Sea Level Rise and Loading Deformation in the Shallow Seas of Northern Australia

The northern shallow seas of Australia exhibit significant interannual mass variations driven by complex oceanographic and hydrological processes. While large-scale oceanographic and hydrological mechanisms in this region are well studied, the specific contributions of individual processes to these variations require further quantification. To this end, we employed satellite gravity, satellite altimetry, and Global Navigation Satellite System (GNSS) to investigate sea level changes and their loading effects from 2003 to 2022. Our results reveal that strong colored noise significantly affects GRACE-derived mass trend estimates, emphasizing the need for spatially varying noise models. We also find that sea levels in the northwestern sea and the Gulf of Carpentaria (GOC) have risen steadily, primarily due to the increase in ocean mass (0.50 ± 0.20 and 0.46 ± 0.24 cm/a, respectively). Monsoons and associated rainfall drive the increase in water mass in GOC, while ocean currents outside the GOC also significantly influence the mass changes. A net mass outflow is observed during the four summer months (261.5 ± 105.4 Gt), while the remainder of the year shows a net inflow (333.6 ± 51.8 Gt). In addition, vertical displacements from nine GNSS stations around the GOC were used to independently retrieve daily mass variations from 2017 to 2021. The GNSS-derived mass variations exhibit consistency with GRACE in both seasonal and interannual variability and offer enhanced temporal resolution.