Step over the imaginary dotted line

What makes the allure of an imaginary dotted line so irresistible? I had flown through forest-fire smoke in a tiny prop plane, been jostled along a gravel road on a bus, and battled hordes of relentless mosquitoes - just to step across the Arctic Circle.

My husband and I were on a 12-hour expedition that departed from Fairbanks, 160 miles south of the circle. Aside from bragging rights and mosquito bites, what did we get out of the trip? Spectacular scenery, a chance to explore the fabled Alaskan tundra, and an up-close look at the controversial Trans-Alaska Pipeline System as it snakes across the wilderness.

Our nine companions hailed from as near as Anchorage and as far away as Italy and Japan.

Not being a fan of group tours, I'd resisted joining this jaunt. But after phoning a company that recently started renting cars outfitted for the gravel-covered Dalton Highway (the only way to get to the circle besides flying), I relented. Their comments were a bit daunting: "We give you two spare tires, but after that it's your responsibility," and "A chip in the windshield will cost you $40, but to replace the whole thing is about $400."

True, they throw in a CB radio, but the anticipated fun of uttering phrases like, "Ten-four, good buddy, this is my third flat tire," just didn't compensate.

The flight up revealed mountains of pine forests, giving way to vast rolling hills of emerald tundra marked with kettle lakes These are formed when the tundra is damaged, causing the permafrost to melt. We could have been flying over the putting greens and water hazards of a gigantic golf course.

Our guide, Tom, described the delicate relationship between tundra and permafrost, soil that has remained continuously frozen for at least two years.

"The sphagnum moss of the tundra is five to 10 inches thick and acts as insulation for the permafrost," he explained. "Just driving a truck across it can disrupt it enough to create lakes along the wheel tracks." Damage to the tundra sets off a chain reaction of permafrost melt, lake formation, tree growth - and eventually a different landscape emerges.

"We just crossed the Arctic Circle!" the pilot interrupted. His instrument panel and read 66 degrees 32 minutes on the global positioning system.

Dave brought the plane in for a landing 23 miles north of the circle, on a remote airstrip originally built to receive pipeline construction supplies.

The sign on a tiny locked hut proclaimed it as Prospect Creek International Airport, a remnant of the days when this was allegedly one of the busiest airports in the United States. Now Prospect Creek serves pumping station No. 5 on Mile 275 of the pipeline, which stretches from Prudhoe Bay in the north down to the port of Valdez in the south.

While we waited in the summery Arctic chill for our bus to arrive, Tom told us that the airstrip was built from packed gravel over Styrofoam blocks, which act as insulation to keep the permafrost from melting and turning the landing field into a swamp. The Dalton Highway was built much the same way when construction started back in 1968.

Before long, the bus rolled up and let off its passengers, who would return on the planes we'd come in. Tom took his place behind the wheel of the 25-passenger coach, assuring us that buses and trucks rarely get flats, because of their larger, tougher tires. "But if you're in a van, it's typical to get a flat at least once in each direction," he added.

As he launched into a wide-ranging monologue on everything from pipeline construction to natural history to gossip about the characters who ply the Dalton, I realized another good reason not to drive by ourselves. His stories made the long, bumpy ride come alive, whether he was unreeling facts (caribou will eat 223 types of tundra plants; a million barrels of oil a day are currently moving through the 801.2 miles of pipeline at 5.4 miles per hour), or spouting local lore.

An hour into the drive, we had our "on-the-ground" encounter with the Arctic Circle, which was marked by a turnout on the road, a large placard, and an outhouse.

As we trooped over to the actual circle, Tom unfurled a red carpet, bisected by a yellow, dotted line. He carefully explained the proper technique for crossing over: right foot first, right hand extended to shake the hand of the person welcoming you to the other side, smile for the camera.

One by one, we crossed the imaginary line as expedition members snapped photos and passed cameras back and forth. It was silly but fun - except that we found ourselves batting at the pesky mosquitoes that also seemed eager to welcome us.

With the Arctic behind us, it was time to settle in for an Alaskan road trip. I took a turn riding shotgun next to Tom, and learned more about the Dalton Highway. Originally a private pipeline company road, it opened to the public in 1996 when it and responsibility for its maintenance were turned over to the state.

In the heyday of pipeline construction, 400 to 500 trucks barreled along the Dalton every day. There are still plenty of them. At a speed of 50 miles per hour, they kick up a lot of gravel - our bus sported a windshield chip that was blossoming into a foot-long crack. There is a master plan to have the entire Dalton Highway paved by 2010, but it's slow going because asphalt is tricky to lay without damaging the permafrost.

Our next stop was for a close-up look at the pipeline. We pulled off and trooped over to the zigzagging monster. To protect the permafrost and allow for animal migration, it is suspended for much of its journey, held aloft by 78,000 vertical supports that wick heat out of the ground and dissipate it through aluminum radiators filled with ammonia gas.

The pipeline rests on Teflon-covered slides, so it can expand (up to 100 yards in the summer) or survive an earthquake.

This stop was also a chance to tread gently on the tundra, which felt like walking on a huge, springy mattress. Tom dug out an eight-inch plug of turf and let us have a quick look at the dark permafrost earth underneath. Even in that small amount of time, we could see water starting to form as the permafrost met the air. Tom replaced the insulating tundra and we gingerly moved on.

After bumping along for another couple of hours, we reached our dinner spot beside the Yukon River. While we ate, we also provided dinner for hordes of mosquitoes. I held my sandwich and paced back and forth, because movement kept them from landing. Even when we took refuge inside the bus, swarms of bloodsuckers swept in with us.

This provided an opportunity for international teamwork as we used napkins to crush as many of the critters as possible.

"What is mosquito in Italian?" I asked the couple behind me.

"Zanzara," the man replied.

"In French, it is moustique; I am originally from France," his wife piped up.

"Kaa," the Japanese diplomat weighed in.

There's nothing like bonding over a common enemy. I contemplated how shipping a few billion of these mosquitoes to the Middle East might help the peace process.

Once the mosquito situation was under control, we headed across the Yukon River, fifth largest in the world by volume. This point is the river's only bridge crossing in the US, about a half-mile in width. At some spots, the Yukon spreads out to run 20 miles wide. Since this is also where the pipeline crosses the river, there is a gate in the water that can be closed in the event of an oil spill.

Finally, we were on the home stretch. The stunted, scraggly Taiga forests that battle for a foothold in the permafrost started to give way to more normal-looking spruces. We began to see signs of homesteads and remnants of gold mines.

As we neared civilization, we bade farewell to the Dalton and eased onto the Elliot Highway. We pulled in to Fairbanks around 12:30 a.m., not long after sunset. My head was buzzing with all the facts and sights of a trip that turned out to be far richer than the mere novelty of crossing a dotted line.

The final event of the night was the awarding of Arctic Circle crossing certificates. They were adorned with various flora and fauna, the pipeline, and the Alaska state flag.

Just one thing was missing. "What about the mosquitoes?" I wondered as I neatly fanned a few aside with my new certificate.