The extent of sea ice blanketing the Arctic this winter fell to the lowest level on record, researchers announced this week; an ominous signal about the effects of climate change in the world’s fastest-warming region.
March is usually the peak season for Arctic sea ice; after months of ceaseless polar darkness, conditions are frigid and much of the ocean is frozen over. But just 5.53 million square miles of ice had formed as of March 22 this year - the smallest maximum extent in the 47-year satellite record, according to the National Snow and Ice Data Center. Since then, the ice has already begun to melt again.
“Sea ice is acting like the old canary in the coal mine,” Dartmouth University geophysicist Don Perovich said. “It’s saying loud and clear that warming is occurring.”
The record comes at a grim time for ice in all corners of the globe. In Antarctica, which has historically been more isolated from the effects of human-caused warming, sea ice shrank this month to the second-lowest extent on record. Research published in the journal Nature in February found that Earth’s glaciers are dwindling at an accelerating rate.
In the Arctic, this year’s maximum ice extent was 31,000 square miles smaller than the previous record, Perovich said - representing enough lost ice to cover the entire state of South Carolina. Compared to the 1981-2010 average, the missing ice area is greater than California, Texas and Washington combined.
The losses come amid rapidly warming conditions in the far north, where temperatures this February were as much as 22 degrees Fahrenheit above average, according to NSIDC. In the past four decades, research shows, the Arctic has heated up four times faster than the rest of the globe.
That’s because dwindling sea ice is both a sign of climate change and can drive further warming, explained Melinda Webster, a sea ice scientist at the University of Washington.
During winter, when the ocean is usually warmer than the surrounding air, sea ice acts as an insulating blanket, preventing heat from escaping into the atmosphere. In the summer, when the sun’s radiation shines down on the Arctic for 24 hours a day, the ice acts as a shield, reflecting more than half of the light that hits it back into space.
“We need the sea ice to act like an air conditioning unit for the planet,” Webster said.
With so little sea ice in the Arctic this year, more sunlight will be able to reach the open ocean, which absorbs more than 90 percent of the radiation that hits it. This will further warm the region, accelerating ice melt and exposing even more water to the light.
This feedback loop helps explain the rapid warming of the Arctic, and it is expected to lead to a complete lack of summer sea ice in the region within decades, Webster said. The consequences would be dire for seals, polar bears and other wildlife, which depend on a stable sea ice platform to birth their young and hunt for food. It would also expose miles of coastline to pounding ocean waves, accelerating the erosion that threatens to tip some communities into the sea.
But the effects will also be felt in places far from the poles, Perovich said. Studies suggest that a complete loss of Arctic sea ice would raise global temperatures as much as adding a trillion tons of carbon dioxide to the atmosphere. Changes in the Arctic could also affect the jet stream, the river of winds that flows through the upper atmosphere, contributing to more extreme weather around the globe.
“What happens in the Arctic doesn’t stay in the Arctic,” Perovich said.