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'. 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.