When 40 British pupils charge into the icy Arctic Ocean, surrounded by three gunmen to ward off potentially lethal polar bear attacks, you know this is no ordinary field trip. "Oh my God, it is absolutely freezing," cries Jess Fok, 17, from Eltham College in south-east London, as she dunks her head under the water and manages two brisk strokes before rushing out on to dry land. "It's the sort of cold that actually causes you pain."
But the chill factor out of the water is probably worse. Even on a "warm" summer day in the Arctic when it is 5 degrees C, an average 10 metres-per second wind will drop the temperature to - 7.7 degrees C.
However, the memories from that dip are likely to last much longer than the cold. In fact, most things about this week-long trip are unforgettable be it swimming in the Arctic, glimpsing whales or walking on thousand-year-old icebergs in one of the most remote and eerily beautiful places in the world.
The 13 to 17-year-old pupils are all winners of a UK-wide competition organised by Edge, the educational foundation which promotes vocational and practical learning. More than 4,000 pupils entered the competition, which challenged them to devise practical solutions to environmental problems. Their ideas ranged from a power station that burns sulphur instead of coal, to an eco-lock which shuts off power to home appliances when you lock the front door.
The winning youngsters first fly to Svalbard, an archipelago in the Arctic Ocean roughly midway between Norway and the North Pole. There the "learning through doing" begins, with pupils studying the impact of global warming alongside professional climate scientists.
The Arctic is particularly vulnerable and is cited as an early warning sign to the rest of the planet. For the past two years, many of the fjords have failed to freeze over as usual. Lewis Pugh highlighted the point when he became the first man to swim at the geographical North Pole earlier this month an impossible feat 10 years ago when the water would have been entirely covered with thick ice. Lasting 19 minutes in the - 1.8C water, the maritime lawyer and environmental campaigner from London used the swim to draw attention to global warming. Scientists predict that by 2040, the Arctic could be virtually ice free in summer.
It is a message brought home by Geir Gaprielse, one of the world's most prominent Arctic biologists. He joins the schoolchildren on Polaris, their home for the week, a ship more used to hosting Vladimir Putin, the Russian President, than a gaggle of British schoolchildren.
"We must recognise the effect of pollutants and contaminants on the planet," he warns. "Go home and become responsible consumers. The way we all behave will have a direct effect on the Arctic's future."
The next stop on their journey north is Ny-Alesund. Once an old mining port, it is now home to 14 different research stations and about 100 international scientists. Welcomed by Nick Cox, of the British Antarctic Survey, the pupils are split into groups and given hands-on lessons in marine biology, ornithology, Arctic art and the area's history.
One of the groups helps Dr Nia Whiteley from the University of Wales in Bangor with her research into the tiny, shrimp-like arthropoda crustacea. "We collect the species, measure their metabolic rates and the effect temperature has on them," she tells pupils as they look for them under rocks. "We have found they are very sensitive to temperature change, which could be a problem for them as the water warms up."
The residents of Ny-Alesund take eco-consciousness to new levels. No one is allowed to walk on grass or vegetation and there are 28 different ways of recycling waste. Appreciating their thoughtful human neighbours is an Arctic fox and her cubs roaming outside. After cooing over them, it is time for the pupils to buy postcards from the most northerly shop in the world, before posting them at the most northerly post office in the world. Unfortunately for the teachers, the most northerly pub is not open for business.
Back on the ship, the floating lessons involve collecting plankton, sea life and ice, before studying them under the microscope with Claudia Helsband-Lenk, a marine biologist, and Sebastian Barrault, an Arctic technologist.
"It's inspiring to hear from real scientists because you can tell they love what they're doing," says Melinda Barobi, 15, from Parkside Community College in Cambridge. "It's amazing to hear about groundbreaking research as opposed to stuff on the syllabus. This has made me see how important science is; how it is part of everyday life and the foundation of life itself."
For Germina Janzelon, a languages teacher from Henry Mellish School in Nottingham, the practical and academic learning has been a powerful combination for her pupils. "Our school is in quite a deprived area where it is not always cool to be smart. They've learnt from these amazing people that being bright doesn't just involve sitting at a desk it's about discovering a passion, applying your knowledge and then seeing it through. It's so immediate, they can't fail to be interested in it."
Those most affected by global warming have the least control over it. About 5,000 polar bears live in Svalbard, compared with 2,000 people, but their survival is under threat due to thinning ice and pollution. Seeing one standing on the shore in the midnight sun thrills the pupils, some of whom had never been abroad. "It's not like you see one of those every day," says Roshni Valibhai, 15, of Pleckgate High School in Blackburn.
The pupils and crew celebrate as they cross 80 degrees north latitude (the equivalent of crossing the equator in northerly terms) and just one degree further north, Polaris hits ice. Putting on an all-in-one, bright orange survival suit and a rope round his waist, a crew member squeezes into a cage and is lowered by crane on to the pack ice to see if it will withstand his weight. He gingerly steps out and is ordered to jump. He hesitates, then obeys jumping just five inches. The ice holds. Now it is the pupils' turn. Guarded at all times by a gunman, they change into the suits and descend.
"It's incredible, not like a normal science lesson at all," says Tom Channel, 14, from Wildern School in Southampton, as he stands on the seemingly still pack ice, which is, in fact, moving at four knots. To the south, there is water and broken floes; to the north, nothing until the North Pole only 600 miles of ice.
It is an experience that deeply affects everyone. "I'm in a part of the world I'd never even dreamt of visiting and it's just spectacular," says Claire Stopard, a drama teacher accompanying her pupils from Riverleen School in Nottingham. "I'm going to look at my life in a different way from now on because I've understood the impact it can have here in the Arctic, and eventually on the rest of the world. I can't ignore it any longer. When I go back to school I'll have to find a way of communicating that to the pupils."
How they won, by gum
Pupils at Parkside Community College in Cambridge invented biodegradable chewing gum. The four-man team called A New Shade of Green came up with the idea after researching landfills and rubbish bins.
"Because chewing gum is made from crude oil, it takes 250 gallons of water an hour to steam clean it off the streets," says Anna Harley, 14. "It took 16 weeks to get it all off Oxford Street in London and it was back in six weeks. We thought it was mad to use valuable fossil fuels on something as trivial as chewing gum when there are alternatives."
Their gum is made of beeswax and pine resin. A patent is pending, and the Year 10 team is working with a food technologist to make it tastier. The pellets are stored in a cardboard packet with a discarded gum section, but if it is dropped on the street it will not chemically bind to tarmac as commercial gum does and will biodegrade.
"It may seem like a small problem but there is so much gum around," says Anna. "If we can sort out the smaller problems, it will have a big impact on the bigger picture."