* Military activity stepping up as Arctic thaws
* Disputes stir over oil and gas access, shipping
* Potential thaw opens technology opportunities
By Alister Doyle, Environment Correspondent
OSLO, June 22 Arctic nations are promising to avoid new "Cold War" scrambles linked to climate change, but military activity is stirring in a polar region where a thaw may allow oil and gas exploration or new shipping routes.
The six nations around the Arctic Ocean are promising to cooperate on challenges such as overseeing possible new fishing grounds or shipping routes in an area that has been too remote, cold and dark to be of interest throughout recorded history.
But global warming is spurring long-irrelevant disputes, such as a Russian-Danish standoff over who owns the seabed under the North Pole or how far Canada controls the Northwest Passage that the United States calls an international waterway.
"It will be a new ocean in a critical strategic area," said Lee Willett, head of the Marine Studies Programme at the Royal United Services Institute for Defence and Security Studies in London, predicting wide competition in the Arctic area.
"The main way to project influence and safeguard interests there will be use of naval forces," he said. Ground forces would have little to defend around remote coastlines backed by hundreds of km (miles) of tundra.
Many leading climate experts now say the Arctic Ocean could be ice-free by 2050 in summer, perhaps even earlier, after ice shrank to a record low in September 2007 amid a warming blamed by the U.N. Climate Panel on human burning of fossil fuels.
Previous forecasts had been that it would be ice-free in summers towards the end of the century.
Among signs of military concern, a Kremlin document on security in mid-May said Russia may face wars on its borders in the near future because of control over energy resources -- from the Middle East to the Arctic.
Russia, which is reasserting itself after the collapse of the Soviet Union, sent a nuclear submarine in 2008 across the Arctic under the ice to the Pacific.The new class of Russian submarine is called the Borei -- "Arctic Wind".
Canada runs a military exercise, Nanook, every year to reinforce sovereignty over its northern territories. Russia faces five NATO members -- the United States, Canada, Norway, Iceland and Denmark via Greenland -- in the Arctic.
In February, Canadian Prime Minister Stephen Harper criticised Russia's "increasingly aggressive" actions after a bomber flew close to Canada before a visit by U.S. President Barack Obama.
And last year Norway's government decided to buy 48 Lockheed Martin F-35 jets at a cost of 18 billion crowns ($2.81 billion), rating them better than rival Swedish Saab's Gripen at tasks such as surveillance of the vast Arctic north.
Much may be at stake. The U.S. Geological Survey estimated last year that the Arctic holds 90 billion barrels of undiscovered oil -- enough to supply current world demand for three years.
And Arctic shipping routes could be short-cuts between the Pacific and Atlantic Oceans in summer even though uncertainties over factors such as icebergs, insurance costs or a need for hardened hulls are likely to put off many companies.
Other experts say nations can easily get along in the North.
"The Arctic area would be of interest in 50 or 100 years -- not now," said Lars Kullerud, President of the University of the Arctic. "It's hype to talk of a Cold War."
He said an area in dispute between Russia and Denmark at the North Pole was no bigger than a "grey zone" in the Barents Sea over which Russia and Norway have been at odds for decades and where seismic surveys indicate gas deposits in shallow waters. "The talk of a new Cold War is exaggerated," said Jakub Godzimirski, of the Norwegian Institute of International Affairs. "We have seen a lot of shipping traffic going all over the world without tensions," he said.
Governments also insist a thaw does not herald tensions.
"We will seek cooperative strategies," U.S. Deputy Secretary of State Jim Steinberg told Reuters during a meeting of Arctic Council foreign ministers in Tromsoe, Norway.
"We are not planning any increase in our armed forces in the Arctic," Russian Foreign Minister Sergei Lavrov said at the talks in late April, also stressing cooperation.
"Everyone can make easy predictions that when there are resources and there is a need for resources there will be conflict and scramble," Norwegian Foreign Minister Jonas Stoere said. "It need not be that way."
Agreeing with them that Cold War talk is overdone, Niklas Granholm of the Swedish Defence Research Agency nonetheless said: "The indications we have is that there will be an increased militarisation of the Arctic."
That would bring security spinoffs. Many may be humdrum -- ensuring safety of shipping, or deployment of gear in case of oil spills such as the 1989 Exxon Valdez accident in Alaska.
Wider possibilities include a possible race between Russia and the United States for quieter nuclear submarines.
Submarines, which can launch long-range nuclear missiles, have long had a hideout under the fringe of the Arctic ice pack where constant waves and grinding of ice masks engine noise.
"It might lead to a new generation of ultra-silent submarines or other, new technologies," said Granholm.
Greater access to Arctic resources and shipping is one of few positive spinoffs as climate change undermines the hunting cultures of indigenous peoples and threatens wildlife from caribou to polar bears.
The Northwest Passage past Canada, for instance, cuts the distance between Europe and the Far East to 7,900 nautical miles (14,630 km) from 12,600 via the Panama Canal. Similar savings can be made on a route north of Russia.
A U.N. deadline for coastal states to submit claims to offshore continental shelves passed on May 13 and in 2007 Russia planted a flag on the seabed in 13,980 feet (4,261 metres) of water under the Pole to back its claim.
Russia's flag-planting stunt might also herald new technologies -- the world record for drilling in water depth is 10,011 feet (3,051 metres), held by Transocean Inc, the world's largest offshore drilling contractor.
Claims by Norway and Iceland do not extend so far north and Denmark, Canada and the United States were not bound by the deadline.
-- For Reuters latest environment blogs click on: blogs.reuters.com/environment/ (Editing by Sara Ledwith)