Should you want to annoy a glaciologist, ask a simple question: which are the largest glaciers in the world? The answer has long been: it depends how you define a glacier.
Do glacier complexes, made up of several connected glaciers, count as one? And what is the best way to map the outlines of these massive bodies of ice?
Ann Windnagel at the US National Snow and Ice Data Center in Boulder, Colorado, and her colleagues took up the challenge of ranking the world’s glaciers by area1. The researchers drew on data from two glacier inventories; if the values for a glacier’s size differed, the authors chose the most recent measurement or, if the dates were the same, averaged the two. They also merged glaciers into a complex if the glaciers shared boundaries with one or more others, however small those connections were.
Their ranking shows that the world’s largest individual glaciers by area are found in the Antarctic, led by the Seller Glacier (7,018 square kilometres). On other continents, the largest glaciers are in Alaska and the Canadian Arctic. The largest glacier complexes are also in the Antarctic and the Arctic. Outside the polar regions, the Southern Patagonian Icefield is the largest glacier complex.
