But the Greenpeace claim has been disputed by the Japanese side, which said the Arctic Sunrise initiated Sunday's incident with its research vessel Nisshin Maru in waters off the Antarctic.

Differences in seawater colour could reveal how tiny Antarctic creatures are faring in a warming world. More than twice the size of greater London, the expanse of ice is unpredictable and dangerous.

The biggest base, Rothera, on the Antarctic Peninsula houses 19 winterers – the population can reach 100 in the Summer. Furthest south still is Halley VI on the Brant ice shelf where the Sun ...