Alaska, a rapidly changing realm, will never cease to amaze Rick Thoman, a veteran climate scientist at the Alaska Center for Climate Assessment and Policy — even after a year of broken heat records and unprecedented losses of ice.
Now in the deep of fall, Alaska’s profound change continues. Record warm ocean temperatures mean that sea ice in the state’s northern waters is at historic lows for early November. The ice refuses to regrow.
“For old-timers like me, till the day I die, my jaw will drop at the sight of this stuff,” Thoman said.
“It has been a remarkable freeze-season (or lack of) so far,” noted Zack Labe, a climate scientist and PhD candidate at the University of California, Irvine. “Overall, the last month has featured large areas of open water north of Alaska and Siberia.”
The stagnant ice growth is most apparent in the Chukchi Sea, above and to the west of Alaska’s northernmost town of Utqiaġvik, which is, appropriately, also experiencing record warm air temperatures. Back in the cooler 20th century, sea ice would usually be present beyond Utqiaġvik’s shores.
But this early November, the main pack ice is still some 400 miles away.
The slow freeze-up can be largely blamed on exceptionally warm ocean waters, emphasized Thoman. “We’ve got these incredibly warm seas,” he said.
How warm? The Chukchi Sea had its warmest June through September temperatures on record. Meanwhile, the Bering Sea, which has had a dismal show of sea ice all year, experienced its warmest May through September on record, Thoman said.
This means that instead of bright, white ice reflecting sunlight back into space, the dark open oceans were able to absorb bounties of warmth for months on end. “This summer we had an early melt and record low sea ice coverage in the Chukchi Sea,” explained Lars Kaleschke, a sea ice researcher at the Alfred Wegener Institute’s Helmholtz Centre for Polar and Marine Research. “Consequently, the ocean could store more heat in its upper layers, which now delays the ice formation.”
These warm, open oceans must release this heat before ice can form. The waters will need to drop to about 28.5 degrees Fahrenheit — the freezing point of salty ocean water — to do that. When it comes to growing sea ice, simply frigid temperatures won’t cut it. “Thirty-five [Fahrenheit] may sound cold, but that’s not enough to make ice,” Thoman said.
These ice-free portions of ocean are a conspicuous consequence of a vicious cycle in the Arctic, called “Arctic amplification,” wherein the warming ocean melts ice, which then allows the oceans to grow even warmer. This, in turn, inhibits sea ice growth.
In large part, Arctic amplification is why the 13 lowest sea ice extents in the 40-year satellite record have all occurred in the last 13 years.
Alaska isn’t the only Arctic region now experiencing stagnant sea ice regrowth. Overall, Arctic sea ice is struggling. “The growth is well behind schedule in other areas,” noted Kaleschke. “The total ice extent is very low for the date, in fact, the second-lowest after 2016.”
“[Total sea ice extent] remains well below average,” added Labe. “This is contributing to the long-term Arctic amplification trend.”
Diminished sea ice and toppled records aren’t just one of the clearest indications of a rapidly changing climate; the warming Arctic also impacts powerful weather systems around the planet. There’s growing evidence that a warmer Arctic results in stagnant weather patterns, like the remarkable fall heat wave in the U.S. that occurred in late September and early October.
The lost sea ice has profound impacts for Alaskans, too. “Not only is sea ice important for their livelihoods, but it also acts as a barrier against coastal erosion from strong storm systems in the North Pacific,” said Labe.
A continually warming Arctic, however unpleasant, is a long-term trend and likely a prominent actor in the planet’s future, at least this century. “This is because of climate change mainly caused by human emission of greenhouse gases like CO2,” said Kaleschke.
Earth’s atmospheric carbon dioxide emissions are now skyrocketing. CO2 levels haven’t been this high in at least 800,000 years — though more likely millions of years. What’s more, carbon levels are now rising at rates that are unprecedented in both the geologic and historic record.