PITSBERGEN, Norway -- The polar bear is 3 years old and hungry. "Ursus maritimus" has spent two years with his mother, and now on his own, he prowls the shoreline of an Arctic island, his fur the yellow-white of summer. He is vulnerable to the appetites of older and larger bears; this first year on his own may be the most treacherous in his life.

We watch from our ship's deck as he strides, his huge front paws landing surely on shoreline scree. He's not 100 yards off the bow of the National Geographic Endeavour, where our cameras are clicking so furiously it sounds like cicadas on a summer's night.

It is a summer's night, but at 79 degrees North latitude, the season is rendered in pewter, silver, gray and white, edged with shocking turquoise from light bouncing among compressed ice crystals in glaciers and floating bergs.

As our ship pushes through pack ice into a white wilderness, we enter a land where glaciers have retreated but never disappeared. We are looking at the planet as it was 10,000 years ago, gouged and worn by the great moving rivers of ice. We'll spend a week exploring the High Arctic around the archipelago of Svalbard, where Spitsbergen is located, then sail for another week through the spectacular Norwegian fjords that were carved, polished and abandoned by that same ice.

In a warming world, it's a vital time to see and tell about this ecosystem of ice, to watch it shape the rock, push the moraine, shed its meltwater in ever increasing gushers. Our own trip was planned two years in advance as reports of climate change grew more dire. Once here, we find glaciers melting faster than the snowfall can feed them, due to temperatures that have been rising since the 1970s. Last summer, in 2007, there was hardly any sea ice at all, say our naturalists; by this early summer of 2008, ice has returned.

Polar bears are still healthy here, but the fjord that leads to Spitsbergen's largest town has not frozen in three years and there is worry about the future. Polar bears are now a threatened species in the Canadian Arctic because of global warming. Summer ice has been so reduced that bears cannot hunt seals successfully or swim the great distances between ice shelves.

The islands of Svalbard are half way between Norway and the North Pole. About 2,000 people live here in small settlements, as do many of the 2,000 or 3,000 polar bears that surround the Barents Sea.

Bundled, coddled and indulgently provisioned, we are the merest shades of hardier sorts who preceded us: Vikings in the 12th century, the Dutch in 1596, and legendary polar explorers Nansen and Amundsen. Hunters and trappers of whales, seals, bears, foxes and walrus have left their bloody marks over centuries; coal miners battle the elements still into the black tunnels under Spitsbergen.

John Longyear, an American, opened a coal mine on Spitsbergen in 1906, and the ragged little town of Longyearbyen is named for him. (The town's 21st century attraction, aside from scientists studying climate change at the northernmost university, is the global seed vault that safeguards the world's agricultural diversity in a frigid mountainside.)

Miners and glaciologists alike carry firearms here, not against man, but because polar bears can pose danger -- males may reach 1,500 pounds and rear up to 10 feet. The local shops, which we visit after lunch at the Radisson's Polar Hotel, reassuringly prohibit firearms. Our ship, anchored in the fjord, is reached by inflatable rafts called Zodiacs.

On this Lindblad Expedition aboard the National Geographic ship, we number 106 passengers, 70 crew, a dozen naturalists and two magazine photographers. Jim Richardson from National Geographic and Richard Maack, former photo editor of Arizona Highways, teach and critique as we go along, and an impassioned band of wanna-be camera geeks quickly materializes.

After our first on-shore bear, adrenaline spikes again with a midnight sighting. Sleep is interrupted with "Polar bear off port bow." Silent, sleepy and thrilled, we scramble to deck and watch in awe. Then, after breakfast, another bear draws us back outside.

Throughout the shifting pack ice, the bears move unhurriedly, pausing to lie down, yawn, test the air for smells of seal. Exquisitely adapted to this environment, they can run for a short distance but overheat easily; no wonder that they prefer sedentary hunting at seal holes in ice. They can sniff out a seal several miles away and know from bubbles that appear in breathing holes when dinner is soon to appear. Insulated against icy water with layers of fat and hair that is hollow, ice bears are able to swim for hours at a time. They are followed by ivory gulls and gray-on-white glaucous gulls, hangers-on hoping for scraps.

Our midnight bear saunters to an already devoured seal's remains and nibbles on bloody tidbits. The late morning bear slips into the sea and swims away.

We sail on to Cape Fanshaw on Spitsbergen's northeastern shore, lingering to watch nesting seabirds. Thousands of black and white Brunnich's guillemots crowd the narrow cliff ledges. Diving for small fish, they literally fly underwater. Less than graceful on the water's surface, they need a running start to lift off. Chunky little birds, the guillemots lay pointed or conical eggs that roll in circles rather than off the ledges.

Fanshaw's cliffs plunge directly into the sea, where bird guano fertilizes the waters below. Diver David Cothran shoots video footage of the gloriously rich gardens of anemones and sea stars fertilized from above and wows us at one of our cocktail hour recountings of daily adventures.

Later, we sail in a hush along the edge of the Austfonna ice cap, the third largest in the world. Meltwater gushes from its blue-tinted arteries, and thick fog slips over the cap, moving silkily in the still light night.

Norway-born Carl Erik Kilander, armed with a rifle, guides a hike on the island Nordaustlandet. Permafrost a few feet below the surface allows the tundra to retain enough water for grasses and flowering plants to grow, flower and set seed in the brief summer. And here we find reindeer and arctic foxes, and listen to rather sweet, high sounds snow buntings, the only song birds of the High Arctic.

From a distance, Nordaustlandet appears bleak and rusty brown, with swaths of snow clinging to hillsides and icy rivers streaming to the sea. Once ashore, we find the rusts are really the pink, yellow and red flowers of saxifrages, chickweeds, willows and moss campions. In this arid, wind-swept landscape, the plants grow in pincushion-like clumps, barely three or four inches tall, and are pollinated by flies, mosquitoes or midges. Some insects nestle in the center of the Svalbard poppies, soaking up the warmth from petals reflecting sunlight.

