Understanding the interplay between vertical land motion and hydrological loading in the Australian mainland

Understanding the interplay between vertical land motion and hydrological loading in the Australian mainland

This study investigates the cause of Vertical Land Movement (VLM) across the Australian mainland using 29 CORS GNSS stations operating between 2010-2022, with a focus on the role of hydrologic loading on various timescales. In addition to the corrections that are already applied to the daily VLM time series from Nevada Geodetic Laboratory, the effect of non-tidal atmospheric and ocean loadings as well as glacial Isostatic adjustment are removed from the dataset. The CSR mascon solution of GRACE and GRACE-FO data are also used to calculate the elastic loading of Earth's crust due to total water storage changes. Both VLM and hydrological loading signals are decomposed into seasonal and interannual components to analyse the role of hydrological loading in variations of the VLM. The strong correlation between the two datasets indicates that the hydrological loading is the governing factor on the seasonal timescale in most of the stations, and on the interannual timescale, there is no country-wide pattern, but significant correlations can be seen in northern Australia. We also estimated the explained variance to quantify the role of hydrological loading on both timescales, and the results indicate a trivial contribution from GRACE-estimated displacement to the variations on the interannual time scale in Western Australia and Queensland. However, this is in contrast with the fact that Western Australia experiences considerable variations on this timescale. We also estimated the linear trend of VLM over three periods of 2010-2016, 2016-2022, and 2010-2022 to see if the trend persists over time. The displacement emanating from the hydrological loading is regressed in the displacement rate estimations to remove its effect. The result shows a clear drop in the rate of subsidence in Western Australia while VLM of the stations in other areas do not present unified patterns.

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