Antarctic ice-shelf thinning drives 21st-century changes in global tides

Current projections of water levels by the end of the 21^st century assume that secular trends in ocean tides are solely caused by sea-level rise (SLR). Here we use a barotropic tide model and ocean bathymetries adjusted along climate trajectories to show that such projections confined to SLR will underestimate the change in ocean tides if Antarctic ice-sheet melt alters the geometry of sub-shelf cavities through which the tide propagates. Perturbations to the year-2000 control bathymetry include both water depth and basin shape changes, constructed from aggregated spatial projections of sea-level components and time-varying Antarctic cavity geometries from an external ice-sheet model. Under the Representative Concentration Pathway 8.5 scenario, we find end-of-century anomalies in the amplitude of the principal semidiurnal tide of +20 cm on the Patagonian Shelf, +4 cm in the Tasmanian Sea, and -3 cm on the European Shelf, substantially modifying or even outpacing the tidal response to SLR. The broad pattern of this change is conclusively linked to widespread thinning of Filchner-Ronne Ice Shelf, which attenuates local dissipation and re-organizes amphidromic systems around the globe. The study thus illustrates another relevant facet of tidal dissipation in the Earth system and underlines the need for a multi-component modeling framework when estimating future sea-level extremes.