Crossing a crack in the Arctic ice
The Arctic is the fastest warming region on Earth.
If the polar ice retreats it could accelerate the rise in global temperatures and significantly change the world's weather patterns.
A team of Norwegian scientists has spent the winter on a research ship in the Arctic examining the sea ice. They say it is becoming thinner and more likely to break up.
The BBC's science editor David Shukman has been aboard their ship and reports on their Arctic mission.
You can see the report in full on Our World: Arctic Mission with David Shukman on BBC World News on Friday 8 May at 23:30 and Saturday 9 May at 11:30 and 22:30 GMT. In the UK the programme can be seen on the BBC News Channel on Saturday 9 May and Sunday 10 May at 21:30 BST.
08 May 2015