During a trip late last month to Canada's Far North, Mr. Harper criticized Russia in an interview with The Wall Street Journal, portraying its strategy in the region as aggressive and "a disappointment." But he said Russia's actions—including alleged incursions into Canada's Arctic airspace, which Moscow denies—strengthen Ottawa's commitment to the region.

Those actions "remind us, as I say, that we have an obligation as a sovereign nation to have an ability on land, sea and air to be present and to assert that presence at all times," Mr. Harper said.

Aside from its show of military might, Ottawa and some of Canada's semiautonomous provinces also have launched a series of diplomatic and economic efforts to put a Canadian stamp on a larger swath of the Arctic—a bid to counter Russia's own efforts to bolster its claims in the region.

A handful of other nations, including the U.S. and Denmark, also claim some of the Arctic—an ice-choked ocean ringed by archipelagos of treeless tundra—and also are racing to assert territorial rights over contested borders.

Now, economic activity is limited to small-scale mining and oil exploration, native fishing and hunting. But with increasing ice melt, which many scientists and governments ascribe to global warming, that activity is expected to increase sharply.

Canada signed on to a United Nations treaty in 2003 that triggered a 10-year timeline for submitting claims over waters outside its sovereign territory. With that deadline looming, Canadian scientists hope to finish this month field work aimed at extending Canada's rights over about 656,000 square miles of ocean—an extension of its 200-mile economic-exclusion zone.

That claim would allow Canada to regulate most economic activity carried out in those waters: from rule making over fishing, shipping and oil and minerals exploration to taking responsibility over oil spills and rescues.

Here in Resolute—a community of about 250 native Inuit well above the Arctic Circle in Canada's northernmost Nunavut province—Canadian officials are preparing to shoulder that responsibility.

Part of the recent military training here was a simulated response to a commercial air emergency. Earlier this year, a group of Arctic powers divvied up search-and-rescue responsibilities over the region.

The 1,100 Canadian personnel on hand for the exercise—including investigators from Canada's air-safety regulator—ended up carrying out real-world search-and-rescue operations after a chartered Boeing 737 crashed during the exercise, just outside Resolute's airport, killing 12.

"We have to be able to protect [the Canadian Arctic], defend it, rescue people, respond to disasters, have effective regulatory systems for development," Mr. Harper said, a day after visiting Resolute to address troops. "These require investments and a range of capabilities over a long period of time," he said. "And that's what we are doing."

The effort comes as Arctic exploration increasingly becomes a reality. Last month, Exxon Mobil Corp. and OAO Rosneft agreed to jointly explore for oil in the Russian Arctic. Royal Dutch ShellPLC, meanwhile, is inching closer to regulatory approval to drill in Arctic waters offshore Alaska.

Canada also is investing $100 million to map promising geological formations in its northern territories, in an effort to lure private investment. It shares that data, free of charge, with interested oil and mining companies.

Canada's U.N. claim over the Arctic hinges in large part on how far its continental shelf extends. That is the subject of seabed-data collection now being conducted by U.S. and Canadian icebreaking ships sailing near the North Pole. The countries teamed up to share the costs of the costly and unpredictable venture.

A flashpoint between Canadian and Russian officials is the Lomonosov Ridge, an 1,100-mile undersea ridge that runs under the North Pole from Greenland to Russia.

"They are claiming it as a natural prolongation, or extension, of their continent, and we are claiming it as a natural prolongation of our continent," said Jacob Verhoef, a senior scientist at the Geological Survey of Canada with responsibility for the U.N. claim.

The province of Quebec has embarked on a 25-year effort to lure about $80 billion in new investment in its far north. This year it said it had already won commitments of about $8.2 billion for 11 new mining projects there.

Canadian companies, meanwhile, are slowly building up experience operating in the harsh Arctic environment. Toronto-based Agnico-Eagle Mines Ltd. started gold production at its Meadowbank mine—located near Baker Lake, in Nunavut, and just south of the Arctic Circle—just about three years ago. Costs are higher than executives estimated, but the mine—bolstered by high gold prices—singlehandedly lifted Nunavut's economy by almost 12%, says an independent study.

"It's the skill set that matters in this environment," said Agnico-Eagle's CEO, Sean Boyd, who is now pushing ahead with development of another gold mine in Nunavut. "And these skill sets are improving."

*Chip Cummins at chip.cummins@wsj.com