Only in the middle of summer, only on an icebreaker and only thanks to climate change. Our correspondent Margot Minjon is sailing with the Louis St Laurent through the Northwest Passage across the North Pole. The Canadian icebreaker is carrying scientists to carry out research into the rise in global temperatures. Isolated outposts will receive supplies and the ship will be on the look out for unidentified submarines. Part three of a series in which Margot Minjon relates her experiences at the top of the world.
 
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"Finally, last night the Louis St Laurent raised anchor. The captain has decided to take the route through the Peel Sound, between Prince of Wales Island and Somerset Island. The ice is still too thick in all the other passages. The first leg, up to the entrance to the Peel Sound, is still relatively free of ice. Calmly we sail through a layer of grey lumps. Here and there small icebergs float with hardly two metres emerging above the water. Time for a safety drill.
 
About 11 o'clock there are calls that a polar bear can be seen to starboard. Everyone runs out on deck. We've reached the edge of the real ice. On a small white ice floe we can see a large male polar bear pacing up and down. Slowly the Louis St Laurent begins to plough through the ice. The bear is not afraid; he keeps pacing backwards and forwards and makes no attempt to flee.
 
He looks as if he is stranded on the small floe but he is not. Nonchalantly he walks across to another "floe", his paws hardly disappearing beneath the water. There's a solid sheet of ice just under the surface. The Louis St Laurent forces its way through with cracking noises and shudders.
 
A few hundred metres further along on the same side we can see a female polar bear with two cubs. They're not afraid either; they hardly even look at the ship. In the ice there are holes used by seals for breathing. The female keeps a close watch on a couple of the holes. Polar bears are left-handed, one of the crew tells me. Just watch, in a while the female will pull a fat seal up out of the hole with her left paw.
 
It doesn't happen while we're looking. It's unusual, the crewman adds, for a male bear to be so close. If he gets hungry he's quite likely to eat one of the cubs.
 
Two metre ice
We go back inside. The ship is now shaking so badly that we have to grab hold of the rails in the gangways.

The icemaster holds a talk. André Pellard has an important function on the ship: using all kinds of information, it's his job to predict the thickness of the ice. On this basis a route can be charted. If his information is insufficient, he flies ahead in a helicopter to take a look for himself.
 
The further we travel, the thicker the ice will get, he says. Here it's up to one metre thick but that will probably increase to two metres. The wind and the current have pushed up a lot of ice in the Peel Sound. In the other routes it's even thicker.
 
Climate change has resulted in the ice melting but, paradoxically, there is now more ice in the Northwest Passage. Huge floes are drifting into the Passage and then freezing up again.
 
Special guests
It's 31 July and the Louis St Laurent is the first ship to go through the Passage this year - albeit with difficulty. Tomorrow I'm going to ask the captain whether he thinks any other ships will make it through this summer.
 
Since the Louis St Laurent is going thorough the Passage for the third year in a row, and only does so once a year, there are a number of special guests on board. The Canadian deputy foreign minister, a senator and a number of prominent scientists. PowerPoint presentations and brainstorming sessions are held three times a day in a separate room. Are the climate prediction models accurate enough? Do we have enough information?
 
At eight o'clock in the morning we see our seventh polar bear."
 

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Part Four
On Monday morning we were stuck in the ice. The captain brought the ship to a halt last night to give everyone some rest. It's difficult to sleep on board and icebreaker: the ship throbs and lurches back and forth and up and down. You can hear and feel the ice floes hitting the hull and the engines make an enormous amount of noise.

Although it's light here 24 hours a day, it did freeze last night. At six o'clock the ship was stuck. No need for panic, though: the captain turns on the bubble system. Compressed air blows away the fresh ice from around the hull and the Louis St Laurent can then manoeuvre its way loose.

Ingeneous
Icebreaking itself is quite ingenious. The bow slides up onto the ice, which then breaks under the weight of the ship. This process is helped by a large steel blade attached to the keel. The system works best with full fuel tanks, according to Captain Andrew McNeill. If they're depleted the ship weighs less. The engines then need more fuel to get through the ice and the tanks empty faster.

And that's really fast. In heavy ice, the Louis St Laurent consumes 1.9 litres for every 30 centimetres. The ship is 120 metres in length, 24 metres across and has a capacity of 25,000 horsepower. It has a crew of 45.

The ice today is around one metre thick, three metres in some places. We're standing on the bridge looking around us. It's a sunny day. There's ice everywhere, everywhere the eye can see.

The first
This year we're the first ship to travel the Northwest Passage. From the other end a Russian icebreaker is on its way carrying paying passengers. In September two freighters will travel from East to West, plus a couple of Coastguard vessels. No more than eight ships altogether.

Newspapers have been reporting that the Northwest Passage was free in 2007 and 2008 but that doesn't really mean free and open. There are five routes making up the Northwest Passage. This time the Louis St Laurent has taken the Peel Sound because it has the least ice at present. But there are still big chunks of perennial ice floating around. "If the wind blows, it gets blown together and you end up completely trapped," says Captain McNeill.

So is there less ice than in 2007 and 2008? "In fact, yes," says McNeill. "But it doesn't mean much, since we're later than we were last year. There's less ice than I expected, but there are parts with more ice."