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https://apple.news/AId0AtkldRPyK2amerbuFHA [how can a bear survive if it must swim 109 miles for food to eat?]
The Arctic could become ‘ice-free’ within a decade, sooner than projected, study says
by Doyle Rice for USA TODAY, published March 5, 2024
The Arctic could be “ice-free” in the summertime as soon as the next few years, scientists said in a study Tuesday. That’s the earliest date any study has suggested an ice-free Arctic could occur – as many as 10 years earlier than previous projections.
The ice in question is seasonal sea ice, which freezes each winter but melts in the summer. The amount of summertime sea ice has been in decline for years because of human-caused global warming.
What scientists refer to as the first “ice-free” Arctic summer year will occur when the Arctic has less than 386,000 square miles of sea ice.
“Ice-free conditions could occur as early as the 2020s and 2030s,” study lead author Alexandra Jahn, of the University of Colorado, told USA TODAY. Jahn said greenhouse gas emissions are the main contributors to sea-ice loss.
Specifically, the study projects that the Arctic Ocean could become ice-free for the first time on a late August or early September day in the 2020s to the 2030s under all future emissions scenarios.
What is sea ice? Why is it important?
Sea ice is frozen ocean water that melts each summer, then refreezes each winter. Sea ice in the Arctic has been declining for years, particularly during September, when it typically reaches its lowest coverage of the year.
Earlier research projected it would be virtually ice-free by late in the century if higher greenhouse gas emissions continued unabated.
Sea ice affects Arctic communities and wildlife such as polar bears and walruses, and it helps regulate the planet’s temperature by influencing the circulation of the atmosphere and ocean.
What does this mean for the the Arctic’s animals and people?
“A decreasing sea ice cover threatens the survival of ice-adapted species like polar bears, who depend on sea ice to hunt,” Jahn told USA TODAY. “So the longer ice-free conditions last, the more the survival of polar bears is threatened.
https://cm.usatoday.com/article-body/inline-desktop_120123_DecBAU
“For people living in the Arctic, the decline of Arctic sea ice affects how long they can travel over the frozen Arctic Ocean − as well as affecting coastal erosion, which can threaten seaside villages as larger open water areas lead to increases in wave heights.”
How else does sea ice affect us?
What happens in the Arctic doesn’t stay in the Arctic, scientists have said. Indeed, Jahn said, “other studies have shown that the loss of summer sea ice in the Arctic has the potential to affect weather in the U.S. as well as increase wildfire risks in the western U.S.”
An ice-free Arctic Ocean in the summer also would make the Arctic much more accessible for shipping, mining and tourism, she said.
What do others say about the study?
Walt Meier, a senior research scientist at the National Snow and Ice Data Center, who was not involved in the new study, told USA TODAY that the study’s methodology was sound. But, he said, “there are still uncertainties in the models and potential bias in how they predict future sea ice conditions. So any kind of projection is going to have pretty high uncertainty, particularly in predicting a specific year of ice-free conditions.”
In addition, he said, although an ice-free Arctic is possible this decade, it is “not likely.”
“The mid- to late 2030s is more plausible, at least as far as having one year reach an ice-free state,” Meier said.
What is the timetable for the sea ice loss?
If the world continues on its current emissions path, the Arctic might become ice-free only during late summer and early fall from August to October, the study said. But under the highest emissions scenario, the Arctic could be ice-free for up to nine months by late this century.
“This would transform the Arctic into a completely different environment, from a white summer Arctic to a blue Arctic,” Jahn said in a statement. “So even if ice-free conditions are unavoidable, we still need to keep our emissions as low as possible to avoid prolonged ice-free conditions.”
The study was published in the peer-reviewed journal Nature Reviews Earth & Environment.
[and for the polar bears]
As ice melts, polar bears scrounge for food
It’s not easy to swim 109 miles when you’re starving to death. It’s not easy either to try to survive when you’re shedding body weight at a rate of 2.2 lb. a day. And it might be the hardest—or at least most tragic—of all if you’re a nursing mom and your calorie intake has dropped so low that you can no longer produce the milk you need to care for your young.
As a new paper in Nature Communications reveals, all of those challenges and more are facing the world’s polar bears, thanks to vanishing sea ice in our warming world, denying the animals a platform that they need to hunt for seals. If the trend isn’t reversed soon, the estimated 26,000 polar bears in the wild could start to lose their hold on survival before the middle of this century.
The researchers were less interested in establishing the fact of the bears’ food plight; scientists are already aware of that problem. What they were more focused on learning was both how gravely the nutritional loss is affecting the animals’ health and the alternative food sources they’re scrounging for on land.
To do their work, the scientists followed 20 different polar bears in Manitoba, Canada, from 2019 to 2022, fitting them with GPS trackers and video collars and periodically tranquilizing them to analyze, among other things, their blood, body mass, and daily energy expenditure—basically a measure of calories coming in vs. calories going out.
“The polar bears in Hudson Bay are probably at the edge of the range at which they can survive right now,” says Anthony Pagano, a research biologist with the U.S. Geological Survey and the lead author of the paper. “Most of the modeling work suggests that around 2050, they are going to be on land and away from their primary habitat [on the ice].” The contraction in range of the Hudson Bay community is likely to be reflected in the ranges of the 18 other polar-bear subpopulations scattered throughout the Arctic as well.
ACROSS THE ARC of the study, the data gathered was troubling. Weight loss varied among bears, with the daily loss of 2.2 lb. representing an average; some of the subjects dropped up to 3.75 lb. every 24 hours. That may not seem like much when an adult male polar bear can tip the scales at 1,200 lb. and a female at 700 lb., but it can add up fast.
And with less available to eat, the hungry bears have to travel farther to find their next meal. A young female that swam approximately 109 miles set the record for the bears studied. These endurance swims in search of food are energy-intensive and often fruitless. The bears are efficient hunters when they’ve got the purchase of ice beneath them, but they are clumsy when they are going after seals and trying to swim at the same time.
That leaves them scavenging on land for foods they would not ordinarily eat—and getting little payoff for their efforts. “Polar bears are feeding on ducks and geese—catching them when they’re flightless and molting—as well as on their eggs,” Pagano says. Other foods on the desperate bears’ menus included berries and other vegetation, bones, antlers, and, in one case, a beluga-whale carcass. None of that fare is as calorie-rich as a steady diet of live, blubber-packed seals.
In the 1980s, polar bears were on land for about 110 days out of the year, with no need to eat terrestrial foods since the fat deposits they’d accumulate thanks to wintertime seal hunting were enough to carry them the rest of the year. Now they’re off the ice for 130 days on average. It’s a measure of the nutritional knife’s edge on which the bears operate that just 20 days can make the difference between whether they live and thrive—or starve and die.
OLIVIER MORIN—AFP/GETTY IMAGES
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