the loading signatures at the 18 stations was harnessed to improve subdaily GNSS, and then the predicted displacements of 5–10-mm over the subdaily timescales could be discriminated successfully. We envision that adding Galileo/BeiDou signals to GPS/GLONASS can further improve the resolution of subdaily GNSS, which can also enhance the spatial coherence of transient signals captured by regional GNSS stations.