Towards closing the Australian vertical land movement budget

GPS analysis of Australian vertical land motion (VLM) consistently suggests widespread subsidence of Australia of about 1-1.5mm/yr since ~2000, in contrast to most models of Glacial Isostatic Adjustment which predict motion closer to zero or slightly positive. These GPS findings have been corroborated by estimates from altimeter-minus-tide gauge measurements, suggesting they are robust within their terrestrial reference frame. Here we revisit the potential causes for this misfit, exploring a new reconstruction of global ice-loading changes and its impact on vertical land motion. We show this likely produces a subsidence of Australia of about 0.5mm/yr. We explore this in combination with estimates of hydrological, atmospheric and non-tidal ocean loading displacements. The residual signal is discussed within the context of different GIA model predictions, reference frame errors, and the possible impact of far-field postseismic signal.