Decadal variability of ice-shelf melting in the Amundsen Sea driven by winds

Ice shelves in the Amundsen Sea, West Antarctica, are being melted rapidly from below by warm ocean waters, causing sea-level rise. Amundsen Sea oceanography and ice-shelf melting are both subject to long-term (centennial) trends and natural decadal variability. We study the atmospheric drivers of the decadal variability using perturbation experiments in which the mechanical (winds) and thermodynamic atmospheric forcings are applied individually in an ice-ocean model of the Amundsen Sea. We find that the decadal variability is predominantly driven by mechanical forcing of the winds, through impacts on the melting and formation of sea ice. This variability in the sea ice drives variability in the Amundsen Sea undercurrent and the heat fluxes towards the ice shelves, which in turn leads to decadal variability in the melting of the ice shelves. While winds are the primary driver of this variability, it is also found that a significant part of the variability is due to nonlinear effects, and cannot be explained by the individual impacts of either winds or thermodynamics. Our results also highlight how the processes that drive variability differ depending on the timescale (e.g., annual, decadal, centennial) of interest.