A polar bear walks along the edge of 'the ice bridge' in the Robeson channel, near the border between Greenland and Canada.
A pair of red-hulled icebreakers - one Canadian, one American - will batter their way north into uncharted, ice-infested waters next week, seeking to buttress claims to the vast undersea riches at the top of the world.
"We're headed into the Beaufort Sea, as far north as the ice allows," said Jacob Verhoef, the National Resources Canada scientist spearheading Ottawa's effort to map, and eventually claim, a vast swath of the Arctic.
Data gathered by both ships will be shared, but there's no guarantee that the two countries won't eventually be at loggerheads with overlapping claims.
"This really is uncharted territory - we have better maps of the moon," said Captain Steve Barnum, the U.S. chief hydrographer.
The joint expedition, the second in two summers, by the Canadian Coast Guard's best but aging icebreaker, Louis St. Laurent, and the more modern and powerful U.S. coast guard icebreaker, Healy, will map the underwater extension of North America, the continental shelf.
For both countries - as for the other polar-basin states including Russia, Denmark and Norway - defining and mapping the continental shelf underpins rival claims to the Arctic.
Decades of unfulfilled promises by both governments have left Canada and the United States strapped for even modestly capable icebreakers, so this summer's joint two-ship expedition reflects a practical reality as much as a spirit of co-operation.
The two icebreakers can work in tandem, one breaking a path for the other, and can extricate each other if one gets beset. "It was clear that to go further north would require a second ship," Mr. Verhoef said in Tuesday's joint news conference.
Neither country has even a single polar-class icebreaker, unlike the nuclear-powered fleet of Russian vessels that are capable of slicing a path to the North Pole. Other Russian icebreakers, on charter, routinely carry tourists through the Northwest Passage claimed by Canada.
In the thinning summer ice, the Canadian and American ships will take turns clearing a path on the month-long mapping expedition. The Healy will map the seafloor, while the Louis St. Laurent will tow seismic gear that measures sediment depth, which will be critical when both countries file claims under the United Nations Convention on the Law of the Sea.
The U.S. has yet to sign the convention, but Maggie Hayes, the senior State Department official who chairs the multi-agency effort building a U.S. Arctic claim, said she hoped the long-delayed signing might come this year.
Although Canada and the U.S. have embraced a three-year joint effort to send the pair of icebreakers north to gather and share data, Washington remains unimpressed by Canada's sometimes far-reaching and tenuous claims.
Ms. Hayes said she was "skeptical" about Canada's continuing issuance of maps that claim a pie-shaped wedge extending to the North Pole, the so-called sector principle. "I'm being polite," she added, when it was suggested that Washington's long-standing position had been to flatly reject Canada's sector claim, just as it dismisses Ottawa's argument that the Northwest Passage is an internal waterway rather than an international strait.
While scientific and geographic surveys from the current voyage will be shared, Ms. Hayes confirmed that the reams of undersea mapping data collected by U.S. nuclear submarines, which prowled under the Arctic ice for decades during the Cold War, won't be made available to Canada as it prepares its Arctic claim.
Meanwhile, the two icebreakers won't start their joint survey until they are at least 200 nautical miles (370 kilometres) from the coast. Within that zone, the two countries already dispute a long, triangular-shaped area: Canada claims that the international boundary runs due north out into the sea along the 141st west meridian, while Washington contends that the maritime boundary should extend equidistant from the coast.
"The dispute exists, but it is well managed, and we are focusing our effort on co-operation," said Caterina Ventura, Canada's Foreign Affairs acting director of the oceans and environmental law division.
Officials of both countries were keen to avoid discussing the existing bilateral maritime disputes.
The current effort is aimed at determining "where is the edge of the continental shelf off Alaska," Ms. Hayes said.
"We have never had a request [from Canada]for that data."
As global warming shrinks the summer ice cover, exposing shipping lanes and hitherto undrilled oil and gas reserves, the race to stake claims at the top of the world has reached a frenzy. Every Arctic nation has a dispute of varying degrees of nastiness and importance with its neighbours.
Tuesday, as Canadian and U.S. scientists and officials stressed their joint scientific effort, they were also comfortably in agreement in dismissing Russia's high-profile claim to the North Pole and a long undersea shelf reaching almost to Canada's most northerly islands.
The planting of the Russian flag on the sea bottom at the North Pole two summers ago was technically impressive, but didn't prove anything, they said.