John Fletcher (left), a PHD student in polar oceanography at Cambridge University, measures the undulations of the crystalline structure of the ice and snow surface layer in fine detail by using a laser to obtain a 'topographical profile'. For the laser to work, the surrounding area must be dark, hence the black hood around his work area. His work is concerned with making ground calibrations for 'cryosat' a new European satellite that has radar capability to measure ice thickness. He is part of a team of scientists working with the Greenpeace crew, researching the effects of climate change on fast depleting sea ice.