Image copyright Annika Ogilvie, Fednav Image caption In 2014 the Nunavik became the first cargo ship to go through the Northwest Passage without an icebreaking escort ship leading the way

Climate change is increasingly opening up the Northwest Passage, an Arctic sea route north of the Canadian mainland.

Could it herald an era of more cargo shipping around the top of the world?

Back in the 19th Century there was a race to map and navigate the Northwest Passage through the Arctic Ocean as a shortcut between the North Atlantic and North Pacific.

Explorers would take ships up Greenland's west coast, then try to weave through Canada's Arctic islands, before going down the Bering Strait between Alaska and Russia.

The problem was that even in the summer the route was mostly blocked by impenetrable ice. On one of the best-known expeditions - that of the UK's Sir John Franklin in 1845 - all 129 crew members perished after their two vessels got stuck.

Today, more than 170 years later, a warming Arctic means that the route is increasingly accessible for a few months each summer.

And according to some estimates, Arctic ice is retreating to the extent that the Northwest Passage could become an economically viable shipping route.

For shipping firms transporting goods from China or Japan to Europe or the east coast of the US, the passage would cut thousands of miles off journeys that currently go via the Panama or Suez canals.

The Canadian government is certainly hopeful that this will be the case.

Late last month the country's trade minister Jim Carr said that the route "will in a matter of a generation, probably be available year round".

At the moment it is still a risky business though, with ice remaining a serious problem.

But in 2014 the Nunavik became the first cargo ship to traverse the passage unescorted when it delivered nickel from the Canadian province of Quebec to China.

Image copyright Fathom Marine Image caption The Arctic Ocean is not a place where you want something to go wrong with your vessel

Tim Keane, manager of Arctic operations for the ship's owner, Canadian maritime transport firm Fednav, was on board the Nunavik for the journey.

He says that the trip was pleasantly "boring" - the ship didn't have to spend days struggling through ice.

Instead it did the journey from Quebec to China in 26 days, more than two weeks less than the 41-day return via the Panama Canal.

"From a distance point of view it makes tremendous sense to use the Northwest Passage when it's available to you," he says.

While Fednav doesn't have immediate plans to use the route again, it remains a possibility depending on the cargo's destination, and the time of year.

A year prior to the Nunavik's journey, another large vessel - the Nordic Orion - became the first cargo ship to go through the passage, albeit led by a Canadian coastguard icebreaker.

Owner, Danish company Nordic Bulk Carriers, said afterwards that "we hope and expect to do it" again.

Image copyright AFP Image caption The wider North America Arctic region, including Canada's Nunavut territory (pictured) is very sparsely populated

At the moment the number of ships going through the passage is low, but is rising.

In 2017 a total of 32 vessels made the journey, but only one of those was a cargo ship. The others included adventure yachts, dedicated icebreakers, a cruise ship, and a tanker.

This compares with 18 vessels in total in 2016, and 16 in 2015.

Canadian logistics company Fathom Marine expects shipping levels in the passage to keep growing, led by more mining projects across the region.

President Niels Gram says his company is "quite bullish in terms of providing marine support for projects that are in the area, and investing to support that".

He says that as more mineral mining projects go into production, the raw materials will need to be shipped to world markets, and sites will need to be resupplied.

Image copyright Science Photo Library Image caption Ice, such as this in Lancaster Sound, Nunavut, remains a serious risk for shipping in the Northwest Passage

However, some Arctic experts are not convinced that the Northwest Passage will ever be a busy commercial trade route.

Malte Humpert, the founder of The Arctic Institute think-tank, is among them.

He says the passage is a "less clear cut" option for shipping than the Northern Sea Route, which runs along the Russian Arctic coast between Asia and Europe.

He points out that the Northwest Passage has several geographic disadvantages, including the many islands that keep the region more clogged with ice than the Russian route.

Other challenges for the Canadian route is a lack of deep water ports and limited search and rescue capabilities.

There's also the continuing disagreement over access to the passage. Canada claims sovereignty, while the US and others consider the passage to be international.

Image copyright Getty Images Image caption All members of Sir John Franklin's 1845 expedition perished, and were depicted in a number of paintings

And when it comes to levels of investment and development, the wider North American Arctic region of Alaska, Canada's northern territories and Greenland is now trailing behind the Russian Arctic.

Russia is trying to boost its northern economy, with plans to invest millions of dollars over the next few years to build nuclear-powered ice-breakers and develop port infrastructure along the Northern Sea Route.

Canada is however planning to redevelop its one deep-water port with access to the Arctic - Churchill on Hudson Bay, in the province of Manitoba.

International Trade Minister Mr Carr says the work will open up "an entirely different world" for Canada's northern regions.

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Jessica Shadian is director of Arctic 360, an organisation that promotes the North American Arctic and the geopolitical importance of sustainably investing there.

She sees its economic potential as vast, but says Canada is "being slow to recognise its own north and the potential that it has".

Instead Ms Shadian adds that China is more closely looking at developing the North American Arctic as part of an ambitious scheme to transform its connections to Europe and beyond.

She wants Canadians and Americans to focus more on the economic returns the region can bring.

"When you start thinking about the North American Arctic as an emerging economy, it engenders a whole different mindset among investors," she says.