The latest video from the British Arctic explorers trekking across the sea-ice illustrates the severity of the conditions in which they are working.
The Catlin Arctic Survey team, led by Pen Hadow, is measuring the thickness of the ice.
But the three individuals who make up the group were down to just one day's food rations, in temperatures as low as -40C with wind chill, before vital supplies reached them by plane.
But their problems did not end there. As Pen Hadow explains, the team awoke recently to discover the ice cracking up around its camp.