The northern shallow seas of Australia exhibit significant interannual mass variation characteristics. The sources and physical mechanisms underlying these variations are not fully understood and warrant further investigation. To this end, we utilized satellite gravity, satellite altimetry, and Global Navigation Satellite System (GNSS) to study and analyze sea level changes and their loading effects in this region from 2003 to 2022. The results indicate that sea levels in the northwestern sea and the Gulf of Carpentaria (GOC) have been continuously rising, primarily due to the increase in ocean water mass (0.37±0.05 cm/a and 0.43±0.07 cm/a, respectively). The contribution of oceanbottom deformation caused by mass changes to sea level rise accounted for 4% and 5%, respectively. However, using reanalysis products to study the steric sea level results in significant errors, leading to an underestimation of the annual amplitude by 63%. Monsoons and monsoon rainfall drive the increase in water mass in GOC, while ocean currents outside the GOC also significantly influence the mass changes, with an annual total outflow flux of 72.09 Gt. We also found that a single GNSS station on island within the GOC can effectively capture the seasonal and interannual water mass variations in GOC. For seasonal changes, the correlation between vertical displacement and gulf mass variation reached 0.90, and the station was able to recover 72.7% of the interannual amplitude of long-term ocean mass changes in the GOC.

The variations in the lake water storage in the Tianshan region are an important indicator of climate change and play a key role in understanding the hydrological mass balance. Based on altimetry and satellite gravity, we investigated the spatiotemporal characteristics of the lake water storage changes during 2002–2022, and examined the contributions and proportions of all of the hydrological components to the mass balance. The results indicate that the total water storage of the lake complex showed an increasing rate (0.73±0.10 Gt/a). We found two abrupt wet periods in 2010 and 2016 (the regional total mass increased by 65.73 Gt and 67.35 Gt, respectively), which were reflected not only by the lake water storage but also by the soil moisture, snow water, and even GNSS displacement fields. Compared with their contributions to the mass (22% and 14%), the variations in lake area were remarkably slight (0.01% and 0.014%). Among the hydrological components, the soil moisture played a dominant role, and the contribution of the snow accumulation changes was also considerable. The mass anomalies were closely related to the precipitation caused by the increase of water vapor content, which was further associated with the occurrence of ENSO events (r=0.55, p<0.01). The results revealed that the long-term trend of the GNSS vertical displacements exhibited a better stability after the load correction was applied, which could reflect the long-term ground deformation more accurately. This study contributes to our understanding of the complex hydrological and tectonic processes in the Tianshan region.