Annals of Glaciology Collection ‘Sea Ice Across Temporal and Spatial Scales’ contains 21 timely contributions about sea-ice properties and processes, considering its variability and change on various temporal and spatial scales, from the micro- to the global scale. These are most relevant given the rapid retreat of Arctic and Antarctic sea ice. Many of the included papers were also presented at the International Glaciology Society’s International Symposium on Sea Ice Across Temporal and Spatial Scales, which took place in Bremerhaven, Germany, in June 2023.