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Warming at the poles will soon be felt globally in rising seas, extreme weather

F6 2010 - "Massive chunk of ice breaks off Greenland glacier"

Ice loss, permafrost thaw, fires: Trouble in the Arctic and Antarctic could cause shocks
to the world’s weather and sea levels sooner than thought, says a new study.

IMAGE: Arctic tundra lakes spread out across the soggy Yamal Peninsula in northwest Siberia, Russia.
Photograph by Jeffrey Kerby

By Cheryl Katz
PUBLISHED December 4, 2019

Eric Post has observed seasons at the same location on the West Greenland tundra for 26 years. Over that time, he’s seen profound changes. When he first started working there, hundreds of caribou covered the hills. Now, he says, the herd is down to around 90.

“You find yourself thinking they’ll be back next spring; numbers will go up again,” Post says, “but year after year goes by and the big groups just aren’t there the way they used to be.”

As Earth trudges steadily toward a dangerously warm future, a new report on the outlook for the polar regions says the Arctic is already there—with consequences on the horizon for everyone.

“There is a real possibility that we will be entering a phase of accelerated Arctic warming in the next two to four decades if mitigation action isn’t taken soon,” says Post, a climate change ecologist at the University of California, Davis.

Post is lead author of the report published today in Science Advances .. Arctic tundra lakes spread out across the soggy Yamal Peninsula in northwest Siberia, Russia.
Photograph by Jeffrey Kerby , in which an international group of scientists looks at current and future impacts of polar warming across a range of disciplines.

The Arctic is warming far more quickly than anywhere else on the planet. Temperatures climbed nearly 1.8 degrees Fahrenheit (1 Celsius) in the past decade alone. At the current rate of greenhouse gas emissions, the North is on track to warm 7.2 F (4 C) year-round—and top 12.6 F (7 C) in autumns—by the middle of this century, according to the report. That’s about when the planet as a whole is projected to reach the 3.6 F (2 C) warming often cited as the threshold for disastrous impacts.

(Find out why Earth’s climate systems are heading for dangerous tipping points
https://www.nationalgeographic.com/science/2019/11/earth-tipping-point/ .)

[...]

Rising concerns

Sea-level rise is another looming concern. Arctic land ice—particularly the vast ice sheet atop Greenland—is thawing faster than current climate models suggest, and could raise sea levels substantially more than the 3 feet projected by the end of the century in the Intergovernmental Panel on Climate Change’s report released in September.

Arctic permafrost thaw is also escalating, releasing the potent greenhouse gas methane and spiking atmospheric levels, with profound global warming effects.

[...]

Meanwhile, warming is already knocking the Arctic’s seasonal clock off-kilter. Spring plant growth is coming earlier and earlier, meaning tundra animals like the caribou at Post’s Greenland research site arrive at their annual birthing grounds after the plants they eat have passed their nutritional peak. Flowers open before the insects that pollinate them can get there, and migrating birds miss the spring flush. The shifts are accelerating, the report says, and in future could exceed ecosystems’ ability to adapt.

Arctic warming also stands to disrupt the marine food web, increase mortality for polar bears and seals, and threaten the livelihoods of the region’s indigenous people. One bright note in the outlook: So far whales seem to be benefitting from range expansion as sea ice recedes.

The Antarctic is not the Arctic

While temperatures are surging in the Arctic—by century’s end, they could soar as much as 23.4 F (13 C) during parts of the year, according to the report—Antarctic warming has been similar to the global average, although some parts are warming much faster.

https://www.nationalgeographic.com/science/2019/12/arctic/