SCAR INSTANT is a research programme of the Scientific Committee on Antarctic Research (SCAR) that focuses on understanding Antarctic ice sheet instabilities and their contribution to sea level changes, from the deep past to the future. The aim of INSTANT is to bridge communities, e.g. to try to bridge paleo-evidence and process-based development (for example, marine ice sheet instability (MISI), marine ice cliff instability (MICI), grounding line dynamics, ice–ocean interactions). The aim of the special issue is to reflect this process: what do we know from paleo-observations and present observations that can help to improve the physics; where are big modelling and observational gaps in ice sheet, ocean, and atmosphere physics; and what are the advances in paleo-proxies, present observations, methodologies, etc.? The various contributions should be community-driven and not single-author contributions. The papers should focus on the Antarctic system, thus focusing on atmosphere, the ocean, ice sheets, and bedrock and beneath and on the interactions between those components, from paleo-perspectives to the future. Global connections with Antarctica (teleconnections, inter-hemispheric processes) are also welcome. An important part of the SCAR INSTANT programme is the science-to-policy topic. As such, this special issue also welcomes policy-driven, actionable scientific contributions as well as social science studies.