Ice streams and outlet glaciers are important components of an ice sheet’s mass balance and their behaviour directly impacts on sea level. These corridors of fast-flowing ice have been described as the ‘arteries’ of an ice sheet and their distinction is largely semantic, with ice streams bordered by slower-moving ice and outlet glaciers bordered by exposed bedrock at the surface. Since the recognition of the importance of these features in the 1970s, there has been a huge growth in their investigation. This began with the pioneering work on West Antarctic ice streams and has subsequently expanded to studies of ice streams and outlet glaciers in all of the world’s major ice sheets and ice masses. Of urgent concern for society are recent observations of dynamic changes in ice streams and outlet glaciers, which are thought to be responsible for an acceleration in global eustatic sea-level rise.

In parallel, those studying palaeo-ice sheet beds have long-recognised the distinctive geomorphology of ice streams in both marine and terrestrial settings. The study of palaeo-ice streams offers an unprecedented opportunity to reconstruct their behaviour over time-scales much longer than modern observations permit, generating new insights into the spatial and temporal controls on their flow, including longer-term perspectives on retreat rates and thinning histories. The beds of palaeo-ice streams and outlet glaciers are also more accessible for investigation, leading to new insights regarding the mechanisms of sediment erosion, transport and deposition beneath fastflowing ice, including the formation of subglacial bedforms.