Canada's latest bid to assert its claim to the Arctic fell just short of its mark this week when open water forced a fleet of snowmobiles to turn back before reaching its goal of the magnetic North Pole.

Organizers, however, consider the $750,000, 1,600-kilometre round-trip trek a successful display of national sovereignty. "They could have gone further, but then it might have become a search and rescue," said Peter Moon, an organizer of the expedition by the Canadian Ranger Patrol.

Moon and 29 other Rangers from the Yukon, Northwest Territories and Nunavut are now on their way back to expedition's base in Resolute, Nunavut.

Open water in the High Arctic is not unusual, even in April. But what happened this week does serve as a reminder of the challenges that climate change has brought to Canada's claim to the region.

The United States and Europe do not recognize Canada's sovereignty over Arctic waters, and the Northwest Passage in particular. Until now, the debate has been academic, but interest is growing as the region warms and the ice thins.

A recently declassified report from the U.S navy's Office of Naval Research calls for increased resources in the Canadian Arctic in response to the increase in commercial and military traffic through the passage expected to result from climate change. "Scientific models consistently suggest that seasonal sea lanes through the formerly ice-locked Arctic may appear as soon as 2015," says the report.

Ottawa's position is that "Canada's sovereignty over internal waters would be undiminished should the extent of ice-covered waters be reduced in size," says Reynald Doiron of the Department of Foreign Affairs.

The main point of the Ranger Patrol's Operation Kigliqaqvik, after the Inuktitut word for "the place at the edge of known land," is to reassert Canada's claim to those waters.

The expedition reached 79 degrees north latitude, a point about 70 kilometres shy of magnetic north, at about 5 p.m. on Tuesday. Because the pole wanders by dozens of kilometres on a daily basis, expedition leaders can claim they reached the general vicinity of the pole, if not the precise location.

The group spent the next couple of days near an abandoned U.S. air force weather station on Ellef Ringes Island, celebrating the Ranger Patrol's 60th anniversary. The patrol, made up primarily of northern aboriginal hunters trained by the Armed Forces, is Canada's eyes and ears in the vast Arctic wilderness and was created to bolster the country's sovereignty in the region.

But the Canadian Forces aren't content to rely on the occasional snowmobile patrol. Planners at the Department of National Defence are interested in using more sophisticated technology to help keep watch on the Arctic.

Tests of new "over-the-horizon" monitors are planned for next year on the east coast of Baffin Island, said Lt.-Col. Rory Kilburn, chief of staff for Canadian Forces Northern Area in Yellowknife. High-frequency surface wave radar under development at the Defence Research Establishment in Ottawa is designed to spot ships hundreds of kilometres away.

Also on DND's northern wish list are underwater acoustic monitors, a new ship-tracking satellite and robotic surveillance airplanes. But Kilburn admitted it won't be easy to find the money for such multimillion-dollar projects.