Climate scientists have hypothesized for decades that melting sea ice at the North Pole hastens global warming by decreasing the amount of heat from the sun that’s reflected back into space. More dark ocean and less snow-covered ice equals less reflection—makes sense, right?
While researchers developed models to demonstrate how this could happen, its occurrence has never been confirmed by data—until now.
According to a new study conducted at the Scripps Institution of Oceanography in San Diego, between 1979 and 2011 the average levels of Arctic albedo—the technical term for the fraction of solar energy reflected from Earth’s surface—decreased from 52 percent to 48 percent.
Here’s the problem: Reduced albedo creates a feedback loop. Higher temperatures lead to less albedo lead to higher temperatures lead to less albedo…and so on. And the observed percentage is twice as much as model-based studies had forecast.
“That is big—unexpectedly big,” said Ian Eisenman, a climate scientist and coauthor of the study, which was published in the journal Proceedings of the National Academy of Sciences.
Just how big? The amount of heat produced by this loss in albedo is equal to “roughly 25 percent of the average global warming currently occurring due to increased carbon dioxide levels,” reports Live Science.
Since 1983, the North Pole has warmed more than any other place on the planet. In 2012, the Arctic ice cap shrank to a record low, when ice there covered only a quarter of the Arctic Ocean. That’s a 50 percent drop from 1979, when NASA first began monitoring the area with satellites.
“There are a lot of questions right now as to why the ice is retreating as fast as it is, and why it has the structure that it has is a little hard to say,” Eisenman told Live Science.
One reason, the Scripps researchers believe, is that their study indicates that white cloud cover in the area might not have as much to do with the ocean’s loss of reflective power as previously thought. “Changes in cloudiness appear to play a negligible role,” they write.
Not all hope should be lost, according to Eisenman. While the Arctic Ocean may not be able to restore the same amount of ice it had more than 30 years ago, some cover could return this century—though to what extent is unclear, he said.
Currently, the parts of the Arctic Ocean near Alaska and Siberia are being affected most by melting ice, Eisenman told New Scientist.
He emphasized that his team’s research is far from complete.
“I think this is an important part of the climate change story, but there are also lots of other pieces we need.”