The tundra is rich with grasses in midsummer, and reindeer are feasting nonstop, fattening themselves for winter. Smaller than any other reindeer, their gray fur is thicker as well in order to survive this far north. They have shed long strings of it on the flowers. As glaciers retreat, mosses and small plants take root, eventually followed by wild geese, ptarmigans and reindeer.

Here and there sit silvered wooden boats and shacks of hunters, abandoned and collapsing. In the shadow of one hut, two herds of male walrus have hauled up to molt. From a distance, they resemble brown suede beanbags; closer up, they are enormous animals of impossible design. How can they function with such handicaps as two-foot canine teeth and only flippers to wrestle a ton of fat and muscle onto shore? Hunted to near extinction, Atlantic walrus are gradually recovering around Svalbard. Our naturalists keep us a good distance away and speak in whispers.

Halfway between Svalbard and Norway is Bear Island, the largest seabird rookery in the North Atlantic. Gulls and murres, auklets, kittiwakes, fulmars and skuas swirl is every direction, never once colliding in this snow globe come to life.

Even as we cross the Barents Sea, there are surprises: Sperm whales. These largest of the toothed whales blow at 45 degrees to the left, and we are lucky to spot a pair that stays up to breath deeply several times before diving to feed. After each dive they plunge 5,000 feet to hunt squid and skates; we wait 30 minutes to see them again.

Finally we reach the shores of Norway, where we disembark at Tromso. This is where Roald Amundsen -- who used dogs to outrace Scott to the South Pole -- recruited men for his expeditions to both poles. This also is home to the Sami, the indigenous people who are traditionally reindeer herders. To get our land-legs back, we tour a Sami museum and the Cathedral of the Arctic, designed to resemble a Sami tent. The northernmost botanic garden in the world is also in Tromso, and even on a gray afternoon, the four acres are ablaze with poppies, the flowers of succulents, rhododendrons, lilies and iris.

Though it's the ice and bears we've really come to see, the second half of the journey proves conventionally beautiful. We kayak in fjords, hike in boreal forests of beech and wildflowers, climb to the Briksdalbreen glacier's narrow blue tongue where the wind blows fierce and cold and waterfalls are wild with froth and mist.

We toast Stetinden, Norway's national mountain soaring nearly 4,000 feet into anvil-topped splendor; we stop in A, a cod-fishing village pronounced awe, where salted cod, stock fish and cod liver oil are produced. We find a trio of helmeted Vikings who offer us grog as we take our last Zodiac ride.

In the age of Viking expansion, the world was warming and pack ice melting. Perhaps we have set into motion another type of Viking era. But to see the glories of this white world, its best to get here soon.

VISITING THE ARCTIC

More tourists are visiting the Arctic than ever before as climate change brings threats to the region into the news.

Lindblad Expeditions, which has been in the travel business since the 1950s, teamed with National Geographic in 2004 to offer special trips with National Geographic experts and photographers. Our Arctic trip, called "Beyond the North Cape: Norway's Fjords and Arctic Svalbard," was a 16-day journey. We paid $20,000 for two, including a fuel surcharge of $130 each.

In 2009, the Endeavour will be transferred to the Galapagos and a new ship, the Explorer, will be used for two Arctic voyages, in June and again in August. The prices begin at $9,680 per person.

Included are all meals, kayaking, Zodiac rides, the guided hikes and wildlife viewing, use of the library and gym, and a high-def video as a take-home record of the trip. Cocktails and wine at dinner are extra, as are laundry and tips for the staff (recommended to be a minimum of $12 a day).

The Norwegian cities of Oslo and Bergen, where our trip began and ended, are expensive, and a simple evening meal in Oslo -- one pizza, one salad and one bottle of wine -- cost $144. We quickly learned to buy sandwiches in the delis and to pack lunches (bread and cheese from hotel breakfast buffets) when heading out to see the sights. In Bergen, we booked a budget Thon hotel that was within walking distance of the main waterfront shops and restaurants.

Lindblad offers several other Arctic cruises that explore Greenland, Baffin Island and the Canadian High Arctic. Details: 800-EXPEDITION, www.expeditions.com.

Here is a sampling of companies that offer cruises to Spitsbergen and the Arctic:

• Quark Expeditions has a dozen Arctic voyages that includes not only Spitsbergen, but the North Pole, and various routes taken by Arctic explorers when searching for the Northwest passage. Helicopter rides are included on some trips. Prices range from $3,390 per person to $33,390. 800-356-5699, www.quarkexpeditions.com.

• Spitsbergen Travel, located in Longyearbyen on the island of Spitsbergen, offers everything from dog sled trips to winter snowmobiling. www.spitsbergentravel.no/eng.

• World Expeditions has six trips around Spitsbergen, varying in length from eight to 20 days. The longest cruise includes Greenland and Iceland as well as Spitsbergen. A twin cabin begins at $8,182 for two. 800-567-2216, www.lonelyplanet.worldexpeditions.net.

• Nordic Travel is Russia-based, with trips sailing roundtrip from Moscow. The itinerary aboard the icebreaker Yamal includes the North Pole and helicopter rides. The rate for 2009 begins at $21,700 per person. Other itineraries go to Spitsbergen and Franz Josef Land. www.nordictravel.ru.

• Exodus, an English company, has Spitsbergen trips aboard two different ships. Eleven day trips begin at $5,910 per person. 800-843-4272, www.exodus.co.uk.

• Hurtigruten offers a five-day, nine-day or 16-day cruise around Spitsbergen. Rates begin at $2,800 per person. 800-334-6544, www.cruisenorway.com.