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Mark Brandon, The Open University

You never forget the first time you see an iceberg. The horizon of a ship at sea is a two dimensional space and to see a three dimensional piece of ice appear in the ocean is quite something. But, in truth, the first iceberg you see is likely to be small. Most icebergs that make it far enough north from Antarctica to where they are danger to shipping are sometimes many years old and at the end of their lives. They are small fragments of what once left the continent.

Once in a while, however, a monster breaks free from the edge of Antarctica and drifts away. Tens of kilometres long these bergs can tower perhaps 100 metres above the sea and reach several hundred more below the surface. These are called tabular icebergs – and while it is rare for humans to see something on such a scale they are part of the normal cycle of glacial ice in Antarctica.

A tabular iceberg gets stuck in thin, seasonal sea ice.
Mark Brandon, CC BY-NC-SA

Everyone knows Antarctica is an ice-covered continent, but the ice is not static. To a scientist it is a dynamic environment – it’s just a question of the timescale you are looking at. Snow falls on the continent and over time it has built up layers of ice which flow in glaciers towards the coast.

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