Ian Allison is a glaciologist who has greatly advanced our understanding of the role of Antarctica and sea ice in climate variations. He pioneered the study of Antarctic sea ice with innovative and challenging year-round field campaigns, which documented for the first time the seasonal variation in growth, redistribution, and decay of sea ice through its interactions with the atmosphere and underlying water column. He has also shown the importance of melt and refreezing beneath ice shelves to mass loss from the ice sheet, and vulnerability to ocean change. He has been an outstanding leader of the Australian Antarctic program and international polar research collaboration over many decades, including co-chairing the peak committee responsible for the 2007-2008 International Polar Year.