In the deep middle of the remote Arctic Ocean, things are amiss.
With the passage of summer, the ice — diminished by the warm season — is expected to regrow as frigid temperatures envelope the Arctic.
But, this year, it's not.
Specifically, sea ice in the Central Arctic basin — a massive region of ocean some 4.5 million square kilometers in size — hasn't started its usual rapid expansion, and unusually warm temperatures in both the air and the ocean are largely to blame.
"For the most part, Arctic sea ice normally begins rapidly refreezing this time of year," Zack Labe, a climate scientist and Ph.D. candidate at the University of California Irvine, said over email.
— Lars Kaleschke (@seaice_de) October 7, 2018
The air over the high Arctic is anomalously warm compared to the decades-long average, Lars Kaleschke, an Arctic scientist at the University of Hamburg's Center for Earth System Research and Sustainability, said over email. In mid-October, the temperatures here should be plummeting. But they've gone up.
While temperatures are still hovering near freezing in these high northern realms, they're presently around a whopping 18 degrees Fahrenheit (10 degrees Celsius) above the 1958 to 2002 average for this time of year.
A formidable mass of high atmospheric pressure stretching all the way from Alaska to the North Pole has pushed relatively warm air from the North Pacific Ocean into the Arctic, noted Labe.
But warmth in the oceans is likely playing a significant role, too.
"Both the ocean and atmosphere are warmer than usual," said Kaleschke.
It's difficult, however, to know whether it's warm air or ocean waters that are playing a stronger role in suppressing the growth of ice in this remote Arctic sea, said Kaleschke.
Image: National Snow and Ice Data Center
Yet, oceans can absorb much more heat than the air — in fact, over 90 percent of Earth's accumulating heat from global warming gets trapped in the absorbent seas.
This process is accelerated in the Arctic Ocean, a place warming at two to three times the rate of the rest of the planet.
"I tend to suspect the ocean heat [is] delaying the ice growth more than the atmosphere but this is just a guess," said Kaleschke.
These days, the reality that strange events are occurring in the Arctic shouldn't be too surprising.
— Zack Labe (@ZLabe) October 7, 2018
"Arctic climate changes and extremes are now happening during all seasons of the year," said Labe.
"The last several autumns have all featured well-above average temperatures and low levels of Arctic sea ice."
Separately from Kaleschke, Labe did his own analysis of both the central Arctic and portions of surrounding seas, finding similarly stark results.
While the Central Arctic Basin might be the largest regional sea in the greater Arctic, other portions of this northern ocean are seeing the expected, rapid build-up of ice.
— Zack Labe (@ZLabe) October 9, 2018
But for now, unusual circumstances in the central Arctic will persist, although an influx of cooler air might steer things back to normal.
"A change in the weather conditions could easily allow sea ice to begin growing more rapidly, but for the time being, the unusually warm temperatures (relative to average) and slow sea ice refreeze will continue," said Labe.
On Tuesday, ice in the Central Arctic Basin was the second lowest in recorded history for that day of the year, noted Kaleschke.
"Only in the year 2007 there was less ice in the Central Arctic," said Kaleschke.