Set aside for a moment those iconic images of a skinny polar bear drifting on a splinter of sea ice, hungry and forlorn.

That’s an anachronism, an incomplete image of what’s going terribly wrong at the top of the world.

Picture instead a cream-colored bear loping on land, across tundra, and along the pebbled shores. She’s irritable, putting wildlife scientists – also in this scene, playing cameo roles – in serious danger.

The shaggy predator is ravenous, as the ice platform, from which her pie-plate sized paws have long seized seals for dinner, is getting rarer year by year. Today, the bear fed on eggs raided from ground-nesting birds.

Polar bear raids on bird colonies a ‘new normal’

Today, polar bears are raiding bird colonies around the Arctic. That used to be rare.

Benoît Sittler, a French geographer who has studied eastern Greenland for three decades, says Arctic ecosystems, stressed already by higher temperatures, and diminished, low-quality snow falls, could be in the midst of cascading ecological destruction.

Sittler first flew to Traill Island, above the Arctic Circle in eastern Greenland, in 1988 to study the quadrennial boom and bust population-cycle of the hamster-size collared lemming. He had no idea that within two decades his study subject would have nearly disappeared from his research site, and that he would go on to chronicle an ecosystem’s death spiral.

A research scientist at the University of Freiburg, Sittler says government funding agencies rarely back long-term wildlife observations like his. He’s been creative about funding his annual Arctic expeditions, supporting them mostly with contributions from Polar philatelists, stamp collectors who prize correspondence posted from the northern- and southern-most parts of the planet. Each year, Sittler mails from the Greenland mainland scores of envelopes, each inked with an expedition logo and signed by the scientist and that season’s crew of four or five volunteers. Sittler’s project earns about $20,000 annually from the collectors.

In 2003, I hitched a ride to Traill Island in a Twin Otter, a rugged plane revered by adventurers traveling to the most inaccessible destinations near the north and south poles. It vibrated violently as it touched down on a patch of tundra that Sittler had cleared of brush and had marked with flags. He smiled warmly from under a bulky wool cap.

We unloaded boxes of food into the camp kitchen, a former trapper’s cabin the size of a suburban tool shed.

With that year’s team of grizzled researchers, I slogged along Traill Islands’ barren shores and picked through the boulder-strewn interior.

One night we ate dried potatoes mixed into reconstituted broth. A crew member had picked sour sorrel leaves and simmered them with powdered milk. Every day we searched for lemmings and the rodents’ predators: Arctic foxes, ermines, and snowy owls.

At that time, two decades into his study, Sittler had documented three lemmings spikes – in 1990, 1994 and 1998 – when the population grew by a factor of about 200. He had confirmed findings from elsewhere that predator numbers peak the following year, foretelling a lemming collapse. A lemming explosion anticipated the summer before hadn’t materialized. He’d written by email that the island could be thick with the fist-size rodent. But I didn’t see a single specimen of the animal, and Sittler wouldn’t spot any that year.

Fewer lemmings, more polar bear sightings

A small number of lemmings still live on Traill Island, but the population booms that Sittler recorded in the 1990s appear to have ended. He believes that altered snow conditions favor the Arctic rodents less.

“Lemmings like light powder snow,” he said in a recent phone call. During the summer, they burrow into the soil. In winter, they live above ground, tunnel networks they excavate in the snow. But the snow in recent winters has been heavy and wet. During cold snaps it has frozen hard. Lemmings can’t penetrate that.

While the number of lemmings and of the carnivores that eat them have dwindled, sightings of polar bears on Traill Island have gone way up. In his initial 13 years, Sittler says he found bear tracks once, and several times spotted bears on sea ice. During those years, he saw a polar bear on land only once. “We dreamed of seeing bears,” he said.

Then, around 2004, the bear invasion began, and bears became regular guests at his camp. They showed up on the coast and stayed. In the years since, they’ve arrived ever earlier and have remained longer. And they’ve lumbered more than a mile inland.

Emergency supplies, pepper spray

“Problem bears” hang around his campsite and break into cabins he’s stocked with emergency supplies. Sittler has long carried a 30-06 rifle, flare guns, and pepper spray, as do most visitors to such areas. Now, he also protects his tents with two concentric security rings: an electric fence and, farther out, a mine field equipped with explosive charges designed to scare intruders and alert his crew.

With such precautions, Sittler and his team have remained safe. But not so Traill Island’s Arctic terns. Every year, Arctic terns take the longest migration of any animal on Earth, a 40,000-mile round-trip flight from Greenland to Antarctica and back. Lately, the bears have been stealing eggs from the birds’ pebble and stick nests. The colonies of terns have now stopped breeding on gravel bars near Sittler’s camps. He doesn’t know if the adults have found safer quarters elsewhere.

So much change over so little time

Polar bears, displaced by shrinking sea ice, increasingly have had to become land predators, disrupting wildlife all over the Arctic.

Two Canadian biologists have reported more frequent polar bears sightings near thick-billed murres nesting on cliffs in northern Hudson Bay. In 2011, bears there raided a colony of 20,000 breeding murre pairs causing “mass panic.” The bears killed between 200 and 500 adults and destroyed 30 percent of that season’s eggs.

And then, in March 2015, Dutch ornithologist Jouke Prop and several other European scientists, including Sittler, published a paper describing polar bear raids on colonies of common eiders, glaucous gulls, and barnacle geese on Spitsbergen Island, in the Svalbard archipelago far north of Norway’s mainland.

According to Prop, who has studied those birds since 1977, bears had rarely been seen near his colonies until about 2000. Since then, the number of “bear days” has grown exponentially.

Between 2004 and 2012, bears destroyed 91 percent of the barnacle geese eggs laid there. In a recent phone call, Prop said that the geese can’t stop the invaders and don’t try. A bear “walks from one nest to another taking one egg after another: one minute per egg.”

Between 2009 and 2014, bears in the same region also killed 93 percent of glaucous gull chicks, which generally hatch shortly before bears arrive. Common eiders fared poorly too.

Sittler and Prop each say that they’ve been astounded by the transformation they’ve documented at their study sites. “I could never have imagined that such changes could happen in so little time,” said Sittler.

Neither expresses much optimism about the future, though both plan to keep observing what happens.

Lately, anticipating the springtime bears, Sittler has added a new item to his luggage: extra panes of glass. “Every summer they break a window” in his cabin, he says. “We’re prepared to get it mended.”

Feature photo (top of posting) courtesy of Norwegian adventure sailor Andreas Heide (www.barba.no) while pargliding above Svalbard in 2015.