Siberia’s Heat Wave Triggered an Arctic Sea Ice Melt

A heat wave brought tropical temperatures and fires to Arctic Siberia last month. Now, it’s causing sea ice to crater.

Jul 21 2020, 1:51pmSnap

For the past month, Siberia has captured the world’s attention thanks to a climate change-fueled heat wave that caused temperatures in an Arctic town to crack 100 degrees in June and whipped up an outbreak of fires across normally frigid tundra. But an equally alarming situation is unfolding just north of Siberia’s shores: sea ice is crashing in a region that scientists consider to be the ice factory of the Arctic.

In fact, there’s so little ice cover in the Laptev Sea north of Siberia—as well as the Barents Sea to the west—that ice cover across the entire Arctic Ocean is currently at its lowest mid-July extent on record. If sea ice continues to plummet, it could bottom out at a new record low in September. Even if 2020 doesn’t set a dubious new record, the ongoing ice annihilation is yet another sign that the Arctic is undergoing unprecedented changes as it heats up at more than twice the globally averaged rate.

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“We’re kind of in the middle this year of this grand experiment,” said Mark Serreze, the director of the National Snow and Ice Data Center. That experiment, he explained, consists of a mix of regional and global factors fueling remarkable ice losses.

One of those factors traces back to the winter. In February, the polar vortex, a belt of upper atmosphere winds that encircles the Arctic, approached record strength. This altered airflow at Earth’s surface and triggered a record positive phase of an air pressure pattern known Arctic Oscillation (AO). When the AO is positive, strong winds blow northward off the Siberian coast, pushing ice into the central Arctic Ocean.

“These winds move old ice away from the coast and create regions of very thin ice near the coast,” Andrea Lang, an associate professor of atmospheric sciences at the University of Albany, told Motherboard in an email. “Very thin ice melts and gives way to open ocean earlier in the warm season than older multi-year ice.”

That’s especially true when there’s plenty of heat and sunlight available to melt the ice in the spring. For Siberia, there’s been no shortage of either: from January to June, temperatures across a vast swath of the region were running 9 degrees Fahrenheit above average, part of an extremely prolonged and intense heat spell that would have been “almost impossible” without climate change, according to a recent analysis by climate researchers with the World Weather Attribution project.

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The heat reached its apex in mid-June, when a ridge of high pressure air sent temperatures soaring north of 100 degrees Fahrenheit in the Russian town of Verkhoyansk—a record for the entire Arctic region. It was around that time that Siberian sea ice, awash in both heat and sunlight associated with the same weather pattern, “really dropped off a cliff,” said Zack Labe, a climate scientist at Colorado State University.

Since then, the meltdown has accelerated. The high pressure ridge behind Siberia’s heat wave migrated north into the central Arctic Ocean, Labe says, causing temperatures to soar up to 18 degrees Fahrenheit above average. During the first half of July, warm weather and unrelenting sun (the far north is bathed in near round-the-clock light at this time of year) caused the Arctic to shed roughly 56,000 square miles of ice, an area larger than New York state, every day. The fires raging across Arctic Siberia might have played a role as well by depositing soot on sea ice, darkening it and allowing it to absorb more of the sun’s energy, Serreze said.

As of Monday, sea ice had all but vanished from Siberian waters, and Arctic-wide levels were on par with September annual minima in the 1990s.

The melt season is far from over, though, and it’s not clear whether ice will hit a new record low this September, a title currently held by 2012. If the Arctic moves into a cloudier, stormier, weather pattern, Labe says, melting “could easily slow down,” similar to how it did last August when cooler weather pumped the brakes on sea ice losses after the ice had veered into record territory earlier in the season. (2019 wound up effectively tying 2007 and 2016 for second-lowest sea ice extent on record.)

Then again, the most intense Arctic storms could shake things up in a different direction. Arctic cyclones, which are fueled by the temperature gradient between warm continents and cold Arctic ice, reach their peak in the central Arctic ocean in late summer. These storms can be potent destroyers of sea ice, particularly if that ice was already weakened by melting. Evidence suggests that 2012’s record minimum was partly thanks to a monster cyclone that spun up over Siberia that August.

Whether 2020 brings a new record for sea ice destruction or not, what’s happening this year will be significant. Most new sea ice formation in the Arctic occurs along the eastern half of Siberia’s north coast, where ice grows in the autumn and winter before being swept out to sea. Because there’s so much open water absorbing sunlight in the region right now, Serreze says it’s “very likely” that autumn ice formation will be delayed, which could have ripple effects going into next year.

Ultimately, more years like this could hasten Arctic sea ice’s long term, climate change driven meltdown, which matters far more than individual records.

“Everyone wants to focus on the minimum, but any amount of time the ice is at a record low is affecting arctic climate,” Labe said. “To me, that’s very significant.”

Tagged:

News, ice, climate change, siberia, fire, Heat Wave, worldnews, world climate

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