YOKOSUKA, Japan (AP) — To the world's military leaders, the debate over climate change is long over. They are preparing for a new kind of Cold War in the Arctic, anticipating that rising temperatures there will open up a treasure trove of resources, long-dreamed-of sea lanes and a slew of potential conflicts.

By Arctic standards, the region is already buzzing with military activity, and experts believe that will increase significantly in the years ahead.

Last month, Norway wrapped up one of the largest Arctic maneuvers ever — Exercise Cold Response — with 16,300 troops from 14 countries training on the ice for everything from high intensity warfare to terror threats. Attesting to the harsh conditions, five Norwegian troops were killed when their C-130 Hercules aircraft crashed near the summit of Kebnekaise, Sweden's highest mountain.

The U.S., Canada and Denmark held major exercises two months ago, and in an unprecedented move, the military chiefs of the eight main Arctic powers — Canada, the U.S., Russia, Iceland, Denmark, Sweden, Norway and Finland — gathered at a Canadian military base last week to specifically discuss regional security issues.

None of this means a shooting war is likely at the North Pole any time soon. But as the number of workers and ships increases in the High North to exploit oil and gas reserves, so will the need for policing, border patrols and — if push comes to shove — military muscle to enforce rival claims.

The U.S. Geological Survey estimates that 13 percent of the world's undiscovered oil and 30 percent of its untapped natural gas is in the Arctic. Shipping lanes could be regularly open across the Arctic by 2030 as rising temperatures continue to melt the sea ice, according to a National Research Council analysis commissioned by the U.S. Navy last year.

What countries should do about climate change remains a heated political debate. But that has not stopped north-looking militaries from moving ahead with strategies that assume current trends will continue.

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Russia, Canada and the United States have the biggest stakes in the Arctic. With its military budget stretched thin by Iraq, Afghanistan and more pressing issues elsewhere, the United States has been something of a reluctant northern power, though its nuclear-powered submarine fleet, which can navigate for months underwater and below the ice cap, remains second to none.

Russia — one-third of which lies within the Arctic Circle — has been the most aggressive in establishing itself as the emerging region's superpower.

Rob Huebert, an associate political science professor at the University of Calgary in Canada, said Russia has recovered enough from its economic troubles of the 1990s to significantly rebuild its Arctic military capabilities, which were a key to the overall Cold War strategy of the Soviet Union, and has increased its bomber patrols and submarine activity.

He said that has in turn led other Arctic countries — Norway, Denmark and Canada — to resume regional military exercises that they had abandoned or cut back on after the Soviet collapse. Even non-Arctic nations such as France have expressed interest in deploying their militaries to the Arctic.

"We have an entire ocean region that had previously been closed to the world now opening up," Huebert said. "There are numerous factors now coming together that are mutually reinforcing themselves, causing a buildup of military capabilities in the region. This is only going to increase as time goes on."

Noting that the Arctic is warming twice as fast as the rest of the globe, the U.S. Navy in 2009 announced a beefed-up Arctic Roadmap by its own task force on climate change that called for a three-stage strategy to increase readiness, build cooperative relations with Arctic nations and identify areas of potential conflict.

"We want to maintain our edge up there," said Cmdr. Ian Johnson, the captain of the USS Connecticut, which is one of the U.S. Navy's most Arctic-capable nuclear submarines and was deployed to the North Pole last year. "Our interest in the Arctic has never really waned. It remains very important."

But the U.S. remains ill-equipped for large-scale Arctic missions, according to a simulation conducted by the U.S. Naval War College. A summary released last month found the Navy is "inadequately prepared to conduct sustained maritime operations in the Arctic" because it lacks ships able to operate in or near Arctic ice, support facilities and adequate communications.

"The findings indicate the Navy is entering a new realm in the Arctic," said Walter Berbrick, a War College professor who participated in the simulation. "Instead of other nations relying on the U.S. Navy for capabilities and resources, sustained operations in the Arctic region will require the Navy to rely on other nations for capabilities and resources."

He added that although the U.S. nuclear submarine fleet is a major asset, the Navy has severe gaps elsewhere — it doesn't have any icebreakers, for example. The only one in operation belongs to the Coast Guard. The U.S. is currently mulling whether to add more icebreakers.

Acknowledging the need to keep apace in the Arctic, the United States is pouring funds into figuring out what climate change will bring, and has been working closely with the scientific community to calibrate its response.

"The Navy seems to be very on board regarding the reality of climate change and the especially large changes we are seeing in the Arctic," said Mark C. Serreze, director of the National Snow and Ice Data Center at the Cooperative Institute for Research in Environmental Sciences University of Colorado. "There is already considerable collaboration between the Navy and civilian scientists and I see this collaboration growing in the future."

The most immediate challenge may not be war — both military and commercial assets are sparse enough to give all countries elbow room for a while — but whether militaries can respond to a disaster.

Heather Conley, director of the Europe program at the London-based Center for Strategic and International Studies, said militaries probably will have to rescue their own citizens in the Arctic before any confrontations arise there.

"Catastrophic events, like a cruise ship suddenly sinking or an environmental accident related to the region's oil and gas exploration, would have a profound impact in the Arctic," she said. "The risk is not militarization; it is the lack of capabilities while economic development and human activity dramatically increases that is the real risk."