This photo, taken by a crew member aboard the Canadian Coast Guard icebreaker Louis St. Laurent, shows the Canadian ship sailing beside the U.S. Coast Guard cutter Healy. (Courtesy Kelly Hansen)

Researchers aboard Canadian and American icebreakers are nearing the end of their Arctic survey mission and are reporting some interesting findings, including a possible undersea volcano.

The survey also found an ridge-like underwater mountain that rises about 1.2 kilometres above the sea floor.

The two countries are conducting their second joint mapping expedition to explore largely unknown parts of the Canada Basin, north of the Beaufort Sea, gathering data on the continental shelf to bolster sovereignty claims.

The U.S. Coast Guard cutter Healy and the Canadian Coast Guard icebreaker Louis St. Laurent will return to port in about a week. A similar mission took place last summer.

"Each of the two ships, the Healy and the Louis, has their own equipment in order to accomplish this mission, and by combining it, we get a much more powerful data collection exercise," said Jacob Verhoef, of the Geological Survey of Canada, who is leading the mapping efforts for Natural Resources Canada.

The Louis St. Laurent would break the ice in front of the Healy while the Healy would collect three-dimensional mapping data of the ocean floor, and the American vessel would return the favour when the Louis was taking readings of the thickness of the sediment below the ocean floor.

Verhoef said the ships collected 40 per cent more data than they expected and went more than 200 kilometres farther north than they anticipated. David Mosher, a scientist with Natural Resources on board the Louis, said the ships were able to sail farther north because of successes earlier in the mission, not because of lighter than normal ice cover.

Verhoef said the ships found remarkable features in their survey, including what looks like an undersea volcano buried under kilometres of sediment.

They also found a sea mount, an elongated, undersea mountain with a flat top, about 1,300 kilometres north of Alaska and 550 kilometres west of Ellesmere Island.

"The sea mount is somewhere up around 80 degress north. It's south of what we call the Alpha Ridge. The volcano is quite a bit south and a bit west of that," said Mosher.

"What also makes it remarkable is that on this planet there still are features like a sea mount that has not been seen before that we have discovered," said Verhoef.

Because this is previously unexplored area, though, the geologists don't know if it contains any significant natural resources.

Both countries are trying to prove their continental shelves extend beyond their existing 200-nautical-mile economic zones, under the United Nations Convention on the Law of the Sea. At stake are areas rich in resources, such as oil and gas, which both countries hope to claim.

"In the area of the Canada Basin, there is a significant amount of sediment. [This] is one of the scientific criteria by which we can define the outer limits of the continental shelf. The data collection will probably help us a lot in defining that outer limit," said Verhoef.

Canada signed on to the international treaty in 2003. The U.S. has not yet ratified the UN treaty, but it is moving ahead with its scientific work anyway.

Arctic experts have said the U.S. and Canada will likely have some overlapping claims on the seabed in the Canada Basin, resulting in disputes.

The two icebreakers did not venture into areas of the Canada Basin where Russia is also making claims, nor did it go into a disputed boundary area farther south between the Yukon and Alaska.

A third joint mapping mission is planned for next summer.