Fig. 4

Concept of interference of seasonal land and ocean mass changes (c) of comparable amplitudes but with phase lags (a). Horizontal (landward) movement reflects the difference between the land and the ocean masses, while vertical movement reflects the sum of both (b). In case 1 (left), 2 (middle), and 3 (right), the two masses change in phase, with phase lags of 90 and 180 degrees, respectively. In these cases, coastal GNSS stations show only vertical (Case 1) and horizontal (Case 3) displacements (green arrows). In Case 2, both horizontal and vertical seasonal crustal movement occur with different phases, and station movement trajectory becomes an ellipse. This occurs in the Gulf of Carpentaria in northern Australia (Zheng et al., 2023)