RESOLUTE BAY, Canada - For 500 years, explorers nudged their ships through these Arctic waters, vainly seeking a shortcut to the riches of the East. The Northwest Passage, a deadly maze of sea ice, narrow straits and misshapen islands, still holds the traces of those who failed.

There are feeble cairns, skeletons lying face down where explorers fell, makeshift camps piled high with cannibalized bones and, on one rocky spit, a trio of wind-scoured tombstones. Whole expeditions, hundreds of men and entire ships, are missing to this day. The first explorer to survive a crossing, in 1906, spent several winters trapped by ice.

Despite that - or maybe because of it - Canadian Mountie Ken Burton wanted nothing more than to join the pantheon of polar explorers who had threaded their ships through the passage's narrow ice leads and around its shimmering blue-green icebergs.

In the summer of 2000, Burton gingerly nosed a 66-foot aluminum patrol boat into the heart of the Northwest Passage. Ice floes could crumple the boat like paper. Even the smallest iceberg, a growler, could rip apart its delicate hull.

But there were no bergs. No growlers. No thin cakes of pancake ice. To his surprise, Burton found no ice at all. A mere 900 miles south of the North Pole, where previous explorers had faced sheets of punishing pack ice, desperation and finally death, Burton cruised past emerald lagoons and long sandy beaches. Crew members stripped and went swimming.

Burton whipped through the passage, "not hurrying," in a mere 21 days.

"We should not, by any measure, have been able to drive an aluminum boat through the Arctic," said Burton, still astonished and just slightly disappointed. "It was surreal."

It was also a glimpse of the future. For several summers now, vast stretches of the Northwest Passage have been free of ice, open to uneventful crossings by the flimsiest of boats. Climate experts now blandly predict what once was unimaginable: In 50 years or less, the passage will be free of ice throughout the summer, a prospect that could transform the region and attract a flotilla of cruise ships, oil supertankers and even U.S. warships.

"It's something no one would have dreamed up for our lifetime," said Lawson Brigham, deputy director of the U.S. Arctic Research Commission and former captain of the U.S. Coast Guard icebreaker Polar Sea, which made it through the passage in 1994.

The parting of the ice is the product of natural, long-term atmospheric patterns that have warmed the Arctic in recent decades and, to a lesser extent, the gradual heating of the planet by greenhouse gases.

The planet's temperature has risen 1 degree Fahrenheit over the last century. In the Arctic, temperatures have risen 3 to 4 degrees. In these northern seas, at the boundary between water and ice, that small difference has changed the landscape for thousands of miles.

"The image of the Arctic was always one of an ice-locked, forbidden spot," said James Delgado, director of the Vancouver Maritime Museum and author of Across the Top of the World: The Quest for the Northwest Passage. "If we as a species have wrought this change, it's humbling, given its history as such a terror-filled place."

The receding ice is throwing open a gateway to Far North, a region long defined by its isolation, sparse population and stark, simple beauty. Ship traffic could carry with it a rush of civilization and commerce.

"It's not just about transport; it's about the whole development of the Arctic frontier," said Lynn Rosentrater, a climate-change officer with the World Wildlife Fund in Norway. "It's going to happen, so we need to plan for it."

The once-deadly route has been re-christened "Panama Canal North" by shippers eager to shave nearly 5,000 miles off the trip from Europe to Asia. Already, a parade of strange ships and faces is streaming through the passage. Canadian transit officials who monitor the route dub the newcomers "UFOs," for "unaccustomed floating objects."

These have included, in the last few years, a Russian tug that dragged a five-story floating dry dock through the passage, adventurers skimming through in sleek sailboats, and a boatload of Chinese sailors that arrived unannounced in the Arctic village of Tuktoyaktuk, disembarked to take photographs, and left abruptly when a local Mountie arrived.

Last summer, the Canadian navy sent warships north of the Arctic Circle for the first time since the end of the Cold War. And U.S. naval officers are circulating a report called "Naval Operations in an Ice-Free Arctic" that discusses, among other things, the need for a new class of ice-strengthened warship to patrol newly opening Arctic waters.

With each summer warmer than the last, and with species such as dragonflies and moose showing up for the first time, many here are bracing for a stranger, warmer world. Unlikely as it seems in a town where residents still skin and dry seals in their front yards, some of those taking a long-range view hail this remote outpost as the next Singapore.

"If it's handled correctly, you sit on an international strait, take a proactive stand and profit nicely," said Rob Huebert, the associate director of the Center for Military and Strategic Studies at the University of Calgary.

The passage wasn't traversed until 1906, when legendary polar explorer Roald Amundsen completed the trip in three years. The feat was not accomplished again until Canadian Mountie Henry Larsen took a schooner with a hull made of 2-foot-thick Douglas fir through the passage and then back again in the 1940s.

That was before the ice started its retreat.

The Canadian Ice Service reports that Arctic ice has disappeared at a rate of about 3 percent each decade since the 1970s. It is getting thinner as well.