OCEAN:ICE will assess the impacts of key Antarctic Ice Sheet and Southern Ocean processes on Planet Earth, via their influence on sea level rise, deep water formation, ocean circulation and climate. An innovative and ambitious combination of observations and numerical models, including coupled ice sheet-climate model development, will be used to improve predictions of how changes in the Antarctic and Greenland ice sheets impact global climate. It will make new circumpolar and Atlantic observations in observational gaps. It will assimilate these and existing data into improved ice sheet boundary conditions and forcing, producing new estimates of ice sheet melt and impacts on ocean circulation, including the Atlantic Meridional Overturning 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. OCEAN:ICE will assess the potential for passing ice sheet 'tipping points' and their consequences for ocean circulation and climate. OCEAN:ICE will raise the profile of European research through its extensive network of international collaborators, who provide scientific and logistical support. It will directly contribute to the All-Atlantic Ocean Research Alliance through observations, logistical collaboration and analysis. It will significantly advance the state-of-the-art in coupled ice sheet-climate modelling and directly contribute to international climate assessments such as the Intergovernmental Panel on Climate Change and World Ocean Assessment. It will link organically to European data centres to disseminate its data, following FAIR and INSPIRE principles. It will deliver improved assessments of European climate impacts from the melting ice sheets, with actionable risk and timescales, to policymakers and the public.