How warming affects Arctic sea ice, polar bears

The polar bear, majestic, hungry, and at risk of disappearing is dependent on sea ice melting on our warming planet.

The polar bear is a unique creature in the harsh, unforgiving Arctic where frigid temperatures are not only a way of living but a necessity. But where it lives, where it hunts, where it eats — it’s disappearing underfoot in the crucial summertime.

“They have just always been a revered species by people, going back hundreds and hundreds of years,” said longtime government polar bear researcher Steve Amstrup, now chief scientist for Polar Bear International. “There’s just something special about polar bears.”

Scientists and advocates point to polar bears, marked as “threatened” on the endangered species list, as the white-hot warning signal for the rest of the planet — “the canary in the cryosphere.” As world leaders meet in Glasgow, Scotland, to try to ramp up efforts to curb climate change, the specter of polar bears looms over them.

Inger Andersen, the head of the United Nations Environment Program, was previously the International Union for the Conservation of Nature. This organization monitors and classes species in trouble. She asks: “Do we really want to be the generation that saw the end of the ability of something as majestic as the polar bear to survive?”

The state of sea-ice

This July 2012 photo provided by Polar Bears International shows polar bears near Svalbard, Norway. In the summertime, polar bears go out on the ice to hunt and eat, feasting and putting on weight to sustain them through the winter.
Polar Bears International’s July 2012 photo shows polar bears close to Svalbard in Norway. Polar bears spend the summer on the ice hunting and eating, and then gain weight to sustain them throughout the winter.

Arctic sea ice — frozen ocean water — shrinks during the summer as it gets warmer, then forms again in the long winter. Global warming will affect how much it shrinks, scientists claim. Because the ice is thinner in the first year, the sea ice shrinks more in summer.

Julienne Stroeve is a University of Manitoba researcher. She believes that summers without sea-ice are inevitable. Her opinion is shared by many other experts.

Waleed Abdalati, a former chief scientist at NASA, is now a leading University of Colorado environmental researcher.

“That’s something human civilization has never known,” Abdalati said. “That’s like taking a sledgehammer to the climate system and doing something huge about it.”

This 2020 photo provided by Polar Bears International shows polar bears in Churchill, Manitoba, Canada during migration.
Polar Bears International provided this 2020 photo of polar bears in Churchill Manitoba, Canada, during migration.

The warming already in the oceans and in the air is committed — like a freight train in motion. The Earth will soon see a summer without more than 1,000,000 square kilometers of sea-ice scattered in tiny pieces across the Arctic.

The big question is when the Arctic will “look like a blue ocean,” said Mark Serreze, director of the National Snow and Ice Data Center.

Experts say it could be as soon as the 2030s. Most likely, in the 2040s.

The Arctic has been warming twice the rate of the rest of the globe. John Walsh, University of Alaska at Fairbanks scientist, stated that the Arctic has warmed up three times faster than the rest of Earth in some seasons.

That’s because of something called “Arctic amplification.” Essentially, white ice in the Arctic reflects heat. Scientists say that when it melts, the darker sea absorbs more heat which warms the oceans faster.

Polar bear connection

This June 2018 photo provided by Polar Bears International shows polar bear standing on sea ice north of Svalbard, Norway.
Polar Bears International provided this June 2018 photo of a polar bear standing on the sea ice north Svalbard (Norway).

There are 19 different subpopulations within the Arctic of polar bears. Each one is different. Some are in serious trouble, especially those at the southernmost, while others are stable. Their survival is heavily dependent on sea ice.

“As you go to the Arctic and see what’s happening with your own eyes … it’s depressing,” said University of Washington marine biologist Kristin Laidre, who has studied polar bears in Baffin Bay.

Shrinking sea ice literally means shrinking the polar bears.

Polar bears are known to go out on the ice in summer to hunt and eat. They also gain weight to support them through winter. They prefer areas that are more than half covered with ice because it’s the most productive hunting and feeding grounds, Amstrup said. They can move more freely and eat more if there is more ice.

The bears enjoyed a buffet on the ice of seals and whales 30-40 years ago.

In the 1980s, “the males were huge, females were reproducing regularly and cubs were surviving well,” Amstrup said. “The population looked good.”

With ice loss, the bears haven’t been doing as well, Amstrup said. One sign: A higher percentage of cubs die before their first birthdays.

Polar bears are land mammals who have adapted to the sea. The animals they eat — seals and walruses mostly — are aquatic.

Bears do best when they are able to hunt in shallow water, which is usually close to land.

“When sea ice is present over those near-shore waters, polar bears can make hay,” Amstrup said.

In recent years, however, the sea ice has been retreating offshore in most summers. That has forced the bears to drift on the ice into deep waters — sometimes nearly a mile deep — that are devoid of their prey, Amstrup said.

The striking contrast between Alaska’s Beaufort Sea polar bears and the Chukchi Sea polar bears can be seen off Alaska.

Go 30 to 40 miles offshore from Prudhoe Bay in the Beaufort Sea “and you’re in very unproductive waters,” Amstrup said.

Further south in the Chukchi, it’s shallower, which allows bottom-feeding walruses to thrive. He said that this provides food for polar bears.

“The bears in the Chukchi seem to be faring pretty well because of that additional productivity,” Amstrup said. But the bears of the Beaufort “give us a real good early warning of where this is all coming to.”

The future

This July 2012 photo provided by Polar Bears International shows polar bears in near Svalbard, Norway.
Polar Bears International, July 2012 photo showing polar bears in Norway’s near Svalbard.

The scientists who observe the polar bears and monitor sea ice know that much of the warming is already in motion, even as world leaders meet in Scotland.

There’s a chance, if negotiators succeed and everything turns out just right, that the world will once again see an Arctic with significant sea ice in the summer late this century and in the 22nd century, experts said. But until then “that door has been closed,” said Twila Moon, a National Snow and Ice Data Center scientist.

So, too, is the hope melting.

“It’s near impossible for us to see a place where we don’t reach an essentially sea ice-free Arctic, even if we’re able to do the work to create much, much lower emissions” of heat-trapping gases, Moon said. “Sea ice is one of those things that we’ll see reach some pretty devastating lows along that path. And we can already see those influences for polar bears.”

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