Here's another entry in the parade of sobering climate change records: The National Snow and Ice Data Center announced Wednesday that Arctic sea ice hit its maximum extent for the year on March 7, and it was the lowest in the 38 years of satellite records.
The total ice coverage as the winter drew to a close was 471,000 square miles less than the 1981-2010 average—meaning ice larger than the combined size of California, Oregon, Washington and Nevada failed to form this year.
"We have had three record-setting low years of maximum sea ice extent in a row," said Walter Meier, a research scientist specializing in sea ice at NASA's Goddard Space Flight Center.
After decades of expansion, the sea ice surrounding Antarctica, where the summer is just ending, also hit a record low, NSIDC reported. Its minimum extent for year was reached on March 3, and was roughly 900,000 square miles below the 1981-2010 late-summer average.
The Arctic has seen a steady stream of new records, as both January and February saw record-low ice levels and the region has simmered in record high temperatures throughout the coldest part of the year.
In the five months from October 2016 and February 2017, air temperature over the Arctic Ocean was more than 2.5 degrees Fahrenheit above the 1981-2010 average, the NSIDC reports. In large parts of the northern Chukchi and Barents Seas, temperatures were twice as high.
In the last two winters, the region has also been hit by massive storms, which are rare in wintertime, Meier said. Storms feed on moisture and heat in the ocean, so when they hit the usually icy Arctic, they normally lose energy as moisture dries up.
But now there is less ice, and what ice remains is thinner. So storms can reach further north, breaking up ice as they go.
"Are these storms just a part of an usual year? Or are we starting to see some change occurring?" Meier said. "In the past, these were more like once-a-decade storms. Now we've seen at least four of them in the last year and a half or so."
It's not just the extent of ice that researchers are finding alarming—it's the volume, too. The University of Washington's ice-ocean model, which incorporates observations of weather conditions, found ice volume in the Arctic is unusually low.
"Usually the ice gets very thin in the summer," said Jinlun Zhang, an oceanographer at the university's Polar Science Center. "After that, in the fall and winter, the ice will grow like crazy. But this year, it's been so warm, the ice didn't really grow like we usually see."
Typically, it's the summer sea ice levels that climate scientists keep a close eye on, watching to see whether the ice's low point is going to break a record and by how much. The opening up of the Arctic Ocean in summertime as the ice vanishes has major ramifications for the rest of the globe, because with less ice, the ocean absorbs more energy from the sun. And that warming can impact the jet stream and extreme weather systems for the lower latitudes.
"The balance between the cold Arctic and the lower latitudes help defines our weather system," said Meier, who says to think about the Arctic ice as Earth's refrigerator. "As we change that, we're opening the refrigerator door and all of a sudden we're changing a big part of the climate system.
Though the winter sea ice levels are also trending down, the losses have been less severe. It's a time when the Arctic is dark and when there is less life—the phytoplankton isn't blooming and fewer animals are roaming around the ice.
"The winter has been a time we have kind of ignored," said Meier. "But maybe it is becoming more important."
Though the winter ice levels don't have a direct impact on summer levels—those will ultimately be impacted by factors like summer weather and wind patterns—what's happening now sets the stage for what's to come.
"The Arctic is a very variable place. It varies from year to year naturally," Meier said. "What we're doing now with anthropogenic warming, though, is we're putting a thumb on the scale. We're loading the dice to make warmer conditions more likely."