Wind-driven coastal polynya variability drives decadal ice-shelf melt variability in the Amundsen Sea

The ice shelves in the Amundsen Sea, West Antarctica, are being melted rapidly by warm Circumpolar Deep Water (CDW), causing sea-level rise. Variability in ice-shelf melting is controlled by the speed of a shelf-break undercurrent which transports CDW from the deep ocean onto the continental shelf. We study decadal variability of the undercurrent and ice-shelf melting using new regional ice-ocean model perturbation experiments. The perturbation experiments suggest that the undercurrent decadal variability is controlled by variable coastal sea-ice freshwater fluxes, these driven by winds mechanically opening and closing coastal polynyas. With the perturbation experiments we also quantify a positive feedback mechanism between the undercurrent and ice-shelf melting which is responsible for 25% of their decadal variability.