The Earth's reflectivity is diminishing faster than researchers previously believed.
As sea ice cover is lost the Earth's surface becomes less reflective, making it "darker," a Scripps Institute of Oceanography news release reported. This darkening causes the Earth to absorb more solar energy.
Since the 1970s the Arctic has warmed by 3.6 degrees Fahrenheit; this has caused the summer minimum of sea ice cover to decrease by 40 percent causing the area to be less reflective or decreasing its "albedo."
Albedo is measured by percentage; a completely black surface has an albedo of zero percent while a perfectly white region would be measured at 100 percent. The albedo of fresh snow usually measures between 80 and 90 percent while the ocean's surface only measures at 40 percent.
The albedo of the Arctic is believed to have fallen from 52 to about 48 percent since 1979.
"It's fairly intuitive to expect that replacing white, reflective sea ice with a dark ocean surface would increase the amount of solar heating," Scripps graduate student Kristina Pistone, said in the news release. "We used actual satellite measurements of both albedo and sea ice in the region to verify this and to quantify how much extra heat the region has absorbed due to the ice loss. It was quite encouraging to see how well the two datasets - which come from two independent satellite instruments - agreed with each other."
The study is the first to use "direct satellite measurements" to look at the albedo changes linked to the diminishing ice cover. The researchers found the surface darkening is happening about two to three times more serious than past studies have suggested.
"Scientists have talked about Arctic melting and albedo decrease for nearly 50 years," Veerabhadran Ramanathan, "a distinguished professor of climate and atmospheric sciences," said in the news release. "This is the first time this darkening effect has been documented on the scale of the entire Arctic."
