OCEAN:ICE will assess the impacts of Antarctic Ice Sheet and Southern Ocean processes on Planet Earth, via their influence on sea level rise, deep water formation, ocean circulation and climate. It will make new circumpolar and Atlantic observations, assimilating these and existing data into improved ice sheet boundary conditions and producing new estimates of ice sheet melt and impacts on ocean circulation. It will develop, calibrate and assess models used to predict the future evolution of the giant ice sheets. It will reduce the deep uncertainty in the impact of their melt on societally relevant environmental changes on decadal to multi-centennial time scales. It will assess the potential for passing ice sheet ‘tipping points’ and their consequences for ocean circulation and climate.