On a Saturday morning in late November in Kotzebue, Alaska, a village 33 miles north of the Arctic Circle, two Inupiat men nursed cups of coffee at the Bayside Inn. They stared out a window at Kotzebue Sound, an arm of the Chukchi Sea at the southern edge of the Arctic Ocean. Outside it was 35 degrees and raining. "Too warm," said one of the men.

His companion let a long silence pass. Then he nodded. "Too much rain," he said.  Indeed.

In Kotzebue, November temperatures normally hover in the single digits. But these aren't normal times. This is the time of "the changes" — a term used by Caleb Pungowiyi, former president of the Inuit Circumpolar Council and one of Kotzebue's most respected elders, when talking about the effects of climate change in the Alaskan Arctic.

"Some events like this happen occasionally," Pungowiyi told me as we sat looking out at the rain. "But for something to happen that's this warm, in November, for a number of days — these kinds of temperatures are not normal. We should be down in the teens and minus temperatures this time of year."

A few days of rainy weather isn't climate, but it is a powerful data point. You get enough warm, rainy days like this, and pretty soon they add up. This is how climate change happens in the far north: one warm rainy day at a time.

The thawing of the far north is one of the signal ecological events of our time. Global temperatures rose an average of 1.18 degrees Fahrenheit from 1905 to 2005, but that increase wasn't evenly distributed.

The Arctic took the brunt of it, warming nearly twice as fast as the rest of the planet. Since 1980, winter sea ice in the Arctic has lost almost half its thickness.

In Kotzebue, the mean winter temperature has climbed more than 6 degrees in the past 50 years. Permafrost is thawing in patches all over the Arctic.

"What we're doing with climate change," says Brendan Kelly, a former University of Alaska biologist who is now deputy director of the National Science Foundation's Arctic Sciences Division, "is carrying out a long-term scientific experiment at continental scale."

Resilience of Arctic Food Web Being Tested

To get a sense of how that experiment is unfolding, it's helpful to take a look at one of the most fundamental acts of life: eating, the passage of energy from one living organism to another. Predators and prey form a food chain — plant to insect to rodent to carnivore to apex predator. Those chains interlock to form webs.

"To protect Nature," the conservation biologist Stuart Pimm wrote in his seminal book Food Webs, "we must have some understanding of her complexities, for which the food web is the basic description."

"Basic" is an apt word. Many Arctic organisms are extremophiles — specialists adapted to thrive at temperatures so low they would kill most other species. It's a club with few members. Species diversity is low, so Arctic food webs are simple. And in the age of climate change, simple is not a good thing to be.

"The more complicated and interconnected the food web, the less damage you can expect if one or two species are lost," explains Deborah Bronk, a biological oceanographer and specialist in nutrient cycling at the Virginia Institute of Marine Science at the College of William & Mary. "In these very simple food chains, if you lose one species you can really mess up the whole thing."

Complexity yields resilience. Without resilience, there's risk of a crash. Scientists who study trophic cascades, in which the loss of a single species sets off a reaction throughout the food web, report that this sort of crash generally happens in low-diversity ecosystems, where one or a few species exert great influence.

That describes the Arctic marine and coastal food web.

During the past few years a number of disturbing reports from the Arctic have appeared in scientific journals. Increasingly, acidic seawater may be affecting the ability of crustaceans to form their shells. Warmer-water fish are invading waters traditionally inhabited by cold-water fish. More seal pupping dens are collapsing because of earlier springs and diminished snow cover. Starving polar bears have been seen scavenging berries, grass, moss, and goose eggs.

As ice disappears, walrus colonies are increasingly hauling out on land, where polar bears — also on land because of the lack of ice — have been observed attacking them.

Humans, a big part of the Arctic food web, are experiencing impacts as well. Their hunting seasons are changing, their travel routes becoming more dangerous and unpredictable. The resilience of the Arctic food web is now being tested. To paraphrase Brendan Kelly: In an ecosystem perfectly adapted to sea ice, snowfall, and permafrost, what happens when those elements begin to disappear?

Kotzebue seemed like a good place to find out. Its 3,200 residents — almost three-quarters of them Inupiat — aren't mere observers. As Caleb Pungowiyi told me, people in Kotzebue are acutely aware that ice and snow are to the Arctic what soil and rain are to the temperate latitudes.

"We depend on ice freezing up in the fall and the snow accumulating on top of it in fall and early winter" for everything to work, he said. "But now we're seeing a lot less of both."

What's Changing? Chemistry of the Sea Itself