"If a polar bear approaches, wave your arms and shout 'Go away polar bear!'" It is not a sophisticated line of defence: in the Arctic you'd usually carry weapons in case of attack. But we are planning an expedition in a conservation area, where they are illegal. "Actually," the park ranger adds, "it's not the bears which will kill you. It's the cold."
I am on Baffin Island, a splodge of desolation on the map of the Canadian Arctic – and the fifth-largest island in the world (after Greenland, New Guinea, Borneo and Madagascar).
Arctic Canada has the draw of the wilderness. Auyuittuq National Park is a glorious space of glacier-draped peaks and snow geese. A group of friends who skied to the South Pole chose the Akshayuk Pass – a 100km north-south traverse through the park – as their next expedition; it is not the obvious choice for a first trek, but I decided to join them.
Our hike skirts past Mount Thor, the tallest cliff in the world, with a 1,250m vertical drop, and Mount Asgard, the flat-topped peak from which James Bond leapt with a Union flag parachute in A Spy Who Loved Me. The route follows the valley along the edge of the Penny Ice Cap – a remnant of the Laurentide Ice Sheet, and an environment in jeopardy. According to scientists from the University of Boulder, ice caps on the northern plateau of Baffin Island in the Canadian Arctic have shrunk by more than 50 per cent in the last half century, and are expected to disappear by the middle of the century.
Our expedition is unaided, so we must carry 13 days' worth of supplies. In the weeks before, I run with weights to build up strength. I source merino inner layers and pants (the wool is light, quick-drying, and doesn't smell). And I import dehydrated meals from Norway. I also practise putting up my tent, ready to do it in winds gusting up to 70km/h in a rain or snow storm. Once we share out stoves, fuel, satellite phones and first aid, my pack weighs 30kg – the same as a fully grown sheep.
I have first-day-of-school nerves during the safety briefing, which takes place in a hut in the small Inuit settlement of Qikiqtarjuaq. A walrus-hunting boat ferries us through the taut, blue day to the mouth of the Pass. I shiver in my orange survival suit as we pass huge icebergs, groaning as they melt and wrench apart, and broad oceanic fjords. The other four chat and share a tube of Pringles (price US$12/£7.80 from the Qikiqtarjuaq co-op store). Billy the Boatman points out places where the ice used to be. "We have watched it disappear," he says. "This has always been our land, the place my family would bring dogs to hunt. That way of life is gone."
We reach the shore in the evening, where we fasten our gaiters, sling on our packs, and take out our trekking poles. Yellow granite cliffs rise either side of us, streaked with black lichen and broken up by hanging valleys with white water spilling over them. Ice is smeared over the higher peaks. We hike over marshy tundra, tufted with grass and Arctic cotton, for 5km before setting up the tents. Our camp rituals emerge: wrestling the pump on the water filter, whose instructions we threw away to save weight; digging a latrine – you burn the paper and bury the rest; boiling water, then burning your tongue on the scalding tea...
The permafrost impedes drainage, so we spend the first three days walking through sand and bogs. Then we are stopped by the sluicing water running down from the Rundle Glacier above us. It is a fierce torrent, with boulders spinning in the rapids. Doug, the most experienced in our group, strips down to shorts and Neoprene boots to test the depth. After 30 minutes he confirms it is too dangerous to try to cross it so late in the day: five years ago an experienced Californian trekker died during a similar attempt.
As there is still some warmth in the sun – a bit like a cool day in Scotland – we balance on the sharp, wet rocks, and wash ourselves in the semi-frozen water. The midges target any inch of exposed flesh. Maryn, the other woman on the trip, has recently been to Botswana. "These make the African mosquitoes look like aphids," she reflects, rubbing an egg-size bite.
The 24-hour sun is at its coolest in the early hours, so we wake at 2.30am when there should be less melt. The water level is hardly changed, so we retrace our steps through the mist to a point where the river is braided and shallower. The water is still thigh deep, and my skin turns spanked crimson. I walk downstream from Doug, letting him break the brunt of the flow. Still I work hard to stop my legs being pulled from under me.
The terrain on the western side of the river is alien: grey scree and unstable fields of rocks heaped on rocks. Imagine climbing a flight of steps where each tread is jagged, waist-high, and not necessarily nailed down. I make the mistake of trying to use my hands for balance, but tip my weight too far forward and am pinned underneath my rucksack. The trick is to keep momentum by planning your next three foot holds, and never pausing to look down. There is an element of faith, a bit like skiing. It is almost a meditation.
On the day we cross the Rundle, when we stop for lunch the sun is pleasant. We stretch out and relax, admiring the light catching the colours in the cliffs. Purple dwarf fireweed grows through the grass. As we eat cheese and crackers, an Arctic fox with brown summer fur stalks round us. He is beautiful, delicately placing his paws. We fill our bottles in a stream edged with Arctic poppies, the sweet water singing down the hill.
Later that afternoon we cross the Turner Glacier, under the stubby summit of Asgard. It is not the glacier mint prism I'd pictured, but a slick of dirty ice with a honeycomb surface. Some distance before the edge, Doug leads us to the foot of the glacier. We look back to see the crevasse we just avoided.
On the seventh night the temperature drops. We camp in dense fog, listening to chunks of debris falling out of the frozen river banks and crashing into the ugly water below. During the night there is a huge cannoning sound, and I look out of the tent to see a massive rockfall on the other side of the river. Puffs of 3.5 billion-year-old Precambrian granite dust hang in the air like smoke.
On the eighth day it begins to drizzle as we pass the limpid green pool of Crater Lake, the jagged peaks reflected in its surface. Jumping across rocks I miss my footing and am soaked to the waist. But the day is clement, so I finish the last stretch of the trek in my long johns.
Climate change is opening up the Arctic. It is still a remote, treacherous place, evoking memories of naval explorers Sir Martin Frobisher and Sir John Franklin. In a sign of the changing times, where Franklin died trying and failing to find the North West Passage – a sea route going past Baffin Island, through the Arctic Ocean – the first commercial vessel navigated it successfully in 2008. To see the Auyuittuq Park as it was, and without other tourists, now is the time to go.
*You can fly to Qikiqtarjuaq on FirstAir from Ottawa (with connections from other cities in southern Canada) for C$1,884 (£1,250) return in June. Together with flights from London to Ottawa, the total air fare is likely to be around £1,700.
*The writer arranged her trek independently. Black Tomato (020-7426 9888; blacktomato.co.uk) can arrange a 12-day trek across the Akshayuk Pass on Baffin Island from £5,599 per person. This includes international flights (starting in London), guides, all equipment and transfers. The best time to do this trek is the end of July.
*Parks Canada, pc.gc.ca