The Canadian Coast Guard icebreaker Louis St. Laurent sails beside the U.S. Coast Guard cutter Healy in 2008 in a photo from a Canadian crew member. (Submitted by Kelly Hansen)

For the first time, ships involved in a Canada-U.S. seabed mapping project will together explore a potentially resource-rich part of the Beaufort Sea claimed by both countries.

The two research vessels have worked together to map the Arctic seabed for three years, but never in the pie-shaped, 21,000-square-kilometre disputed area that is approximately the size of Lake Ontario.

The U.S. says the sea border should go out at a 90-degree angle from the land at the Canada-U.S. border, but Canada's opinion is that it should continue to follow the 141st meridian, which is what the land border follows.

The work, to be done from Aug. 2 to Sept. 14, will help define the outer edge of the North American continental shelf, data that will be used by Canada and the U.S. in submissions to the United Nations that will stake new claims to the Arctic seabed.

Both countries are preparing claims under the United National Law of the Sea, though the U.S. has not yet signed the treaty. The treaty allows countries to claim sea floor to the edge of their extended continental shelves, beyond the 380 kilometres from the coastline they currently control.

The claims must be filed by 2013.

"What we're doing right now is determining where is the shelf, what is the extent of any overlap," said Foreign Affairs spokeswoman Alison Saunders.

The U.S. and Canada have been working to resolve the Beaufort dispute, Saunders said. Officials from both governments met in Ottawa last week and will meet again early next year.

"There's an understanding between [Foreign Affairs Minister Lawrence] Cannon and [U.S. Secretary of State Hilary] Clinton to hold a dialogue of government experts on the Beaufort Sea maritime boundary," Saunders said.

The Canadian Coast Guard icebreaker Louis S. St-Laurent and U.S. icebreaker Healy have been working together for two years. They will also do research into ice conditions and ocean acidification.

David Mosher, who will be Canada's chief scientist on the St-Laurent, said he looks forward to making scientific discoveries during the exploration.

"Much is unknown and remains unknown about the Arctic, even about how the ocean originally formed," Mosher said. "I think it's those fundamental science questions that excite me more than anything.

With files from The Canadian Press