On April 14, a group of NASA scientists were flying over the Beaufort Sea, north of Alaska and the Canadian border, when they saw something puzzling: Three holes in the sea ice with what look like rings around them and some wavy ice to their left.
“I don’t recall seeing this sort of thing elsewhere,” John Sonntag, a meteorologist with NASA who took the above photo, said in a statement.
At first glance, it may look like the frigid equivalent of crop circles, but scientists are pretty sure that in this case there’s a simple explanation. “My first guess is that these are seal breathing holes,” says Walt Meier, an atmospheric scientist at the National Snow and Ice Data Center who focuses on sea ice.
Harp and ring seals have been known to make these kinds of holes in thinner Arctic sea ice, and then use those holes repeatedly to come up for air.
For that theory to hold, there needs to be a good explanation for why the sea ice in this particular spot is thin enough for the seals to break through. Meier says these holes could be the result of warmer water coming in from the nearby Mackenzie delta, the shallow outpouring of the Mackenzie river from the nearby Canadian coast.
According to Meier, warmer water from the river flows into the ocean, and then, because warm water is less dense than cold water, it naturally floats to the surface in plumes.
That, in turn, thins out the ice at the surface, and could have drawn seals to the spot since the sea mammals more likely to pick spots to come up for air where the ice is already thin.
There are formations near the holes that look like waves, which the scientists say could be the result of water sloshing over the edges—a sign that warm water was rising up through the holes.
On their own, these holes don’t tell us all that much about the Arctic sea environment. They’re more spectacle than anything else, Meier says. But they do point to a trend in sea ice in general.
The photo above shows ice with evidence of “finger rafting”—which is when the wind pushes together two ice sheets, causing them to overlap like clasped hands.
The likeliest explanation, says Meier, is higher Arctic temperatures. In the past—as recently as the 1980s, sea ice in the region would be thick enough to withstand the southern winds that begin to blow north at the start of the winter.
But in recent years, thanks to warmer Arctic waters, the ice tends to be less stable and more easily blown away by the wind. Then, over the winter, the exposed water freezes‚ but only into thin sheets.
Those thin sheets are more likely to get blown together, creating the “finger rafting” phenomenon, and to be susceptible to melting due to plumes of warm river water from the shores. “In recent years, how often that happens and the scale of [this pattern] is much more than it used to be,” Meier says.
It’s impossible to directly connect this photo—just one data point—to climate change or warming Arctic waters. However, the photo does suggest that future research in the region may find a trend of diminishing ice over these waters.